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How Athletes Can Boost Immune Function to Stay Well

By Katie Davis | Feb. 18, 2014, 1:11 p.m. (ET)

fruitAs athletes ramp up their training, they put their bodies at a higher risk of illness and infection. Research indicates that athletes are at an increased risk of illness not only in the hours after a hard workout, but in the one to two weeks following a competition. This is likely due to the increase in stress hormones (particularly adrenaline and cortisol) associated with training and competition. However, there are things you can do to keep your immune system running strong and minimize your risk of illness during training and competition.

1. Eat well
Despite the fact that many athletes take multivitamins, antioxidant blends and the like, there is a lack of evidence to support high-dose supplementation of antioxidant vitamins, glutamine or echinacea to prevent exercise-associated immune system depression. In truth, there is much research about the positive synergistic effect of the vitamins and minerals consumed in food itself versus a supplement. At meals and snacks, focus on nutrient-rich foods and fluids to provide the immune system what it needs. A few examples include:
-Whole grain and fiber-rich cereals, breads and pastas, especially those that include flaxseed or chia seeds as ingredients
-Include a variety of whole fruits and vegetables throughout the day. Fruit is great as a snack on-the-go, at the office or at home. It is naturally portable and also a great source of fluid. Add veggies (frozen are great too) with every meal. The more color at meals the better.
-Don't settle for plain, boring sandwiches, soups or pastas. Fill them with color by adding fresh and dried fruit and fresh cut up vegetables. 

2. Eat enough of the right foods
Providing adequate fuel is a key step to keep your immune system running. What I see most often lacking in my athletes' diets is carbohydrate. Research indicates that athletes exercising in a carbohydrate-depleted state experience larger increases in circulating stress hormones than in the athlete who is well-fueled. Consuming adequate carbohydrate appears to limit the degree of exercise-induced immune system suppression during and after exercise. Studies suggest 30-60 grams of carbohydrate per hour of exercise to be adequate to prevent this suppression. Thirty grams of carbohydrate is equivalent to two cups of Gatorade, one whole medium-sized banana or a half cup dried fruit. 

3. Know your levels
It is important to have a blood draw every six months or so to know what is going on inside the body. When it comes to reducing risk of illness and infection, one important level to know is vitamin D. Research has linked vitamin D deficiency with an increase in infectious diseases. If a person is truly deficient, levels cannot be increased with food alone — instead high-dose supplementation must be utilized. Vitamin D deficiency is common in the winter months for those in the mid- to northern regions of the United States. So, ask your doctor to check your levels to determine if vitamin D supplementation is necessary.

4. Manage stress
A high level of stress causes a release of stress hormones in the body that can then wreak havoc on an already taxed immune system. Learn how to manage physical and psychological stress effectively before it gets out of hand. Not sure how? There is no shame in meeting with a great sports psychologist who can offer stress-reducing tactics to help you optimize your training and competition.

5. Sleep
It seems every month there is a new study on the beneficial effects of sleep — especially for athletes. Often overlooked, sleep is probably the most important thing you do in a 24-hour day. Aim for seven to nine hours daily of quality sleep. Turn off the TV and put away electronics early to allow your brain to "turn off" before getting into bed.

Katie Davis MS, RD, CSSD, LDN has a mission to help ordinary athletes become extraordinary competitors by using whole-food based nutrition to improve athletic performance. She is the owner of RDKate Sports Nutrition Consulting, based out of Naperville, Ill., where she offers expertise in sports nutrition, eating disorders/disordered eating, intuitive eating and weight management for sport. Katie holds a master’s degree in nutrition with an emphasis in exercise physiology. She is both a registered dietitian and one of only 550 RDs in the United States to be board-certified as a specialist in sports dietetics. As a runner, triathlete, snowboarder and rock climber, Katie understands the physical and mental challenges of being a top athlete. Katie has previously consulted with NCAA Division I & Division III, NFL and NBA athletes; she truly brings both her knowledge and experience to the table as sports dietitian. Katie is available for individual consulting, team talks and group seminars. Visit her website at; from there you can navigate to her weekly blog, Eat to Compete, and connect with her on Twitter or Facebook. Contact her directly at

The views expressed in this article are the opinion of the author and not necessarily the practices of USA Triathlon. Before starting any new diet or exercise program, you should check with your physician and/or coach.