Severe single bouts of exercise and prolonged periods of heavy-duty training can increase the risk of illness in athletes. The mechanism underlying this has been hotly debated, with some scientists suggesting that the apparent immunosuppression associated with rugged exertion is linked with documented, training-induced decreases in levels of plasma glutamine. Blood concentrations of glutamine, an important substrate for cells of the immune system, can be increased by supplementing the diet with branched chain amino acids (BCAAs), but can such supplementation really reduce the risk of infection?
To find out, scientists recently worked with 12 elite male triathletes; average age of the athletes was 26, average weight was 74 kilograms ('The effect of branched chain amino acids supplementation upon the immune response of triathletes, Med Sci Sports Exerc, vol. 32 (7), pp. 1214-1219, 2000). Six of the athletes received six grams of branched chain amino acids twice a day for 30 days prior to the Olympic Triathlon, three grams 30 minutes before the triathlon (1.5 km of swimming, 40 km of biking, and 10 km of running), and then three grams per day for seven days after the race. The other six subjects received only a placebo.
As it turned out, plasma glutamine plummeted by 23% for the placebo takers after the race, while glutamine levels in the branched chain amino acids takers remained normal. Indicators of immune-system function were more positive for the branched chain amino acids supplementers after the triathlon, and - most importantly - the branched chain amino acids users had a lower incidence of infections during the overall study, compared with placebo athletes.
This study suggests that branched chain amino acids supplementation can reverse the reduction in plasma glutamine concentrations observed after prolonged intense exercise, improve immune responses during periods of strenuous exercise, and reduce the frequency of illness associated with hard training and competition. The investigation is marred somewhat, however, by the small sample sizes (just six athletes in each group), so athletes should wait for corroborative studies before jumping on the branched chain amino acids bandwagon.