A nutritionist’s guide to choosing supplements
Walk into any pharmacy or browse online, and it's easy to feel overwhelmed by the sheer number of supplements available. From different brands and dosages to an ever-growing list of formulations, choosing the right one can feel like a minefield. Magnesium alone is available in more than ten different forms, each with its own properties and potential uses. Should you choose folic acid or methylfolate? Is vitamin D3 better than D2? Are premium supplements really worth the extra cost, or is it just clever marketing?
These are some of the questions I hear most often in clinic, and they're important ones. While many supplements contain the same nutrient on the label, the form it comes in can influence how well it is absorbed, how it behaves in the body, how well it is tolerated and, in some cases, what it's most useful for. Choosing the wrong form may not necessarily be harmful, but it could mean you're spending money on a product that isn't the best fit for your health goals or individual needs.
At the same time, it's important to remember that supplements are exactly that - supplements. They are designed to supplement a healthy diet, not replace one. Wherever possible, I advocate a food-first approach, as whole foods provide not only vitamins and minerals but also fibre, healthy fats, protein and thousands of beneficial plant compounds that work together to support health. However, there are many situations where supplements can play a valuable role, whether that's correcting a nutrient deficiency, supporting pregnancy, complementing dietary restrictions or helping meet increased nutritional demands.
Key Takeaways
Supplements can be valuable tools, but they are not a replacement for a healthy diet. The foundations of health remain a varied, nutrient-dense diet, adequate protein, good sleep, regular movement and stress management.
The best supplement is the one you actually need. More supplements do not necessarily mean better health. Targeted supplementation is usually more effective than taking multiple products without a clear purpose.
The form of a nutrient matters. Different forms can vary in absorption, effectiveness and tolerability. For example, vitamin D3 is generally preferred over vitamin D2, magnesium glycinate is often better tolerated than magnesium oxide, and creatine monohydrate remains the most evidence-backed form of creatine.
Quality matters more than price. An expensive supplement is not automatically superior. Look for evidence-based ingredients, appropriate doses, transparent labelling and reputable manufacturing standards.
Look beyond marketing claims. Supplements should be supported by human research, ideally including randomised controlled trials and systematic reviews, rather than relying solely on testimonials or trends.
Correct deficiencies, don't just chase symptoms. Fatigue, hair loss, digestive issues and poor concentration can have many causes. Identifying and addressing the underlying reason is often more valuable than adding another supplement.
Contents:
Why supplement form matters
Do expensive supplements work better?
Supplements 101:
Vitamin D
Magnesium
Iron
Folate vs folic acid
Vitamin B12
Omega-3
Probiotics
Collagen
Creatine
How to choose a quality supplement
When supplements may not be enough
Frequently asked questions
Why Does Supplement Form Matter?
Not all supplements are created equal. While two products may contain the same vitamin or mineral on the label, the form in which that nutrient is supplied can influence how well it is absorbed, how easily it is tolerated and, in some cases, the role it plays in the body.
This is known as bioavailability - the proportion of a nutrient that is absorbed and becomes available for the body to use. Some forms are more readily absorbed than others, while some are chosen because they are gentler on the digestive system or have been studied for specific health outcomes.
That doesn't necessarily mean the "best" form is always the most expensive one. The most appropriate choice depends on your individual health, symptoms, medical history and goals.
Some of the key factors that can differ between supplement forms include:
Absorption (bioavailability) Some forms are absorbed more efficiently than others, meaning more of the nutrient may be available for the body to use.
Digestive tolerance Certain forms are less likely to cause side effects such as constipation, diarrhoea or stomach upset.
Clinical application Different forms may be better suited to particular situations. For example, magnesium citrate is commonly used to support constipation, whereas magnesium glycinate is often chosen by those looking for a well-tolerated form.
Stability Some nutrients are more chemically stable than others, helping to preserve their potency throughout a product's shelf life.
Cost Higher-quality forms can sometimes be more expensive to manufacture, although a higher price doesn't automatically mean a better supplement.
It's also worth remembering that absorption doesn't depend solely on the supplement itself. Factors such as your digestive health, age, medications, existing nutrient status and whether you take a supplement with food can all influence how much your body is able to utilise. For example, reduced stomach acid, coeliac disease, inflammatory bowel disease and some medications may affect the absorption of certain nutrients.
This is one reason why nutrition should always be personalised. The supplement that works well for one person may not be the best choice for someone else.
Does a More Expensive Supplement Mean It's Better?
The short answer is: not necessarily.
It's easy to assume that a higher price tag means a better product, but that's not always the case. Whilst some premium supplements justify their cost through higher-quality ingredients, superior formulations or rigorous quality testing, others may simply be more expensive because of branding or marketing.
Rather than focusing solely on price, it's more helpful to consider what you're actually paying for.
A well-formulated supplement should contain an evidence-based dose of the active ingredient, use a form that is appropriate for its intended purpose and be manufactured to high quality standards.
For example, a magnesium glycinate supplement is likely to cost more than magnesium oxide because the raw ingredient itself is more expensive to produce. However, research suggests magnesium glycinate is generally better absorbed and better tolerated, making it a worthwhile investment for some people. Similarly, the cheapest iron supplement isn't always the most cost-effective if it causes constipation or stomach upset and you stop taking it. In these situations, paying slightly more for a better-tolerated form may improve adherence and ultimately be better value.
Quality also extends beyond the active ingredient. Some supplements contain unnecessary fillers, artificial colours, sweeteners or proprietary blends that make it difficult to know exactly what you're taking. Whilst these ingredients aren't always harmful, I generally recommend choosing products with transparent labelling and as few unnecessary additives as possible.
Another important consideration is third-party testing. Reputable manufacturers voluntarily test their products to verify that they contain the ingredients listed on the label, are free from contaminants and meet quality standards. This can provide greater confidence in the product, particularly for nutrients where potency and purity are important, such as omega-3 supplements.
It's also worth considering the evidence behind the supplement itself. Some nutrients and formulations have been evaluated in multiple randomised controlled trials (RCTs) - considered one of the highest-quality study designs for assessing the effectiveness of an intervention - while others have little robust research to support the claims made about them. This doesn't necessarily mean a newer or less-studied supplement is ineffective, but it does mean we should interpret marketing claims with caution. Where possible, I recommend choosing supplements that have been investigated in well-designed human studies and are supported by a broader body of scientific evidence, rather than relying on testimonials or influencer recommendations alone.
That said, spending more doesn't automatically guarantee a better supplement. Some supermarket own-brand products offer excellent value and contain appropriate doses in well-researched forms. Equally, some premium products may include ingredients with limited evidence or make claims that aren't supported by robust research.
Ultimately, the best supplement is one that is:
Appropriate for your individual needs and health goals
In a form that is well absorbed and suitable for your circumstances
Provided at an evidence-based dose
Manufactured by a reputable company with good quality control
One that you can take consistently
If you're unsure which supplement is right for you, it's worth seeking personalised advice. A healthcare professional can help determine whether you need a supplement at all, which form is most appropriate and whether there may be an underlying cause that also needs addressing. In many cases, optimising your diet, lifestyle or investigating the root cause of symptoms can have a greater impact than adding another supplement to your routine.
Supplements 101: Vitamin D
Vitamin D is one of the most commonly recommended supplements, particularly in the UK where sunlight is limited for much of the year. It's best known for supporting healthy bones and teeth by helping the body absorb calcium and phosphorus, but it also plays important roles in immune function, muscle health and cell signalling.
Although we can obtain small amounts of vitamin D from foods such as oily fish, egg yolks and fortified products, the majority is produced in the skin following exposure to sunlight. During the autumn and winter months in the UK, UVB rays are not strong enough for us to make adequate vitamin D, which is why the NHS recommends that everyone considers taking a daily vitamin D supplement between October and early March. Some groups - including people with darker skin tones, those who spend little time outdoors or cover most of their skin, older adults, and people who are pregnant or breastfeeding - may benefit from supplementation all year round.
Vitamin D2 vs Vitamin D3: What's the difference?
Vitamin D supplements are usually available in two forms:
Vitamin D2 (ergocalciferol) - derived from plant sources and fungi.
Vitamin D3 (cholecalciferol) - usually derived from lanolin (sheep's wool), although vegan forms sourced from lichen are now widely available.
Both forms can help raise vitamin D levels, but research suggests that vitamin D3 is generally more effective at increasing and maintaining blood concentrations of vitamin D over time. For this reason, vitamin D3 is typically the preferred choice for most people when supplementing.
Should you take vitamin D with food?
Yes. Vitamin D is a fat-soluble vitamin, meaning it is absorbed more effectively when taken alongside a meal containing some healthy fats. This could be as simple as taking it with breakfast containing eggs, yoghurt, nuts or avocado, or with your main meal of the day.
How much vitamin D do you need?
The NHS recommends that adults and children over the age of one consider taking 10 micrograms (400 IU) of vitamin D daily during the autumn and winter months.
However, individual requirements can vary. Some people with confirmed deficiency, certain medical conditions or reduced absorption may require higher doses under the guidance of a healthcare professional. As vitamin D is fat-soluble and stored in the body, taking very high doses for prolonged periods without medical supervision is not recommended. The safe upper limit for adults is 100 micrograms (4,000 IU) per day, unless a higher dose has been specifically recommended and monitored by a healthcare professional.
Do you need vitamin K2?
Vitamin D and vitamin K2 are often sold together, and you'll frequently see claims that they should always be taken in combination. Vitamin K2 plays an important role in directing calcium towards bones and teeth and away from soft tissues, and there is biological rationale for the two nutrients working together.
However, the evidence is still evolving, and current UK guidelines do not recommend that everyone taking vitamin D also needs supplemental vitamin K2. If you eat a varied diet containing foods such as green leafy vegetables, cheese or fermented foods, you may already be obtaining adequate vitamin K. It's also important to note that people taking anticoagulant medications such as warfarin should seek medical advice before taking vitamin K supplements.
Practical tips
When choosing a vitamin D supplement, consider the following:
Choose vitamin D3 (cholecalciferol) unless you require a vegan alternative, in which case lichen-derived vitamin D3 is widely available.
Take it with a meal containing some fat to support absorption.
Follow NHS guidance unless you've been advised otherwise by a healthcare professional.
If you've been diagnosed with vitamin D deficiency or have ongoing symptoms that could be related to low vitamin D, speak to your GP or healthcare practitioner about whether testing is appropriate before taking higher-dose supplements.
Whilst vitamin D is one of the most evidence-supported supplements available, it's still important to remember that more isn't always better. The right dose and formulation should reflect your individual health status, lifestyle and nutritional needs.
Supplements 101: Magnesium
Magnesium is an essential mineral involved in over 300 enzymatic reactions in the body. It plays a role in energy production, muscle and nerve function, blood sugar regulation, protein synthesis, bone health and normal psychological function. Despite its importance, many people fail to meet the recommended intake through diet alone.
Good food sources include green leafy vegetables, nuts, seeds, wholegrains, beans, lentils and dark chocolate. However, factors such as highly processed diets, certain medications, gastrointestinal conditions and increased physiological demands may contribute to lower magnesium status in some individuals.
Why are there so many different forms of magnesium?
Unlike vitamin D, magnesium is rarely found on its own in supplements. Instead, it is bound to another compound (known as a ligand), such as glycine, citrate or malic acid. This influences how well it is absorbed, how it behaves in the body and how likely it is to cause digestive side effects.
No single form is "best" for everyone. The right choice depends on why you're taking it.
Magnesium glycinate (bisglycinate)
Most suitable for general supplementation, those prone to digestive upset, supporting sleep and relaxationWell absorbed and generally gentle on the gut.
One of the forms I recommend most frequently in clinical practice.
Magnesium citrate
Most suitable for people with constipation
Well absorbed but may have a mild laxative effect, making it a useful option where constipation is also a concern.
Magnesium malate
Most suitable for: Supporting energy production and muscle function. Contains malic acid, which is involved in cellular energy production.
Some people prefer this form if fatigue is a prominent symptom, although evidence is still emerging.
Magnesium threonate (L-threonate)
Most suitable for: Cognitive health
Early research suggests it may cross the blood-brain barrier more effectively than other forms, although more high-quality human studies are needed before firm conclusions can be drawn.
Magnesium oxide
Most suitable for: Short-term relief of constipation
Contains a high amount of elemental magnesium but is relatively poorly absorbed. It is inexpensive and commonly found in over-the-counter supplements, but is more likely to cause diarrhoea than other forms.
How much magnesium do you need?
The UK Nutrient Reference Value (NRV) for magnesium is:
300 mg per day for adult men
270 mg per day for adult women
Most of this should ideally come from food rather than supplements.
There is no official UK upper limit for magnesium from food, as healthy kidneys are generally very effective at removing excess magnesium. However, high doses from supplements can cause diarrhoea, abdominal cramping and nausea, particularly when taken as magnesium oxide or citrate.
The European Food Safety Authority has established a tolerable upper intake level of 250 mg per day of magnesium from supplements alone (excluding magnesium obtained from food). Higher supplemental doses are sometimes used under the supervision of a healthcare professional where clinically appropriate.
Should you take magnesium at a particular time of day?
There is no strong evidence that magnesium is significantly more effective at one time of day than another. The most important factor is taking it consistently.
Some people prefer taking magnesium glycinate in the evening as part of their bedtime routine, while magnesium citrate may be better taken earlier in the day if it has a laxative effect. Taking magnesium with food can also improve tolerance in those with sensitive stomachs.
Who may benefit from magnesium supplementation?
Whilst routine supplementation isn't necessary for everyone, magnesium may be worth considering in people with an increased risk of low intake or deficiency, including those who:
Eat very few nuts, seeds, wholegrains or green vegetables
Have gastrointestinal conditions that impair nutrient absorption
Take medications such as proton pump inhibitors or certain diuretics
Consume high amounts of alcohol
Have increased physiological demands, such as some athletes or during pregnancy (under appropriate guidance)
As with all supplements, it's important to remember that magnesium isn't a cure-all. If you're experiencing symptoms such as muscle cramps, fatigue, headaches or poor sleep, these may have many possible causes. Supplementation may be appropriate in some cases, but identifying and addressing the underlying cause is often just as important.
Practical tips
When choosing a magnesium supplement:
For general supplementation: Magnesium glycinate (bisglycinate) is usually a good starting point due to its absorption and gastrointestinal tolerance.
For constipation: Magnesium citrate may be a more appropriate choice because of its mild osmotic effect.
Avoid choosing magnesium oxide simply because it contains more elemental magnesium - despite this, it is absorbed less efficiently than many other forms.
Check the label to see how much elemental magnesium each serving provides, as this can vary considerably between products.
As with any supplement, choose products from reputable manufacturers that provide transparent ingredient lists and appropriate dosing.
Supplements 101: Iron
Iron is an essential mineral that plays a vital role in transporting oxygen around the body. It is a key component of haemoglobin - the protein in red blood cells that carries oxygen from the lungs to tissues - and is also involved in energy production, immune function, cognitive performance and DNA synthesis.
When iron stores become depleted, the body is less able to transport oxygen efficiently, which can lead to symptoms such as fatigue, poor exercise tolerance, shortness of breath, headaches, dizziness and difficulty concentrating. More severe deficiency can result in iron deficiency anaemia.
Good dietary sources of iron include red meat, poultry, seafood, beans, lentils, tofu, fortified breakfast cereals, nuts, seeds and dark green leafy vegetables. However, iron from animal foods (haem iron) is generally absorbed more efficiently than iron from plant foods (non-haem iron).
Do you need an iron supplement?
Iron deficiency is one of the most common nutrient deficiencies worldwide, particularly among women of reproductive age. However, unlike some other nutrients, iron should not be supplemented routinely unless there is a clinical indication - i.e. a confirmed deficiency.
This is because excess iron can accumulate in the body and may be harmful. Symptoms such as fatigue can have many different causes, so it's important to establish whether low iron is actually the problem before starting supplementation.
If you suspect iron deficiency, speak to your GP or healthcare practitioner. A blood test measuring haemoglobin and iron status - often including ferritin, transferrin saturation and other markers where appropriate - can help determine whether supplementation is needed and whether there may be an underlying cause that requires investigation.
Different forms of iron
There are many different iron supplements available, and the form can make a significant difference to both absorption and digestive tolerance.
Ferrous bisglycinate A well-absorbed form that is generally better tolerated and less likely to cause constipation, nausea or stomach upset than many traditional iron salts. Often my preferred choice where supplementation is appropriate.
Ferrous sulphate One of the most commonly prescribed forms in the NHS. Effective and inexpensive but more commonly associated with gastrointestinal side effects such as constipation, nausea and abdominal discomfort.
Ferrous fumarate Another commonly prescribed iron salt. Similar effectiveness to ferrous sulphate but side effects can still occur in some people.
Ferrous gluconate Contains less elemental iron per tablet than ferrous sulphate but may be slightly better tolerated by some individuals.
Heme iron Derived from animal sources and generally well absorbed. Suitable for some people but not appropriate for vegetarians or vegans.
How much iron do you need?
The UK Reference Nutrient Intake (RNI) is:
8.7 mg per day for adult men
14.8 mg per day for women aged 19-50 years
8.7 mg per day for women over 50 years
The higher requirement in pre-menopausal women reflects iron losses during menstruation.
If iron deficiency has been diagnosed, much higher doses than the daily requirement are often prescribed for a limited period to replenish iron stores. The appropriate dose depends on the severity of the deficiency and should be determined by a healthcare professional.
How can you improve iron absorption?
If you're taking an iron supplement, a few simple strategies can help maximise absorption:
Take iron with a source of vitamin C, such as a glass of orange juice, kiwi fruit or berries, as vitamin C enhances the absorption of non-haem iron.
Avoid taking iron at the same time as tea or coffee, as the polyphenols they contain can reduce absorption.
Calcium supplements and dairy products may also interfere with iron absorption, so it's often best to take them at a different time of day.
Some medications, including antacids and proton pump inhibitors, can reduce iron absorption. If you're taking these regularly, discuss the timing of your supplements with your healthcare professional.
What if iron supplements upset your stomach?
Digestive side effects are one of the main reasons people stop taking iron supplements. Constipation, nausea, abdominal discomfort and dark stools are relatively common, particularly with ferrous sulphate.
If this happens, don't assume iron supplementation isn't an option. Sometimes switching to a different formulation, such as ferrous bisglycinate, reducing the dose temporarily or taking iron on alternate days (where appropriate and advised by your healthcare professional) can improve tolerance whilst maintaining effectiveness.
Treat the cause, not just the deficiency
Correcting iron deficiency is important, but it's equally important to understand why it developed in the first place.
Heavy menstrual bleeding is a common cause in pre-menopausal women, but other contributing factors may include low dietary intake, pregnancy, endurance exercise, frequent blood donation, gastrointestinal conditions such as coeliac disease or inflammatory bowel disease, or blood loss from the digestive tract. Persistent or unexplained iron deficiency should always be investigated by a healthcare professional.
Simply taking iron without addressing the underlying cause may allow the deficiency to return once supplementation stops.
Practical tips
When choosing an iron supplement:
Only supplement if iron deficiency has been confirmed or advised by a healthcare professional.
Ferrous bisglycinate is often a good option if gastrointestinal side effects have been an issue.
Take iron with vitamin C where possible and away from tea, coffee and calcium-rich foods.
Continue supplementation for the duration recommended by your healthcare professional, as iron stores often take longer to replenish than symptoms take to improve.
Arrange follow-up blood tests if advised to confirm that your iron levels have recovered and to ensure the underlying cause has been addressed.
Supplements 101: Folate vs Folic acid
Folate, also known as vitamin B9, is an essential nutrient involved in DNA synthesis, cell division and the production of healthy red blood cells. It is particularly important during periods of rapid growth, such as pregnancy, but also plays an important role in supporting normal brain function and maintaining healthy levels of homocysteine - an amino acid that has been associated with cardiovascular and cognitive health when elevated.
Although the terms folate and folic acid are often used interchangeably, they are not exactly the same.
What's the difference between folate and folic acid?
Folate is the naturally occurring form of vitamin B9 found in foods such as:
Green leafy vegetables
Lentils and beans
Chickpeas
Asparagus
Broccoli
Avocados
Citrus fruits
Folic acid is the synthetic form used in most supplements and fortified foods. After it is absorbed, the body converts folic acid into the biologically active forms that can be used by cells.
You'll also come across 5-methyltetrahydrofolate (5-MTHF) or methylfolate, which is the biologically active form of folate found in many practitioner-grade supplements.
Is methylfolate better than folic acid?
This is one of the most common questions I hear in clinic. Methylfolate is already in its active form and therefore doesn't require the same metabolic conversion as folic acid. Because of this, it's often marketed as being superior. However, for the vast majority of people, folic acid is highly effective, well researched and remains the recommended form for preventing neural tube defects during pregnancy.
Research suggests that methylfolate may be absorbed effectively and can raise folate status, but there is currently no convincing evidence that it is superior to folic acid for the general population.
In practice, both forms have a place. The most appropriate choice depends on the individual and the reason for supplementation.
What about the MTHFR gene?
You may have seen claims online suggesting that people with an MTHFR gene variant cannot process folic acid and should only take methylfolate. Whilst certain MTHFR variants can modestly reduce the activity of an enzyme involved in folate metabolism, these variants are common and most people continue to metabolise folic acid sufficiently to meet their needs.
Current UK guidance does not recommend routine genetic testing for MTHFR variants or advise avoiding folic acid on this basis alone. For most people, particularly those planning a pregnancy, folic acid remains the evidence-based recommendation.
If you have a known genetic variant, complex medical history or have been advised by your healthcare practitioner, methylfolate may be considered as part of an individualised approach.
Folate and pregnancy
Folate is essential before and during early pregnancy because it helps support the healthy development of the baby's brain and spinal cord.
The NHS recommends that anyone who is trying to conceive or who could become pregnant takes:
400 mcg of folic acid daily, starting at least three months before conception and continuing until 12 weeks of pregnancy.
Some women are advised to take a higher dose of 5 mg folic acid, but this should only be taken under medical supervision. This may be recommended if you:
Previously had a pregnancy affected by a neural tube defect
Have diabetes
Take certain anti-epileptic medications
Have conditions associated with reduced folate absorption
Have a BMI of 30 kg/m² or above
Always discuss higher-dose supplementation with your GP or maternity team.
Can you get too much folic acid?
Unlike naturally occurring folate from food, high intakes of folic acid from supplements can potentially mask the signs of vitamin B12 deficiency. Over time, untreated vitamin B12 deficiency can lead to irreversible neurological damage.
For this reason, the safe upper intake level for folic acid from supplements and fortified foods is 1,000 micrograms (1 mg) per day for adults, unless a higher dose has been prescribed by your doctor.
If you're experiencing symptoms such as fatigue, numbness, tingling or memory problems, it's important not to assume folate is the problem. A healthcare professional may recommend checking both folate and vitamin B12 levels before starting supplementation.
Practical tips
When choosing a folate supplement:
Eat plenty of folate-rich foods as the foundation of your intake.
If you're planning a pregnancy, choose a supplement providing 400 micrograms of folic acid, unless you've been advised to take a higher dose.
Methylfolate may be appropriate in some situations, but it is not routinely necessary for most people.
Avoid high-dose folic acid unless recommended by a healthcare professional.
If you're concerned about folate or vitamin B12 deficiency, speak to your GP or healthcare practitioner about appropriate blood testing before self-supplementing.
For most people, the debate around folate versus folic acid is far less important than ensuring adequate intake in the first place. A balanced diet, appropriate supplementation where needed and personalised advice remain the cornerstones of supporting optimal folate status.
Supplements 101: Vitamin B12
Vitamin B12 is an essential nutrient that supports the production of red blood cells, DNA synthesis and the normal functioning of the nervous system. It also plays a key role in energy metabolism and helps maintain healthy levels of homocysteine - an amino acid that has been linked with cardiovascular and cognitive health when elevated.
Unlike many other vitamins, vitamin B12 is found almost exclusively in animal-derived foods, including meat, fish, eggs and dairy products. As a result, people following vegetarian or vegan diets are at a greater risk of deficiency unless they consume fortified foods or take a supplement.
Who may benefit from vitamin B12 supplementation?
Vitamin B12 supplements are often recommended for:
Vegans
Vegetarians with a low intake of dairy or eggs
Older adults, as absorption tends to decline with age
People taking long-term metformin
People taking proton pump inhibitors (PPIs), such as omeprazole
Those with gastrointestinal conditions that affect absorption, including coeliac disease, Crohn's disease or following gastric surgery
People diagnosed with pernicious anaemia (under medical supervision)
Vitamin B12 deficiency can develop gradually over months or even years because the liver stores several years' worth of the vitamin. Early symptoms can be vague and may include:
Fatigue
Brain fog
Poor concentration
Pins and needles
Numbness
Memory problems
Low mood
Weakness
Left untreated, severe vitamin B12 deficiency can lead to irreversible nerve damage, highlighting the importance of early diagnosis and appropriate treatment.
Different forms of vitamin B12
Cyano-cobalamin The most widely studied, stable and inexpensive form. It has excellent evidence for preventing and correcting deficiency in most people.
Methyl-cobalamin The biologically active form involved in several metabolic pathways. Often marketed as superior, although current evidence suggests it offers little additional benefit over cyanocobalamin for most individuals.
Hydroxo-cobalamin Commonly used as an intramuscular injection within the NHS to treat deficiency because it remains in the body for longer than other forms.
Adenosyl-cobalamin Another active form involved in energy metabolism. Less commonly used in supplements and currently supported by less clinical evidence than cyanocobalamin.
Is methylcobalamin better than cyanocobalamin?
Many premium supplements promote methylcobalamin as the "best" form of vitamin B12 because it is already biologically active. Whilst this sounds appealing, research has not consistently demonstrated that methylcobalamin is superior to cyanocobalamin for preventing or treating vitamin B12 deficiency in most healthy individuals. Cyanocobalamin has been extensively studied, is highly stable and is effective at restoring vitamin B12 status when taken appropriately.
For most people, the dose and consistency of supplementation are likely to be more important than choosing between these two forms.
How much vitamin B12 do you need?
The UK Reference Nutrient Intake (RNI) for adults is:
1.5 micrograms per day
However, supplements often contain much higher doses - commonly between 50 and 1,000 micrograms. This is because only a small proportion of vitamin B12 is absorbed through passive diffusion, particularly in people with impaired absorption.
Vitamin B12 has a very low potential for toxicity, and no tolerable upper intake level has been established, as excess amounts are generally excreted in the urine.
What if you're deficient?
If vitamin B12 deficiency is suspected, it's important to identify the underlying cause rather than simply taking a supplement.
Your GP can arrange blood tests to assess vitamin B12 status, often alongside folate and a full blood count. In some cases, additional tests such as methylmalonic acid (MMA) or holotranscobalamin may help clarify borderline results, although these are not routinely performed within the NHS.
Treatment depends on the cause of the deficiency.
For example:
Dietary deficiency can often be corrected with oral supplements.
Pernicious anaemia, where the body cannot absorb vitamin B12 because it lacks intrinsic factor, usually requires lifelong vitamin B12 injections.
People with gastrointestinal disorders or following bariatric surgery may also require higher doses or injectable treatment.
If you have symptoms suggestive of vitamin B12 deficiency, avoid self-diagnosing. Prompt assessment is important because neurological complications become more difficult to reverse the longer they are left untreated.
Practical tips
When choosing a vitamin B12 supplement:
If you follow a vegan diet, regular supplementation is strongly recommended.
Cyanocobalamin is an effective, evidence-based and cost-effective option for most people.
Choose a reputable manufacturer with transparent ingredient lists and appropriate dosing.
If you're experiencing symptoms of deficiency, arrange appropriate testing before starting high-dose supplementation where possible.
If you have pernicious anaemia or another condition affecting vitamin B12 absorption, follow the treatment plan recommended by your GP or specialist.
Vitamin B12 is one of the few nutrients that can become deficient even in people eating an otherwise healthy diet, particularly if absorption is impaired. Fortunately, when recognised early and managed appropriately, deficiency is usually straightforward to correct.
Supplements 101: Omega-3
Omega-3 fatty acids are a group of essential fats that play important roles throughout the body. They form part of every cell membrane and are involved in brain function, vision, heart health, inflammation, immune function and normal growth and development.
Unlike some fats, the body cannot produce omega-3s in sufficient quantities, so they must come from the diet or, where appropriate, supplements.
The three main types of omega-3 are:
EPA (eicosapentaenoic acid) - involved in supporting cardiovascular health and helping to regulate inflammatory processes.
DHA (docosahexaenoic acid) - a major structural component of the brain and retina, making it particularly important during pregnancy and early life.
ALA (alpha-linolenic acid) - found in plant foods such as flaxseeds, chia seeds and walnuts. Although ALA is an essential fatty acid, the body converts only a small proportion into EPA and DHA.
Should you take an omega-3 supplement?
The best way to increase your omega-3 intake is through food. The NHS recommends eating at least two portions of fish each week, including one portion of oily fish, such as:
Salmon
Mackerel
Anchovies
Sardines
Herring
Trout
If you don't eat oily fish regularly, follow a vegetarian or vegan diet, or have increased requirements, an omega-3 supplement may help bridge the gap.
Fish oil vs algal oil
Most omega-3 supplements are derived from either fish or marine algae.
Fish oil naturally contains both EPA and DHA and has been the subject of the majority of clinical research.
Algal oil provides DHA and, depending on the product, varying amounts of EPA. It is a suitable vegan alternative and is produced directly from the marine algae that fish consume.
Both can be effective options - the best choice depends on your dietary preferences and health goals.
Triglyceride vs ethyl ester: does the form matter?
If you've looked closely at omega-3 supplements, you may have noticed terms such as triglyceride (TG) or ethyl ester (EE).
These describe the chemical form of the oil.
Triglyceride (TG) and re-esterified triglyceride (rTG) forms are closer to the structure naturally found in fish.
Ethyl ester (EE) forms are commonly used during the manufacturing process because they are less expensive to produce.
Some studies suggest triglyceride forms may be absorbed slightly more efficiently than ethyl esters, particularly when taken without food. However, when omega-3 supplements are taken alongside a meal containing fat, the difference in absorption appears to be relatively small.
In practice, the overall quality of the supplement, the amount of EPA and DHA it provides and whether you take it consistently are likely to be more important than the specific chemical form.
How much omega-3 do you need?
Unlike many vitamins and minerals, there is no official UK Reference Nutrient Intake (RNI) for EPA and DHA.
For general health, many organisations recommend aiming for around 250-500 mg of combined EPA and DHA per day, which can usually be achieved by eating oily fish once or twice a week.
Higher intakes may sometimes be recommended for specific clinical situations, but these should be discussed with a healthcare professional, particularly if you take blood-thinning medication.
Is more always better?
Not necessarily. Whilst omega-3 supplements are generally considered safe, taking very high doses without medical supervision isn't recommended. High-dose fish oil may increase the risk of side effects in some individuals, including indigestion, fishy aftertaste and, at very high intakes, a potential increase in bleeding risk.
More isn't always better - it's about taking an appropriate dose for your individual needs.
How do you choose a good-quality omega-3 supplement?
Not all fish oils are created equal. Omega-3 fats are delicate and can become oxidised when exposed to heat, light or oxygen. Oxidised oils may have an unpleasant smell or taste and are thought to provide fewer health benefits.
When choosing a supplement, look for one that:
Clearly states the amount of EPA and DHA, rather than just the total amount of fish oil.
Is manufactured by a reputable company with rigorous quality control.
Has been independently tested for purity and contaminants such as heavy metals.
Is stored in dark or opaque packaging to help protect the oil from oxidation.
Is within its expiry date and stored according to the manufacturer's instructions.
Practical tips
When choosing an omega-3 supplement:
Aim to meet your needs through oily fish where possible.
If supplementing, choose a product that clearly states its EPA and DHA content.
Vegetarians and vegans should consider an algal oil supplement containing DHA, with EPA if available.
Take omega-3 supplements with a meal containing fat to optimise absorption.
If you take anticoagulant medication or have a bleeding disorder, speak to your GP or healthcare professional before starting high-dose omega-3 supplements.
Omega-3 supplements can be a useful addition for people who don't regularly eat oily fish or have increased nutritional requirements. However, as with all supplements, they're most effective when used alongside an overall healthy dietary pattern rather than as a substitute for one.
Supplements 101: Probiotics
Probiotics are live microorganisms which, when consumed in adequate amounts, may confer a health benefit to the host. Put simply, they are beneficial bacteria or yeasts that can help support the balance and function of the gut microbiome.
The gut microbiome is home to trillions of microorganisms that play important roles in digestion, immune function, vitamin production, metabolism and the gut-brain axis. When this ecosystem becomes disrupted - sometimes referred to as dysbiosis - it has been associated with a range of digestive and wider health concerns. Whilst probiotics aren't a cure-all, research suggests that specific strains may be beneficial in certain situations.
Are all probiotics the same?
No. This is one of the biggest misconceptions surrounding probiotic supplements. Different probiotic strains have different properties and have been studied for different health outcomes. Choosing a probiotic simply because it contains the highest number of bacteria or the longest list of strains isn't necessarily the best approach.
A probiotic should always be chosen based on the specific strain and the evidence supporting its intended use. For example, a probiotic that has been studied in antibiotic-associated diarrhoea may not be appropriate for someone with IBS or recurrent urinary tract infections.
What do all the names mean?
Probiotics are identified by three parts:
Genus - for example Lactobacillus or Bifidobacterium
Species - for example rhamnosus or longum
Strain - for example GG or BB536
The strain is particularly important because this is what has been evaluated in clinical studies.
For example:
Lacticaseibacillus rhamnosus GG
Bifidobacterium animalis subsp. lactis BB-12®
Two probiotics may belong to the same species but behave very differently if they are different strains.
Do more CFUs mean a better probiotic?
CFU stands for colony-forming units, which estimates the number of live microorganisms in a probiotic. It's easy to assume that more is better, but that's not necessarily true.
A probiotic containing 50 billion CFU isn't automatically more effective than one containing 10 billion CFU. What matters more is whether the strain has been shown to be effective for the condition you're trying to support, and whether the dose used matches that investigated in clinical trials.
How do you choose a good probiotic?
If selecting a probiotic, look for a product that:
Clearly lists the genus, species and strain of each microorganism.
States the number of live CFUs at the end of shelf life, not just at the time of manufacture.
Has been evaluated in human clinical trials.
Is produced by a reputable manufacturer with appropriate quality control.
Has clear storage instructions where required.
When might probiotics be helpful?
Research suggests that certain probiotic strains may be beneficial in specific situations, including:
Supporting recovery after a course of antibiotics
Helping reduce the risk of antibiotic-associated diarrhoea
Some symptoms of irritable bowel syndrome (IBS)
Supporting gut health during travel
Certain inflammatory bowel conditions, under specialist guidance
Some aspects of vaginal health
However, the evidence varies considerably depending on the condition and the probiotic strain being used. There is no single probiotic that has been shown to benefit every health concern.
Are probiotics safe?
For most healthy people, probiotics are considered safe and are generally well tolerated.
Some people notice a temporary increase in bloating or changes in bowel habits during the first few days of taking a probiotic as the gut microbiome adapts. These symptoms are usually mild and settle within a week or two.
However, probiotics are not appropriate for everyone. People who are severely immunocompromised, critically ill or have central venous catheters should only take probiotics under medical supervision because, although rare, there is a small risk of infection.
Food first
Before reaching for a probiotic supplement, it's worth remembering that your daily diet has a far greater influence on the gut microbiome than any single capsule.
Eating a diverse range of plant foods, consuming enough fibre and including fermented foods such as live yoghurt, kefir, kimchi or sauerkraut where appropriate can help support a healthy and resilient gut microbiome. Equally important are the prebiotics - fibres that nourish your existing beneficial gut bacteria. Foods such as onions, garlic, leeks, oats, legumes and slightly green bananas provide these important substrates.
For many people, improving dietary habits may have a greater impact on long-term gut health than taking a probiotic alone.
Practical tips
When choosing a probiotic:
Choose a product based on your specific health goal, not simply the highest CFU count.
Look for supplements that clearly state the genus, species and strain.
Buy from reputable manufacturers that provide evidence supporting their formulations.
Follow the storage instructions carefully, as some probiotics require refrigeration while others are shelf-stable.
If your symptoms persist despite taking a probiotic, it may be worth investigating whether an underlying issue - such as coeliac disease, inflammatory bowel disease, food intolerances or other gastrointestinal conditions - could be contributing.
Probiotics can be a valuable tool in the right circumstances, but they are just one piece of the puzzle. In my clinical practice, I always consider the wider picture, including diet, lifestyle, medications, stress, sleep and the potential root causes of digestive symptoms, rather than relying on probiotics alone.
Supplements 101: Collagen
Collagen has become one of the most popular supplements in recent years, with claims that it can improve everything from skin elasticity and hair health to joint pain and muscle recovery. Whilst some of these claims are supported by emerging research, others are less well established. Collagen is the most abundant protein in the human body, making up around one-third of our total protein. It provides structure and strength to the skin, bones, tendons, ligaments, cartilage and blood vessels.
From our mid-20s onwards, our natural collagen production gradually begins to decline. Factors such as ageing, smoking, excessive UV exposure, poor diet and menopause can accelerate this process, contributing to wrinkles, reduced skin elasticity and changes in joint health over time.
What is collagen made from?
Collagen supplements are typically produced from:
Bovine (cow)
Marine (fish)
Porcine (pig)
Chicken (primarily type II collagen)
Most supplements contain hydrolysed collagen peptides (also known as collagen hydrolysate). During manufacture, collagen is broken down into smaller peptides, making it easier to digest and absorb.
At least 28 different types of collagen have been identified, although only a handful are commonly found in supplements.
Type I: Skin, bones, tendons and ligaments
Type II: Cartilage and joints
Type III: Skin, muscles and blood vessels
Many collagen supplements contain a combination of Types I and III, while products marketed for joint health often contain Type II collagen.
Does collagen actually work?
The evidence for collagen supplementation is growing, although it's important to keep expectations realistic.
Research suggests that daily supplementation with hydrolysed collagen peptides for around 8-12 weeks may improve skin hydration and elasticity, with some studies also reporting modest reductions in wrinkle depth. However, the size of these benefits varies between studies and more long-term research is needed.
There is also evidence that collagen supplementation, particularly when combined with resistance exercise, may support joint comfort and connective tissue health in some individuals. Some studies have reported improvements in joint pain, particularly in physically active people and those with osteoarthritis, although results are not consistent across all populations.
At present, there is less convincing evidence that collagen supplements significantly improve hair growth or nail strength, despite these being common marketing claims.
Is marine collagen better than bovine collagen?
Marine collagen is often marketed as being superior because it contains smaller peptides and is predominantly Type I collagen. However, there is currently limited evidence to suggest that marine collagen is consistently more effective than bovine collagen. Most of the available research has investigated hydrolysed collagen peptides rather than comparing different animal sources directly.
The quality of the supplement, the amount of collagen provided and consistent use are likely to be more important than whether it comes from fish or cattle.
How much collagen should you take?
Most studies showing potential benefits have used 2.5-15 g of hydrolysed collagen peptides per day, depending on the health outcome being investigated.
For skin health, doses of around 2.5-10 g daily are commonly studied, while research into joint and connective tissue health often uses 5-15 g daily.
There is no established upper safe limit for collagen supplementation, and it is generally considered safe for healthy adults. Mild digestive symptoms, such as bloating or a feeling of fullness, are the most commonly reported side effects.
Do you need vitamin C?
Vvitamin C plays an essential role in the body's own collagen production. Whilst many collagen supplements now include vitamin C, it's also easy to obtain adequate amounts through food. Citrus fruits, berries, kiwi, peppers and broccoli are all excellent sources. Without sufficient vitamin C, the body cannot produce collagen effectively, regardless of how much collagen you consume.
Food first
Collagen supplements can be a useful addition for some people, but they shouldn't replace the foundations of a nutritious diet.
To support your body's natural collagen production:
Eat adequate protein throughout the day.
Include plenty of vitamin C-rich fruit and vegetables.
Consume foods rich in zinc and copper, which also contribute to collagen synthesis.
Avoid smoking and excessive UV exposure, both of which accelerate collagen breakdown.
Practical tips
When choosing a collagen supplement:
Look for hydrolysed collagen peptides, as these are the forms most commonly used in research.
Choose a product that clearly states the amount of collagen per serving.
Consider the collagen type based on your goals - Types I and III are most commonly used for skin, whilst Type II is typically used for joint health.
Take collagen consistently for at least 8-12 weeks, as this is the timeframe investigated in most clinical trials.
Ensure your overall diet provides enough protein and vitamin C, as collagen supplements work best as part of a broader nutritional approach.
Collagen supplements may offer modest benefits for skin and joint health in some people, but they are not a substitute for a healthy lifestyle. As with any supplement, the greatest benefits are likely to be seen when they complement a balanced diet, regular exercise, adequate sleep and other healthy habits rather than replacing them.
Supplements 101: Creatine
Creatine is one of the most extensively researched sports supplements available, with decades of evidence supporting its safety and effectiveness. Whilst it's often associated with bodybuilders and elite athletes, research over the past decade has highlighted potential benefits that extend far beyond the gym, including healthy ageing, brain health and supporting women through different stages of life.
Creatine is a naturally occurring compound made from three amino acids - arginine, glycine and methionine. Around 95% of the body's creatine is stored in our muscles, where it helps regenerate adenosine triphosphate (ATP) - the body's primary source of energy for short, high-intensity activities.
We obtain creatine from foods such as red meat and fish, but the amounts are relatively small. For this reason, vegetarians and vegans often have lower muscle creatine stores and may experience a greater response to supplementation.
What does creatine do?
Creatine helps replenish ATP more rapidly during short bursts of intense exercise, making it particularly beneficial for activities involving repeated high-intensity efforts, such as:
Resistance training
Sprinting
Tennis
Football
Rugby
CrossFit
High-intensity interval training (HIIT)
By improving the body's ability to produce energy during these activities, creatine supplementation has been shown to support improvements in strength, power output, training capacity and lean muscle mass when combined with appropriate exercise.
Increasingly, research also suggests creatine may play a role in:
Supporting healthy ageing by helping preserve muscle mass and strength
Recovery from resistance training
Bone health indirectly through improved muscle function
Cognitive performance during periods of sleep deprivation or high mental demand
Supporting women's health during menstruation, pregnancy, postpartum and menopause, although more research is needed in these areas
Which form of creatine is best?
Walk into a supplement shop and you'll find dozens of different creatine products, including creatine hydrochloride (HCl), buffered creatine, creatine ethyl ester and creatine gummies, each claiming to be superior.
However, the evidence is remarkably consistent. Creatine monohydrate remains the gold standard.
It is the form used in the vast majority of clinical trials, has consistently demonstrated excellent safety and effectiveness, and is usually the most affordable option. Other forms are often significantly more expensive, yet there is little convincing evidence that they lead to greater muscle uptake, improved performance or fewer side effects than creatine monohydrate.
How much creatine should you take?
For most people, a daily dose of 3-5 g of creatine monohydrate is sufficient to gradually saturate muscle creatine stores over several weeks.
Some people choose to complete a loading phase of around 20 g per day, divided into four doses, for 5-7 days before switching to a maintenance dose of 3-5 g daily. This increases muscle stores more quickly but is not essential. Taking 3-5 g daily without loading will achieve similar muscle saturation after approximately three to four weeks. Consistency is far more important than timing.
Should you take creatine before or after exercise?
Research suggests that the exact timing of creatine has very little impact on its effectiveness. The most important factor is taking it every day, including on rest days, to maintain saturated muscle stores. Many people find it easiest to take creatine with a meal or after training simply because it helps establish a consistent habit.
Does creatine cause water retention?
One of the biggest myths surrounding creatine is that it causes bloating. Creatine does increase water content inside muscle cells, which is actually part of how it works. This is different from the type of fluid retention that causes swelling or puffiness under the skin. Some people notice a small increase in body weight during the first few weeks of supplementation as muscle creatine stores increase, but this reflects increased intracellular water rather than fat gain.
Is creatine safe?
Creatine is one of the most thoroughly studied supplements available and is considered safe for healthy individuals when taken at recommended doses. Extensive research has found no evidence that creatine damages healthy kidneys or liver. However, people with existing kidney disease or other significant medical conditions should seek advice from their healthcare professional before starting supplementation.
Minor digestive symptoms can occasionally occur, particularly if large doses are taken at once. Dividing the dose or sticking to 3-5 g daily usually resolves this.
Practical tips
When choosing a creatine supplement:
Choose creatine monohydrate - it has the strongest evidence base and is usually the most cost-effective option.
Aim for 3-5 g daily.
A loading phase is optional rather than essential.
Take it consistently, including on rest days.
Stay well hydrated, particularly during periods of intense training.
If you're a competitive athlete, choose a supplement that has been independently tested for banned substances through programmes such as Informed Sport.
Creatine is one of the few supplements that consistently delivers on its promises. Whilst it's best known for improving strength and exercise performance, the emerging evidence for healthy ageing, women's health and cognitive function makes it an increasingly interesting supplement beyond the world of sport. As always, it should complement - not replace - a balanced diet, regular exercise and good lifestyle habits.
How to Choose a High-Quality Supplement
1. Choose the right supplement for your needs.
Before thinking about brands or formulations, ask yourself whether you need a supplement in the first place. The best supplement is one that addresses a genuine nutritional need or has an evidence-based role for your specific health goal. For example, someone with iron deficiency may benefit from an iron supplement, whereas someone with normal iron levels is unlikely to.
Where possible, avoid taking supplements simply because they're trending on social media or recommended by influencers. More isn't always better, and unnecessary supplementation can sometimes be ineffective, expensive or even harmful.
2. Look for evidence-based ingredients
Not all supplements have the same level of scientific evidence behind them. Look for ingredients that have been investigated in well-designed human studies, ideally including randomised controlled trials (RCTs) and systematic reviews. Whilst no single study provides all the answers, supplements supported by a consistent body of research are generally a more reliable choice than those relying on anecdotal claims alone.
Be cautious of products making dramatic promises such as "detox", "boost your metabolism" or "burn fat fast". If a claim sounds too good to be true, it probably is.
3. Consider the form of the nutrient
As you've read, the form of a nutrient can influence how well it is absorbed and tolerated. For example:
Vitamin D3 is generally preferred over vitamin D2.
Magnesium glycinate is often better absorbed and better tolerated than magnesium oxide.
Ferrous bisglycinate may cause fewer gastrointestinal side effects than ferrous sulphate.
Creatine monohydrate remains the best-studied form of creatine.
Choosing the most appropriate form can often make a greater difference than choosing the most expensive product.
4. Check the dose
A supplement isn't necessarily better because it contains more of a nutrient. Some products provide doses that are too low to be effective, while others contain unnecessarily high amounts that exceed recommended upper limits without clear evidence of additional benefit. Compare the amount provided with current UK guidance or the dose used in clinical research, and remember that more isn't always better.
5. Choose reputable manufacturers
Quality control matters. Reputable manufacturers should clearly state:
The amount of each active ingredient.
The form of the nutrient.
Full ingredient lists.
Batch numbers and expiry dates.
Where possible, choose companies that follow Good Manufacturing Practice (GMP) standards and are transparent about their sourcing and manufacturing processes.
6. Look for third-party testing
Unlike medicines, food supplements are not routinely tested before reaching the market. Some manufacturers voluntarily submit their products for independent testing to verify that they:
Contain the ingredients listed on the label.
Provide the stated dose.
Are free from contaminants such as heavy metals or harmful microorganisms.
Independent certification can provide additional reassurance, particularly for supplements such as omega-3 oils or for competitive athletes who require products screened for banned substances.
7. Read beyond the marketing
The front of the label is designed to sell the product. Turn the bottle over and look at the Supplement Facts panel instead. Ask yourself:
Does it tell you the exact dose?
Does it state the specific form of the nutrient?
Are there unnecessary fillers or proprietary blends that hide ingredient amounts?
Does the product make exaggerated health claims?
Transparent labelling is often a sign of a reputable manufacturer.
8. Remember that supplements complement a healthy diet
No supplement can compensate for a poor diet, chronic stress, inadequate sleep or a lack of physical activity. A supplement should do exactly what its name suggests - supplement an already balanced lifestyle.
Whenever possible, prioritise:
A varied, minimally processed diet.
Plenty of fruit and vegetables.
Adequate protein.
Wholegrains, legumes, nuts and seeds.
Regular movement.
Good sleep.
Stress management.
These foundations will almost always have a greater impact on long-term health than adding another supplement.
A quick checklist
Before buying a supplement, ask yourself:
✔ Do I actually need it?
✔ Is there good scientific evidence supporting its use?
✔ Is it the most appropriate form for my needs?
✔ Does it provide an evidence-based dose?
✔ Is it made by a reputable manufacturer?
✔ Has it been independently tested where appropriate?
✔ Am I using it to complement, rather than replace, a healthy diet and lifestyle?
If you're unsure, it's worth seeking personalised advice. A registered nutrition professional can help determine whether a supplement is appropriate, identify potential nutrient deficiencies and, perhaps most importantly, investigate whether there's an underlying cause that also needs addressing. In many cases, identifying and treating the root cause of symptoms will have a greater impact than simply adding another supplement to your routine.
When Supplements May Not Be Enough
Supplements can be incredibly useful when they're used appropriately. They can help correct nutrient deficiencies, support periods of increased nutritional demand and complement a healthy diet. However, they are not a substitute for identifying and addressing the underlying cause of symptoms.
In clinic, I often meet people who have accumulated a cupboard full of supplements in the hope that the next one will finally make them feel better. Whilst supplements certainly have their place, persistent symptoms such as fatigue, digestive problems, hair loss or low mood often require a more thorough investigation.
For example, low iron levels may be caused by heavy menstrual bleeding, coeliac disease or inflammatory bowel disease. Vitamin B12 deficiency may reflect poor dietary intake, but it could also indicate pernicious anaemia or impaired absorption. Similarly, ongoing bloating may not improve with probiotics alone if the underlying issue is IBS, coeliac disease, food intolerances or small intestinal bacterial overgrowth (SIBO).
Rather than continually adding more supplements, it's worth asking a more important question: why has this problem developed in the first place?
A root-cause approach may involve exploring factors such as:
Dietary quality and nutrient intake
Digestive health and nutrient absorption
Hormonal changes
Medications that affect nutrient status
Chronic stress and sleep
Physical activity levels
Underlying medical conditions
Blood test results where appropriate
Sometimes the answer is simply improving the quality and variety of the diet. Other times, targeted blood tests or referral to your GP for further investigation may be needed. Identifying the underlying cause not only makes treatment more effective but may also reduce the need for long-term supplementation.
It's also worth remembering that supplements don't work in isolation. Even the highest-quality supplement is unlikely to compensate for an overall dietary pattern that's lacking in essential nutrients, poor sleep, chronic stress or a sedentary lifestyle. The biggest improvements in health usually come from getting the foundations right first.
If you've been taking supplements consistently but your symptoms persist, or you find yourself continually adding new products without seeing much benefit, it may be time to seek personalised advice. A comprehensive assessment can help determine whether you're taking the right supplements, whether further testing is appropriate and, most importantly, whether there is an underlying issue that needs to be addressed.
My approach is always food first, supplement second. Supplements should support your health - not become a substitute for understanding it.
FAQs
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There isn't a single "best" magnesium for sleep, but magnesium glycinate (bisglycinate) is often the preferred choice. It is well absorbed, gentle on the digestive system and contains glycine - an amino acid that may promote relaxation. While research on magnesium and sleep is mixed, some studies suggest supplementation may improve sleep quality in people with low magnesium levels or poor sleep. It's important to remember that sleep is influenced by many factors, including stress, caffeine intake, light exposure and sleep habits, so supplements work best alongside good sleep hygiene.
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Both vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) can increase vitamin D levels, but research suggests vitamin D3 is generally more effective at raising and maintaining blood concentrations over time. For this reason, vitamin D3 is usually the preferred form for supplementation. If you follow a vegan diet, lichen-derived vitamin D3 is now widely available and offers an effective plant-based alternative.
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Not necessarily. Folic acid remains the recommended form for women trying to conceive and during early pregnancy, as it has the strongest evidence for reducing the risk of neural tube defects. Methylfolate is the biologically active form of folate and may be appropriate in some situations, but current evidence does not show it is routinely superior for the general population. The best choice depends on your individual circumstances and should be discussed with a healthcare professional if you're unsure.
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Ferrous bisglycinate is generally better tolerated than traditional iron salts such as ferrous sulphate and is less likely to cause constipation, nausea or stomach discomfort. However, everyone's digestive system responds differently. If you've experienced side effects with iron supplements in the past, speak to your healthcare professional before stopping treatment, as switching to a different formulation may improve tolerance.
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The answer depends on your diet, health, lifestyle and medical history. Some supplements, such as vitamin D during the winter months, are recommended for many people. Others should only be taken when there is a clear need, such as a diagnosed deficiency or increased nutritional requirement. If you're experiencing persistent symptoms such as fatigue, hair loss, digestive issues or recurrent infections, it's worth speaking to your GP or a qualified nutrition professional. In some cases, blood tests or further investigation may be appropriate before starting supplements.
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Not always. Whilst many supplements are safe when taken appropriately, taking multiple products increases the risk of exceeding recommended upper limits, duplicating ingredients or interacting with medications. For example, excessive vitamin A can be harmful during pregnancy, and high-dose iron should only be taken when clinically indicated. Before starting several supplements, review the ingredients carefully and seek professional advice if you're taking prescription medication or have an underlying health condition.
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Healthy skin and hair depend on far more than a single supplement. A balanced diet rich in protein, essential fats, vitamins and minerals provides the building blocks needed for normal skin and hair growth. If a nutrient deficiency is present - such as iron, zinc, vitamin D or vitamin B12 - correcting it may improve symptoms. There is also emerging evidence that hydrolysed collagen peptides may modestly improve skin hydration and elasticity, although the benefits tend to be modest and require consistent use. Before investing in expensive beauty supplements, it's worth considering whether an underlying nutritional deficiency or medical condition could be contributing to your symptoms.
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The NHS recommends that women who are trying to conceive or are pregnant take 400 micrograms of folic acid daily from at least three months before conception until 12 weeks of pregnancy, alongside 10 micrograms (400 IU) of vitamin D daily. Some women may require higher-dose folic acid under medical supervision. Depending on dietary intake and individual circumstances, additional nutrients such as iodine, vitamin B12 (particularly for vegans) or omega-3 DHA may also be appropriate. It's best to discuss supplementation with your midwife, GP or healthcare practitioner to ensure it's tailored to your needs.
About the author
Laura Andreli, Nutritional Therapist
Laura helps clients unlock the powerful connection between the gut and the brain. She specialises in IBS, SIBO, digestive disorders, food sensitivities, and the gut–brain axis - particularly where symptoms such as brain fog, anxiety, low mood, fatigue, and poor concentration may be linked to underlying microbiome imbalance and metabolic stress.
Laura uses evidence-informed nutrition strategies and targeted lifestyle interventions to support digestive function, calm neuroinflammation, and improve energy, mood, and cognitive performance.
Laura’s path into nutritional therapy is personal. While studying at Cambridge, she was diagnosed with Polyendocrine Metabolic Ovarian Syndrome (PMOS; formerly termed PCOS). The experience of receiving a label without clear, actionable guidance shaped her philosophy: translate complex science into practical steps that genuinely help people feel and function better. A former England-level long jumper, she understands first-hand how hormones, metabolism, and nutrition can influence performance, recovery, and cognition.
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