While moderate physical activity can bolster immune function, strenuous exercise or intense physical training can actually suppress the immune system. In a piece for the Huffington Post, Leo Galland, M.D., the director of the Foundation for Integrated Medicine, noted the physical stress on the body can adversely affect immunity. However, researchers are finding certain nutritional ingredients may help athletes stay healthy and avoid immune depression.
Galland particularly focused on amino acids, the building blocks of protein. He noted Japanese researchers recently reported cysteine (700 mg/d) and theanine (280 mg/d) could restore the activity of natural killer (NK) cells, which had been suppressed by intense training; the same combination of aminos also reduced inflammatory markers, maintained immune function and reduced infection rates in distance runners.
The amino acid citrulline (6 g) was found to preserve immune function in cyclists, helping the body preserve the activity of certain white blood cells. Similarly, French researchers found when untrained athletes took citrulline after exercise, they avoided post-exercise fatigue and muscle soreness.
Galland also advised readers to stay hydrated, as much for the mental benefits as the physical ones. He cited a Tufts University study that found dehydration adversely affected mood and cognitive function—specifically attention—in young athletes.