Periods of heavy training are sometimes associated with depressed immune function, and compromised immune function can be further aggravated by inadequate nutrition. Combining training with school or work can overtax your resources, stress your body, and compromise your ability to fight infection. A strong immune system should result in fewer colds and other viruses, and when you do get sick, should enable you to make a quicker recovery.
Specific foods can strengthen your immune system and help to prevent unwanted halts in your training program due to illness. Vitamin C has a widespread reputation as an immune system booster, but it is not a magic pill for preventing the common cold. It should, however, be part of your daily diet in adequate amounts. Though a daily multivitamin-and-mineral supplement may contain the Daily Value (DV) of vitamin C, don’t underestimate the importance of ample food sources of this nutrient. Athletes can consume more than three servings of fresh fruit and up to 2 cups of cooked vegetables daily for ample amounts of dietary vitamin C. Megadoses of vitamin C in supplement form have not been shown to protect the immune system—250 milligrams is adequate to saturate body stores.
Fruits and vegetables contain hundreds of phytochemicals that provide many preventive health benefits and are also excellent sources of carotenoids that boost the activity of the white blood cells called lymphocytes. Beta-carotene can also be converted to vitamin A, an important nutrient for the immune system. Other nutrients important for a strong immune system are zinc, iron, and vitamins B6 and B12. A good daily multivitamin and mineral supplement providing 100 percent of the DVs ensures adequate nutrient intake. Megadosing with vitamins and minerals can compromise the immune system, and excessive intakes of iron, zinc, and vitamin E are not advised. A balanced diet that includes a large variety of foods provides many nutrients that work together to keep your immune system healthy, and a moderate-dose supplement ensures that you are obtaining all the nutrients that you need.
Consuming adequate calories is beneficial not only for an athlete’s recovery and energy levels but also for maintaining a healthy immune system. Falling short of your calorie requirements can compromise your immune system, as can poorly planned and low-calorie diets, especially those low in protein. Diets too low in calories can result in inadequate intake of vitamins and minerals, which also decreases immunity. Training with optimal stores of glycogen obtained from a diet adequate in calories and carbohydrates not only provides fuel for your workouts but also boosts your immune system.
Levels of certain stress hormones normally rise during exercise, but athletes who train in a carbohydrate-depleted state experience a greater increase in these hormones than those who are well fueled. Your immune system appears to function best when carbohydrate is available. Consuming carbohydrates during exercise also seems to diminish some of the immunosuppressive effects of intense training. Generally, strenuous exercise suppresses immune function and gives viruses a strong “window of opportunity” after a workout to gain a foothold in your body and start an infection. Besides replacing carbohydrate during training, practice optimal recovery nutrition guidelines as well.
New research is also looking at the effect of probiotics/prebiotics and vitamin D in the immune system of athletes during periods of heavy training.
Sports Nutrition for Endurance Athletes shows runners, cyclists, and triathletes how to address specific nutritional needs for short- and long-course racing and busts dozens of myths and misconceptions along the way.