Does vitamin and mineral supplements improve measures of performance in people consuming adequate diets?
In the first place, DRI Tables, developed by the Institute of Medicine’s Food and Nutrition Board:
- Dietary Reference Intakes: RDA and AI for Vitamins and Elements
- Dietary Reference Intakes: UL for Vitamins and Elements
American College of Sports Medicine current comment "Vitamin and Mineral Supplements and Exercise"
Physical activity may increase the need for some vitamins and minerals. However, the increased requirement generally can be attained by consuming a balanced diet based on a variety of foods.
Although vitamin and mineral supplementation may improve the nutritional status of an individual who consumes marginal amounts of nutrients and may enhance the physical performance of those athletes with overt nutrient deficiencies, there is no scientific evidence to support the general use of vitamin and mineral supplements to improve athletic performance. The increased energy intake of physically active individuals should provide the additional vitamins and minerals needed if a wide variety of foods is included in the diet.
Estimates of nutrient requirements for physically active people are based on population standards.
Commonly used estimates are the recommended daily allowance (RDA) and the estimated safe and adequate daily dietary intake (ESADDI). These estimates are calculated to meet the needs of nearly all members of the U.S. population, with the exception of pregnant women and people with medical problems. Although population standards, such as RDA and ESADDI, were not derived for individuals participating in strenuous physical activity, they provide a reasonable approximation of the vitamin and mineral needs of physically active people.
Although research has demonstrated that specific vitamins may possess some health benefit (e.g., Vitamin E, niacin, folic acid, vitamin C, etc), few have been reported to directly provide ergogenic value for athletes. However, some vitamins may help athletes tolerate training to a greater degree by reducing oxidative damage (Vitamin E, C) and/or help to maintain a healthy immune system during heavy training (Vitamin C). Theoretically, this may help athletes tolerate heavy training leading to improved performance. The remaining vitamins reviewed appear to have little ergogenic value for athletes who consume a normal, nutrient dense diet.
Suggestions that there is no benefit of vitamin supplementation for athletes and/or it is unethical for an sports nutrition specialist to recommend that their clients take a one-a-day multi-vitamin and/or suggest taking other vitamins that may raise HDL cholesterol levels and decrease risk of heart disease (niacin), serve as antioxidants (Vitamin E), preserve musculoskeletal function and skeletal mass (vitamin D), or may help maintain a health immune system (Vitamin C) is not consistent with current available literature.
For example, calcium supplementation in athletes susceptible to premature osteoporosis may help maintain bone mass. There is also recent evidence that dietary calcium may help manage body composition. Iron supplementation in athletes prone to iron deficiencies and/or anaemia has been reported to improve exercise capacity. Sodium phosphate loading has been reported to increase maximal oxygen uptake, anaerobic threshold, and improve endurance exercise capacity by 8 to 10%. Increasing dietary availability of salt (sodium chloride) during the initial days of exercise training in the heat has been reported to help maintain fluid balance and prevent dehydration.
Finally, zinc supplementation during training has been reported to decrease exercise-induced changes in immune function. Consequently, somewhat in contrast to vitamins, there appear to be several minerals that may enhance exercise capacity and/or training adaptations for athletes under certain conditions.
Suggestions that there is no benefit of mineral supplementation for athletes and/or it is unethical for a sports nutrition specialist to recommend that their clients take minerals for health and/or performance benefit is not consistent with current available literature.
Proposed nutritional ergogenic aids – vitamins & minerals
RDA – Males 120 mcg/d, Females 90 mcg/d
Vitamin K supplementation (10 mg/d) in elite female athletes has been reported to increase calcium-binding capacity of osteocalcin and promoted a 15-20% increase in bone formation markers and a 20-25% decrease in bone resorption markers suggesting an improved balance between bone formation and resorption.
RDA – Males 16 mg/d, Females 14 mg/d
Studies indicate that niacin supplementation (100-500 mg/d) can help decrease blood lipid levels and increase homocysteine levels in hypercholesteremic patients. However, niacin supplementation (280 mg) during exercise has been reported to decrease exercise capacity by blunting the mobilization of fatty acids.
RDA – Males 90 mg/d, Females 75 mg/d
There is some evidence that vitamin C supplementation (e.g., 500 mg/d) following intense exercise may decrease the incidence of upper respiratory tract infections.
Phosphorus (phosphate salts)
RDA – 700 mg/d
Recent well-controlled research studies reported that sodium phosphate supplementation (4 g/d for 3 d) improved the oxygen energy system in endurance tasks. There appears to be little ergogenic value of other forms of phosphate (i.e., calcium phosphate, potassium phosphate). More research is needed to determine the mechanism for improvement.
Males 11 mg/d Females 8 mg/d
Studies indicate that zinc supplementation (25 mg/d) during training minimized exercise-induced changes in immune function.
Some recomendations from Lyle McDonald
RDA – 15 mcg/d
It also looks like maintaining adequate Vitamin D status may be a key to optimal athletic performance although direct research is lacking. Unfortunately, determining serum levels of Vitamin D intake to determine optimal levels of supplementation requires blood work. Athlete with access to testing should strive for levels of 50 ng/ml or higher. It requires 100 IU’s of Vitamin D to raise serum levels by 1 ng/ml and athletes with access to blood testing can determine their daily dose that way (e.g. to raise levels from 30ng/ml to 50 ng/ml would require 2000 IU’s per day).
Failing that, a daily supplementation level of 2000 IU’s should be safe and reasonable for most. Blood work is still preferred and this is another place where mega-dosing (greater than perhaps 10,000 IU’s per day) can be problematic. More isn’t better.
- Nutrition. 2004 Jul-Aug;20(7-8):632-44. – Vitamin and Mineral Status: Effects on Physical Performance