The use of nutritional supplements by athletes for the purpose of improving performance is common. Commercial promotion of nutritional supplements claims a variety of performance-enhancing results. Typically, nutritional supplements have 100 percent to 500 percent of the daily recommended intake. While the use of supplements is recommended for athletes with calorie restriction in weight-control sports, vegans, or those who consume a diet excessive in highly processed carbohydrates, most competitive athletes take a multivitamin, even if they do not fit these criteria.
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Athletes and Nutritional Supplements
In a report on vitamin and mineral supplement use among 311 university athletes, more than half reported to use nutritional supplements. This report, published in the December 1999 issue of the "International Journal of Sports Nutrition and Exercise Metabolism," found males were more likely than females to report "too expensive" as the reason for not taking supplements. The most common supplement was multivitamins plus minerals. Females were more likely to take calcium and iron, and males vitamins B-12 and A.
B-12 and Athletes
Athletes have used vitamin B-12 supplements for a number of years. It is common for athletes to be injected with large amounts of vitamin B12 -- often 1 g injections -- before competitions to improve performance and endurance. However, research published in the July 2004 issue of "Nutrition" showed that supplementing B-12 has no affect on athletic performance in the absence of nutritional deficit.
In another frequently cited study, published in the June 1992 issue of the "International Journal of Sports Nutrition," researchers explored the impact of athletes using doses up to 10 to 50 times the recommended daily intake of a B complex vitamin, and vitamins A and C for up to eight months. This research was based on the assumption that intense exercise and training might increase the requirements of these vitamins and was looking for improvements mostly in aerobic performance, but none was found.
Vegetarian athletes are at risk for developing vitamin B-12 deficiency because natural food sources of vitamin B-12 are limited to animal foods. Therefore, vegetarian athletes might benefit from vitamin B-12 supplementation. In addition, fortified breakfast cereals can be used as a dietary source of vitamin B-12 for strict vegetarians and vegans. Before taking any nutritional supplements, consult your doctor.