Do Nutritional Supplements Work?

Walk into almost any health shop, browse social media or search online for ways to improve your health and you’ll quickly find yourself surrounded by supplements.

Multivitamins, protein powders, creatine, collagen, magnesium, vitamin D, omega-3, probiotics, “fat burners”, greens powders and countless other products all promise to make us healthier, stronger, leaner or more energetic.

But how many of them do we actually need?

The answer is perhaps less exciting than the supplement industry would like us to believe.

For most healthy people, a varied, balanced diet should provide the vast majority of the nutrients the body needs. Supplements cannot compensate for a poor diet, inadequate exercise or an unhealthy lifestyle.

However, that doesn’t mean all supplements are useless. A handful have good scientific evidence behind them, particularly for people who exercise regularly, older adults, people with restricted diets and those with a diagnosed nutritional deficiency.

So let’s separate the science from the marketing.

What exactly is a nutritional supplement?

A dietary or nutritional supplement is simply a product designed to add something to your normal diet.

That might include:

vitamins and minerals

protein powders

amino acids

creatine

omega-3 fatty acids

herbal extracts

probiotics

collagen

sports-performance supplements

The important word here is supplement.

They should supplement a good diet rather than replace one.

Fruit, vegetables, whole grains, pulses, nuts, dairy products, fish, eggs and lean meats don’t just provide individual vitamins and minerals. They contain combinations of protein, fibre, healthy fats and thousands of biologically active compounds. You can’t necessarily reproduce all of that by swallowing a tablet.

Do multivitamins make us healthier?

Multivitamins are probably the most obvious place to start. The idea sounds perfectly logical: if vitamins are good for us, surely taking additional vitamins should make us healthier? Unfortunately, nutrition doesn’t always work like that. Research reviewed by the US National Institutes of Health suggests that multivitamin and mineral supplements have little or no effect on many major health outcomes, including cardiovascular disease. Evidence for preventing cancer and other chronic diseases is also inconsistent. In other words, taking a multivitamin isn’t the nutritional equivalent of an insurance policy against an unhealthy diet. If your diet already provides sufficient amounts of a nutrient, taking considerably more of it doesn’t necessarily provide an additional benefit.

There are, however, situations where supplementation makes much more sense.

Vitamin D – one supplement many people in the UK should consider Vitamin D is slightly different because relatively little comes from our diet. Much of our vitamin D is produced when sunlight hits our skin. And that presents an obvious problem in Britain. During autumn and winter, sunlight in the UK isn’t strong enough for most people to produce sufficient vitamin D. The NHS therefore recommends that adults consider taking 10 micrograms (400 IU) of vitamin D per day during autumn and winter. People at greater risk of deficiency may be advised to supplement throughout the year. Vitamin D is particularly important for maintaining healthy bones and muscles because it helps the body absorb calcium. So if there is one inexpensive supplement that has a particularly good case for widespread use in the UK, vitamin D is near the top of the list.

Protein supplements – useful, but not magical

Protein shakes are sometimes treated as though they contain some special muscle-building ingredient. They don’t. A whey protein shake is essentially a convenient source of dietary protein. You can obtain protein from chicken, fish, eggs, yoghurt, milk, beans, lentils, tofu and numerous other foods. If you can comfortably obtain enough protein through food, you don’t need protein powder. But protein supplements can be extremely convenient. This becomes particularly useful for people doing regular resistance training, older adults trying to maintain muscle mass, people dieting while trying to preserve muscle, and anyone who simply struggles to consume enough protein through normal meals.

A major meta-analysis published in the British Journal of Sports Medicine, involving 49 studies and 1,863 participants, found that protein supplementation enhanced increases in muscle size and strength during prolonged resistance training. However, benefits levelled off once total protein intake reached around 1.6 g per kilogram of body weight per day.

That’s an important point. More protein isn’t automatically better. The objective should be to consume enough protein – not as much as physically possible. And the resistance training itself remains the most important stimulus.

Creatine – probably the best-supported sports supplement

If you were going to single out one sports supplement with an unusually strong scientific evidence base, it would probably be creatine monohydrate. Creatine occurs naturally in the body and is also present in foods such as meat and fish. It helps rapidly regenerate ATP – the energy currency used by muscles during short, intense bouts of activity. Hundreds of studies have investigated creatine supplementation. The International Society of Sports Nutrition describes creatine monohydrate as one of the most effective nutritional supplements available for increasing high-intensity exercise capacity and lean body mass during training. For people performing resistance training, sprinting or other high-intensity exercise, creatine can therefore provide a genuine – although not miraculous – improvement.

Creatine may become even more interesting as we age

Maintaining muscle and strength becomes increasingly important as we get older. Loss of muscle mass and strength with ageing can eventually affect balance, independence, metabolic health and our ability to perform everyday activities. This makes the combination of resistance training, adequate protein and potentially creatine particularly interesting for middle-aged and older adults.

A 2017 meta-analysis of 22 studies involving 721 adults found that adding creatine to resistance training produced greater increases in lean tissue mass and upper- and lower-body strength than resistance training alone.

More recent research remains encouraging but also suggests we shouldn’t oversell the effect. A 2026 systematic review and meta-analysis found that creatine combined with resistance training produced a small but significant additional improvement in strength in healthy older adults, while the additional effects on muscle mass and physical function were less certain.

So creatine isn’t a replacement for lifting weights.

Think of it as a potentially useful addition to a good resistance-training programme. For most people using it for exercise, creatine monohydrate is the sensible choice. More expensive exotic versions haven’t convincingly demonstrated that they work better.

Omega-3 fish oil – perhaps not the miracle we once thought

Omega-3 supplements have long been promoted for cardiovascular health. Omega-3 fatty acids are certainly important nutrients, and oily fish such as salmon, sardines and mackerel are excellent foods. But taking fish-oil capsules doesn’t necessarily produce the same health benefits associated with eating fish. A large Cochrane review involving more than 160,000 participants found that increasing the long-chain omega-3 fats EPA and DHA had little or no effect on overall deaths or cardiovascular events, although there may be small benefits for some coronary outcomes and omega-3 supplementation can reduce triglyceride levels.

For most people, therefore, regularly eating oily fish is probably a better starting point than automatically reaching for fish-oil capsules.

What about vitamin B12?

Vitamin B12 is essential for healthy red blood cells and the nervous system. Most people who eat meat, fish, eggs or dairy products should be able to obtain sufficient B12 through their diet.

Vegans are different.

Vitamin B12 isn’t naturally present in meaningful amounts in most plant foods, so people following a vegan diet need reliable fortified foods and may require a B12 supplement. This is a good example of when supplementation isn’t about optimising an already adequate diet – it’s about preventing a genuine nutritional deficiency.

Iron – don’t supplement it “just in case”

Iron supplements are another good example of why more isn’t necessarily better. Iron is essential for making haemoglobin and transporting oxygen around the body, but taking additional iron when you don’t need it isn’t beneficial and high doses can cause side effects. Iron deficiency is more common in certain groups, particularly women experiencing heavy periods and people whose diets contain relatively little bioavailable iron. If blood tests identify iron-deficiency anaemia, iron supplementation is an established treatment. But routinely taking high-dose iron without knowing whether you’re deficient is a different matter.

If you’re persistently tired or suspect iron deficiency, getting it investigated is much more sensible than diagnosing yourself in the supplement aisle.

What about magnesium?

Magnesium seems to have become one of the fashionable supplements of recent years. It is involved in hundreds of processes within the body, including normal muscle and nerve function. But that doesn’t automatically mean taking extra magnesium improves those functions if you’re already consuming enough. Magnesium is widely available in foods including nuts, seeds, whole grains, legumes and green leafy vegetables. People who are deficient may obviously benefit from correcting that deficiency, but the idea that everyone who exercises needs additional magnesium isn’t supported simply because magnesium is involved in muscle function.

This principle applies to many supplements:

A nutrient being essential doesn’t mean taking extra is beneficial.

Water is essential too. That doesn’t mean drinking ten litres per day is healthier than drinking enough.

And what about collagen?

Collagen supplements have become enormously popular, particularly for joints, tendons and skin. There is some interesting research suggesting that collagen or gelatin combined with vitamin C and appropriate exercise loading may influence collagen synthesis, and some studies report improvements in joint symptoms. But the evidence isn’t nearly as established as it is for something like creatine.

Collagen is therefore better regarded as potentially useful rather than essential. If you’re recovering from a tendon or ligament injury, the most important factor remains an appropriate progressive rehabilitation programme. A scoop of collagen powder cannot compensate for inadequate rehabilitation.

Supplements that deserve more scepticism

At the other end of the spectrum are products where the marketing tends to run well ahead of the evidence. Fat burners, testosterone boosters, detox supplements and many expensive “superfood” or greens powders frequently fall into this category. That doesn’t mean every ingredient contained within them is useless. The problem is often that relatively ordinary nutrients are bundled together, given an impressive name and sold at a considerable premium.

If a supplement claims to “detox your body”, “melt belly fat”, “reset your metabolism” or produce dramatic muscle growth without meaningful changes to diet or exercise, your scepticism should increase roughly in proportion to the size of the claim.

Can supplements actually be harmful?

Yes. The assumption that something is safe simply because it is “natural” is incorrect. Some vitamins and minerals can be harmful in excessive amounts, while herbal supplements can interact with prescription medications. Iron is one example: excessive doses can cause gastrointestinal problems and very large doses can be dangerous. Supplements may also contain different doses or ingredients from those used in scientific research. This is particularly important for competitive athletes, who should choose products that have been independently tested for prohibited substances. If you’re taking prescription medication, have kidney or liver disease, are pregnant, or have another medical condition, it’s sensible to speak to your GP, pharmacist or registered dietitian before taking high-dose supplements.

So which supplements are actually worth considering?

For most healthy adults, the list is surprisingly short.

Vitamin D – particularly during the UK autumn and winter.

Protein powder – useful if it makes reaching an appropriate protein intake easier, particularly alongside resistance training.

Creatine monohydrate – one of the best-researched options for improving high-intensity exercise performance and potentially enhancing strength adaptations to resistance training.

Vitamin B12 – particularly important for vegans or people who have difficulty obtaining or absorbing sufficient B12.

Iron – when a deficiency has been identified rather than simply taken routinely.

Omega-3 – potentially useful in certain circumstances, although regularly eating oily fish remains an excellent option.

Other supplements may have particular applications, but whether they’re worthwhile depends on your diet, age, health, training and any genuine nutritional deficiencies.

Food first – supplements second

The supplement industry is extremely good at selling the idea that health comes in a tub or bottle.

Unfortunately, the things that have the greatest impact on our health are generally less exciting.

Eat plenty of fruit and vegetables.

Consume enough protein.

Include whole grains, nuts, seeds and other minimally processed foods.

Exercise regularly.

Perform resistance training.

Maintain a healthy body weight.

Sleep properly.

Don’t smoke.

Keep alcohol intake sensible.

Do those things consistently and you’ve already dealt with the big rocks.

Only then is it worth worrying about whether an additional supplement might provide the final few percent.

And that’s really the point.

Supplements can be useful. But they should supplement a healthy lifestyle – not attempt to replace one. And remember that all of our personal training plans include ongoing, practical help with eating and living healthier!

References and further reading

Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine. 2018;52:376–384.

Chilibeck PD, Kaviani M, Candow DG, Zello GA. Effect of creatine supplementation during resistance training on lean tissue mass and muscular strength in older adults: a meta-analysis. Open Access Journal of Sports Medicine. 2017.

Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition. 2017.

Cochrane. Omega-3 intake for cardiovascular disease. Systematic review of randomised controlled trials.

National Institutes of Health Office of Dietary Supplements. Multivitamin/mineral Supplements – Fact Sheet for Consumers.

NHS. Food for healthy bones – Vitamin D.

NHS. Vitamins and minerals – Vitamin B12.

NHS. Iron deficiency anaemia.