Sports Supplements

The most useful way to think about supplements is to sort them by two things at once: how strong the evidence is that they work, and how safe they are to use. A widely used framework, developed by the Australian Institute of Sport, does exactly this and places supplements into four groups. The first holds products with good evidence of benefit when used correctly, and includes both performance supplements and practical sports foods and medical supplements. The second holds those with emerging but unproven evidence, worth watching but not yet established. The third holds the large number with little or no evidence behind their claims. The fourth holds substances that are banned or that carry a high risk of causing a failed drugs test, which should not be used.

The value of a framework like this is that it moves the conversation away from marketing and towards evidence and safety. For the clinician it gives a simple filter: is there real evidence for this product, is it safe, and does this particular athlete actually need it? Most supplements an athlete asks about fall into the lower groups.

Only a handful of performance supplements have earned strong evidence. Caffeine is one of the best established, improving endurance, alertness and reaction time. Creatine is another, supporting repeated high-intensity efforts, strength and power and the adaptations to training, with a good long-term safety record. Dietary nitrate, often taken as beetroot juice, can improve the efficiency of endurance exercise. Beta-alanine and sodium bicarbonate both work by buffering the acidity that builds up in hard exercise and may help efforts of the right intensity and duration, though bicarbonate commonly upsets the stomach. These are the products with a genuine physiological basis, and even then their benefit depends on the event, the individual and correct use.

Alongside these sit the sports foods, the drinks, gels, bars and protein powders that are convenient ways to meet nutritional needs around training rather than magic in themselves. A protein supplement, for instance, is a practical way to reach a protein target when whole food is not to hand, but it offers nothing that food cannot. The message is that these evidence-based options are the minority, that they supplement good nutrition rather than replace it, and that reaching for a supplement should follow, not precede, getting the basics right.

Distinct from performance supplements is the medical use of supplements to correct a genuine deficiency, which is where the SEM clinician and the wider musculoskeletal (MSK) team have a clear and evidence-based role. Iron deficiency is common, particularly in female athletes and endurance runners, and can cause fatigue and underperformance, but iron should be supplemented only when testing confirms a deficiency, since too much iron is harmful. Vitamin D deficiency is also common, especially in those who train indoors or live at northern latitudes through winter, and it matters directly to bone health, which links it to the recurrent bone stress injuries an MSK clinician sees. Calcium supports bone health alongside vitamin D and adequate energy intake.

The principle here is that these are treatments for a diagnosed problem, guided by history and blood tests, not blanket supplements for everyone. An athlete with fatigue, poor recovery or recurrent bone stress injuries deserves assessment for a deficiency, considered alongside energy availability, rather than an untargeted handful of pills. Correcting a real deficiency can make a genuine difference, which is precisely why it should be done properly.

The single most important safety point is that supplements are not tightly regulated, and some contain prohibited substances that are not on the label, whether through poor manufacturing or deliberate adulteration. For an athlete subject to anti-doping rules this is a serious hazard, because the principle of strict liability means the athlete is responsible for any prohibited substance found in their body, regardless of how it got there or whether they meant to take it. An inadvertent positive test from a contaminated supplement can end a career.

The risk cannot be removed entirely, but it can be reduced. Where a supplement is genuinely needed, athletes should choose products certified through a recognised batch-testing programme, keep a record of what they take, and check the current status of any substance through anti-doping resources. Weight-loss and pre-workout products carry particular risk and are best avoided.

In practice the clinician works through a simple sequence. Start by asking what the athlete already takes, since many take more than they realise. Address the foundations first, because good nutrition, sleep and training will outperform most supplements. Identify any genuine need, whether a diagnosed deficiency to correct or a specific, evidence-based performance aid for a particular event.

Where a supplement is warranted, steer the athlete towards evidence-based products from batch-tested sources, and make sure they understand contamination and strict liability. Involve a registered sports dietitian for anything beyond the straightforward, and check anti-doping status where relevant, keeping a record of the advice given. The overall stance is neither blanket enthusiasm nor blanket refusal, but a considered, safety-first approach that treats supplements as a small and carefully chosen part of a much bigger picture.

• •The Australian Institute of Sport supplement framework classifies supplements by evidence and safety and is a widely used practical reference.
• •International Olympic Committee (IOC) consensus statements on dietary supplements in high-performance sport inform current guidance on efficacy and risk.
• •UK Anti-Doping (UKAD) provides guidance on supplement risk, batch-testing and the principle of strict liability, and recognised programmes such as Informed Sport certify batch-tested products.
• •National Health Service and British Dietetic Association resources support advice on deficiencies and safe use, and a registered sports dietitian is the appropriate specialist.

• •Food first: a sound diet, good sleep and sensible training matter more than any supplement.
• •Frameworks such as the Australian Institute of Sport system sort supplements by strength of evidence and by safety.
• •Only a few performance supplements have strong evidence, including caffeine, creatine, dietary nitrate, beta-alanine and sodium bicarbonate.
• •Iron and vitamin D should be supplemented to correct a confirmed deficiency, not given untargeted, and both link to athlete health and bone.
• •Supplements are lightly regulated and may be contaminated with prohibited substances, and strict liability makes the athlete responsible.
• •Reduce risk by using batch-tested products, keeping records, and avoiding weight-loss and pre-workout supplements.