Vitamins and minerals for people who train: when supplementing makes sense
The principle
The IOC consensus separates correcting a deficiency from taking a supplement "just in case". A deficiency, even mild, can reduce training and performance, but it is hard to measure: for many nutrients there is no single threshold of "adequate". When status is low, a supplement can be part of treatment, together with a plan that is adequate in energy and nutrients.1 That is why there are no doses here: they depend on tests and on the person, and the assessment belongs to a doctor or sports dietitian.
Nutrients, one by one
- Vitamin D: many athletes are at risk of insufficiency at various times of year. There is no consensus on the value that defines deficiency or sufficiency, and the need to supplement depends on sun exposure and skin type. Guidelines for athletes are not established; high doses need monitoring to avoid toxicity. In its efficacy table the IOC gives moderate support to supplementing from autumn to spring to maintain status, and says more studies are needed.1 The AIS lists vitamin D, iron, calcium, folate and zinc in Group A: for identified athletes with protocols, not for general use.2
- Iron: low status can come from poor intake or absorption, too little energy, menstruation, red-cell breakdown from foot strike, losses in sweat or altitude training. It needs several measures together (for example ferritin, transferrin saturation, haemoglobin). High-dose iron should not be taken unless there is a deficiency, and a deficiency needs clinical follow-up.1
- Calcium: risk rises with avoiding dairy and other calcium-rich foods, with restricted energy and with disordered eating. There is no good indicator of calcium status; vitamin D and bone health also matter.1
- Vitamin B12, folate, iodine: the IOC says that for B12 (vegan or near-vegan diet), folate (women who might become pregnant) and iodine (low-iodine areas, no iodised salt) supplementing may be warranted, but these apply to the general population, not specifically to athletes.1
- Vitamins C and E: high doses of single antioxidants may blunt training-induced adaptations. For vitamin C in periods of heavy exertion, a Cochrane review cited by the IOC, of 5 studies (598 people), shows about 50% fewer respiratory symptoms; no benefit if started after symptoms appear. It is unclear whether it blunts adaptation in very well-trained athletes.1
Before buying anything
- Start with food and training load: too little energy intake is a cause of deficiency that no supplement fixes.
- Suspect a deficiency? Tests and a doctor, not self-diagnosis. Too much iron or vitamin D carries risks.
- We do not cover multivitamins: the sources read give no picture for performance.
- Anti-doping and contamination: the WADA list changes every year and an unchecked product can contain banned substances.31 WOLF LAB does not certify products or batches and does not recommend brands.
How we reviewed it
Document review: text of the 2018 IOC consensus (tables on vitamin D, iron, calcium, vitamin C) and the AIS Group A page. Primary studies not read. No WOLF LAB tests.
Limits. 2018 consensus sources, not primary studies: nothing more recent read. No dose given. Multivitamins, zinc, magnesium, omega-3 not covered. Deficiency thresholds are not unique. Not medical advice.
Sources
- Maughan RJ et al. IOC consensus statement: dietary supplements and the high-performance athlete. British Journal of Sports Medicine, 2018. PMC.
- AIS (Australian Sports Commission). Sports supplements, Group A. AIS.
- WADA. The Prohibited List. WADA.
Sources read on 31 October 2026: the IOC consensus text and AIS pages, not primary studies. General information, not medical advice. No WOLF LAB tests.