Vitamin B₂

Vitamin B₂ (riboflavin) is involved in energy production and normal cellular function through its coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). These coenzymes are mainly involved in obtaining energy from consumed carbohydrate, protein, and fat. Food sources of riboflavin include dairy products (e.g., milk, yogurt, cottage cheese), dark green leafy vegetables (e.g., spinach, chard, mustard greens, broccoli, green peppers), whole grain foods, and enriched grain foods.

No studies suggest that riboflavin-deficiency symptoms are common in athletes. Also, no apparent toxicity symptoms occur from consuming more than the DRI. Several studies have suggested that athletes may have higher requirements than the DRI, which is based on approximately .6 milligrams per 1,000 calories. In a series of studies performed on exercising women and women seeking to lose weight, the riboflavin requirement was found to range between .63 and 1.40 milligrams per 1,000 calories. ^2-4

There is some evidence that physical activity increases the requirement to a level slightly higher than .5 milligrams per 1,000 calories, but not more than 1.6 milligrams per 1,000 calories.⁵ However, even with this apparently higher requirement for athletes, no studies clearly demonstrate an improvement in athletic performance with intakes greater than the RDA. Since low-dose supplements of this vitamin induce no apparent toxicity symptoms, athletes could take a supplement delivering 1.6 to 3.0 milligrams of riboflavin as part of a B-complex supplement. This level of intake would serve as an adequate preventative measure to help the athlete avoid the symptoms-headache, nausea, weakness-associated with extremely high doses (more than 100 times the RDA).⁶