Immune Function, Exercise and the Importance of Nutrition

By Kary Woodruff

Winter is a prime season for colds, the flu, and other respiratory illnesses. While regular exercise is associated with improved health, a rigorous training plan along with other daily stressors may be reducing your immune function, making you more susceptible to getting sick.

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With your next competition just months away, the last thing you need is a cold to prevent you from sticking to your training plan. Therefore, it is important to consider the factors affecting your immune function. These include:

 - Repeated bouts of heavy physical exertion (high intensity intervals, for example)
 - Lack of sleep
 - Severe mental stress
 - Poor nutrition habits
 - Exposure to illness
 - Poor hygiene (i.e. hand-washing)

Planning ahead is key to managing these factors so that your immune system stays strong, even during your hardest training periods. This is especially true of nutrition. Good eating habits are an essential component of your training program. Because the training load for each person varies, it is important to design a meal plan that includes essential vitamins and minerals, as well as the right amount of calories. Avoiding restrictive eating patterns and fad diets will also help ensure a good intake of important nutrients. 

What about nutritional supplements?

Research suggests many athletes use nutritional supplements claiming to boost immune function. These supplements include antioxidant vitamins (vitamin C and E), glutamine, zinc, and Echinacea extracts. While much research has been done on nutritional supplements and immune function, there is little evidence to support that high doses of these supplements prevent immune suppression and protect you from illness.1 Though research on zinc suggests that oral zinc treatment may reduce the length of symptoms of the common cold, we are still waiting on larger, comprehensive studies before we recommend zinc supplementation.2 Bottom line – eating a varied diet that is nutrient rich and energy sufficient is a better approach to maintaining your health than relying on nutritional supplements. Specifically, eating lots of fruits and vegetables, whole grains, and lean proteins will give you the variety of vitamins and minerals that you need.  Good nutrition habits, managing your stress, sleep habits, exercise and daily activity loads, and exposure to illness will minimize your risk of infection and keep you training hard during the winter months. 


References
1. Gleeson M, Nieman D, Pedersen BK. Exercise, nutrition and immune function. Journal of Sports Sciences. 2004:22;115-25.
2. Science M, Johnstone J, Roth DE, Guyatt G, Loeb M. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. 2012:184(10);551-561.