Judging supplements: evidence before the label
Supplements are not medicines and are regulated differently. Food comes first; only a few ingredients with a clear gap or supporting evidence are worth considering. Do not try one for the first time on race day, and do not treat a testing mark as proof of effect.
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Supplements are not medicines
The U.S. FDA regulates dietary supplements differently from prescription drugs. Products do not need pre-market approval for efficacy and safety in the way drugs do; companies are responsible for labelling and safety, and the FDA mainly acts after products reach the market. Being available does not mean proven effective or safe for everyone.
A supplement label may list ingredients without full doses or third-party testing information, and actual content can differ between batches. Choosing products with third-party testing and transparent ingredients and doses reduces some risk, but does not guarantee benefit.
Ask what is missing first
For most runners, a balanced diet supplies most of what training needs. Whether protein, carbohydrate, iron, vitamin D or anything else needs supplementing depends on diet, testing, health and training load, not on “runners should take it”. Without a clear deficiency or professional advice, stacking supplements usually adds little benefit while increasing cost and interaction risk.
The ISSN protein position stand supports reasonable protein distribution when total protein and energy are adequate; that is not proof that everyone needs protein powder. Caffeine has moderate-to-large effects in some endurance settings, but dose, sleep and anxiety limits apply; see the caffeine article.
Levels of evidence
Randomised trials, systematic reviews and meta-analyses are more reliable than a single small study. Supplement research often has small samples, funding issues and differences in dose and population. When a product claims a percentage improvement, ask who was studied, what the comparison was, whether the difference matters and whether it has been replicated. Cell and animal studies, or an “expert recommendation”, do not directly prove benefit for runners.
Be especially cautious of products claiming to treat disease, replace medication or guarantee performance. Supplements do not replace medical diagnosis, treatment or a balanced diet. With a medical condition, pregnancy, breastfeeding, medication or a history of disordered eating, consult a doctor or registered dietitian first.
Racing and anti-doping
Do not try a new supplement for the first time on race day. Some ingredients may be restricted by anti-doping rules or contaminated during manufacture; being sold in a normal shop does not make it permitted in competition. Check the latest prohibited list from the event and anti-doping authority, and keep batch and purchase records.
Scope and limits
This page does not recommend a brand, dose or stack, or decide whether a product suits you. Supplements can interact with medication and burden the liver, kidneys, cardiovascular system or gut; stop and seek medical advice for unusual symptoms.
Sources and scope
Supplement regulation follows the FDA dietary-supplements page; protein principles follow the ISSN protein and exercise position stand; caffeine effects and limits follow the ISSN caffeine position stand. This is general information, not individual nutrition or medical advice. Checked 2026-10-28.
Sources and evidence
Dietary supplements are regulated differently from conventional foods and drug products. Manufacturers and distributors are responsible for evaluating the safety and labeling of their supplements before marketing. The FDA can take action against adulterated or misbranded supplement products after they reach the market.
An overall daily protein intake of 1.4-2.0 g/kg body weight per day is sufficient for most exercising individuals. General per-serving recommendations are about 0.25 g of high-quality protein per kg body weight, or an absolute dose of 20-40 g, distributed every 3-4 hours across the day. Physically active people can meet protein needs with whole foods, while supplements can be a practical way to ensure adequate intake. Endurance athletes should focus on adequate carbohydrate intake for performance; protein may help offset muscle damage and support recovery.
Caffeine can acutely enhance various aspects of exercise performance in many but not all studies, with aerobic endurance showing the most consistent moderate-to-large benefits. Doses of 3-6 mg/kg body mass have consistently improved exercise performance; very high doses are associated with more side effects. A common timing is about 60 minutes before exercise, although optimal timing depends on the caffeine source. Individual responses vary, and caffeine can adversely affect sleep or anxiety in some people.
Version and checks
Written by: RunMap Editorial
Updated: 28 Oct 2026
Checked: 28 Oct 2026
This article provides general running information and is not a medical, nutrition or training prescription. For persistent pain, illness or extreme conditions, seek a qualified professional or local emergency care. Legal & licences