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The athlete immune system: 4 things nutrition can do to help keep it purring

If you’ve managed to avoid any sniffles or coughs this past winter, congratulations. Exposure to these little germies is a big piece of the illness puzzle, but your immune system certainly has to do its part once exposure takes place! But athletes are healthy and should have less concern, right?

We eat right, we workout – we’ve probably at some point fought the urge to vomit from exertion. So SURELY we can fight the flu.

But as an athlete you are still very much at risk to succumbing to illness, especially respiratory infections.  In fact, it is well-studied that folks regularly participating in prolonged (more than 90 minutes), intense bouts of activity are very susceptible to infections during intense training periods, tapers, and directly following competitions.

Turns out the more bad-ass we are on the course, field, or court (presumably from harder training efforts and all-out competition), the more attention we need to pay to keeping our immune system strong.

(In case it needs to be said – exercise is good for you! It goes without saying that in most cases it is good for health and immunity. But for folks training for marathons, Ironman races, century bike rides, multi-game tournaments, all-weekend swim meets, etc. it is another form of stress on the body.  We’ll talk stress below.)

Nutrition isn’t the only piece of the immune system puzzle, but there are certain things you can do with your nutrition to give yourself a fighting chance.

1. Keep the carbs for endurance-type exercise.  What do carbs have to do with immunity? Long, high intensity exercise increases stress hormones in the body, which in high or chronic amounts don’t do our immune system any favors. Some of these hormones (particularly cortisol) are moderated by maintaining blood sugar levels – so having adequate carbs helps minimize the rise in cortisol.

Carbohydrates also appear to help keep down certain cytokines or inflammatory markers, another immune system depressor.  So aim for adequate carbohydrate on a daily basis in addition to 30-60 grams of carbs per hour during workouts roughly 1.5 to 3 hours in length.

2. Build your bacteria.  The good kind.  Gotta hand it to the gut – not only does it perform all its regular gastrointestinal functions, but it is suspected that an alteration in good gut bacteria can be responsible for a dysfunctional immune system.  Although still requiring further research, there is some evidence indicating probiotics can be beneficial to the athlete’s ability to fight off upper respiratory tract infections.

There are countless types of good bacteria and probiotics  –Lactobacillus probiotics are most documented in athlete studies.  While a supplement could be used, try the food first – add one to two servings of yogurt or kefir to your daily regimen.  (Some people report tummy rumblings when using probiotics, but most see an improvement in things like gas, constipation, and diarrheaIf you are lactose intolerant start with small servings of kefir which is 99% lactose-free and see how you do.)

 3. Moderate your antioxidants.  So now we’re no longer waging war on free radicals and oxidation? Well not exactly. Antioxidants are still tremendously important, but there are a few reasons we want to find a happy middle ground.

First, research is inconclusive – which means some studies show benefits of high antioxidant supplementation for athlete immunity while others don’t.  The antioxidants typically researched for immune health these days are Vitamin C and E, quercetin and plant polyphenols (such as in grape juice and green tea).

 Second, remember that stress we talked about above?  Well some exercise stress is good – it involves the production of reactive oxygen species (ROS) which are actually beneficial at moderate levels for training adaptations (ie getting stronger and faster).  It’s suspected that high antioxidant intake could interfere with this process and more research is necessary before supplementation can be recommended.

 So the bottom line is to continue to consume a diet with plenty of fruits and vegetables, but think twice before adding high doses of antioxidant supplements.

 4. Meet your energy needs.  Finally, one of the simplest ways to help keep your immune system strong is to ensure you are consuming enough calories to meet both your training and daily life needs.  A diet low in calories and protein is a sure-fire way to suppress immunity.

Although the typical flu season may have passed, athletes involved in intense training can still be at risk for respiratory (and other) infections without taking the proper lifestyle precautions, including these nutrition recommendations.  It’s never too early (or late) to put these practices in place.


Burke L, Deakin V. Clinical Sports Nutrition. 4th Edition. North Ryde, Australia. McGraw-Hill Australia Pty Ltd. 2010.

Cox AJ, Pyne DB, Saunders PU, Fricker PA. Oral administration of the probiotic Lactobacillus fermentum VRI-003 and mucosal immunity in endurance athletes. Br J Sports Med.2010; 44(4): 222-226.

Lamprecht M, Frauwallner A. Exercise, intestinal dysfunction and probiotic supplementation. Med Sport Sci.2012; 59: 47-56.

Maughan R, Gleeson M. The Biochemical Basis of Sports Performance. 2nd Edition. New York. Oxford University Press. 2010.

Sureda A, Ferrer MD Mestre A, et al. Prevention of neutrophil protein oxidation with vitamin C and E diet supplementation without affecting the adaptive response to exercise. Int J Sport Nutr Exerc Metab. 2013; 23: 31-39.

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