Nutrient Supplementation

Athletes who fail to consume sufficient carbohydrate or enough total energy are likely to be at increased risk of inadequate vitamin C, thiamin, riboflavin, niacin, calcium, magnesium, and iron intakes.¹⁸ A study of marathon runners found that supplement usage (especially vitamins C and E, calcium, and zinc) was common. Forty-eight percent of the runners questioned reported using at least one supplement within the 3-day period surrounding the Los Angeles Marathon.¹⁹ Other studies confirm that nonsupplemented marathon runners, soccer players, wrestlers, and basketball players have adequate serum concentrations of vitamin C and vitamin B₆, so supplementation of these vitamins does not appear to be warranted.^20,21 In a study evaluating the effectiveness of magnesium supplementation on marathon runners, the supplementation did not improve resistance to muscle damage during the race, did not enhance muscle recovery after the race, and did not improve running performance.²²

Male marathon runners were evaluated to determine if the consumption of a commercial ergogenic aid supplement containing vitamins, minerals, amino acids, and unsaturated fatty acids was useful in improving performance. Results indicate that the ergogenic aid had no effect on oxygen consumption or any other important metabolic or physiological parameter that might be useful to endurance athletes.²³