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After last week’s post on Immune System and Elite Swimmers, one of our readers posted an excellent question:

I understand that this gives you ideas of how to spot the likelihood of the upper respiratory infections, but what suggestions exist for minimizing or eliminating them? Is there a dietary or vitamin plan?

First things first: Many illnesses are within our control even if they seem like random luck.  Yes, there are cases in which you do everything right and you turn up with a cold at the wrong time, just as there are other outliers who take poor care of their bodies but avoid immune system setbacks.  But if you challenge the organism when it’s in a depressed state (regardless of WHY it’s in that state), the body is more vulnerable to immune system setbacks .  Revisit what you are doing in the water; otherwise special meal plans and supplements are just figurative band-aids for immunity problems caused by ineffective training and deficient diets. 

Monitoring is also important.  Several weeks ago we addressed ways to assess autonomic nervous system readiness.  We don’t know if the body is vulnerable unless we actually check its state daily.  If you don’t assess, it’s just a guess!    

Building the immune system is like a cyclist learning to handle a bike.  You always wear a helmet on the bike, but you must learn to learn how to avoid crashes and not need your helmet.  Search for any deficiencies first before choosing supplementation or modifying diet beyond normal athlete recommendations.  Once we establish that our training is not causing any more stress than necessary for adaption, we can explore ways to fortify the immune system.  But as with training, it’s most important to identify deficits first.  
“Ensuring adequate energy, carbohydrate and protein intake and avoiding deficiencies of micronutrients are key to maintaining immune health.” (Walls 2011)

In one recent study, Mestre-Alfaro (2011) studied the effect of phytoestrogen supplementation in female swimmers.  A control group received a supplement with vitamins C and E, while the experimental group received the same beverage but also with phytoestrogens.  The experimental group had significant improvements in enzyme activity for lymphocytes and erythrocytes after exercise, indicating improved immune response.  Phytoestrogens are not female-specific but can be obtained naturally through legumes, whole grain cereals, flax, various seeds, and even bourbon, among several other sources.

Although not swim specific, Walsh (2011) notes that nutritional supplements including flavonoids such as quercetin and Lactobacillus probiotics can augment some aspects of immune function and reduce illness rates in exercise-stressed athletes Quercerin-rich foods include: Black and green teas, apples, onions, red grapes, leafy green vegetables, and several berry types.  Lactobacilus probiotic food sources include yogurt, dark chocolate, pickles, miso soup, and tempeh.  Walsh (2011) also notes that “Limited data are non-supportive or mixed for use of N-3 polyunsaturated fatty acids, beta-glucans, bovine colostrums, ginseng, echinacea or megadoses of vitamin C by athletes.” 

Vitamin C is commonly recommended for immunity, but as noted, the evidence on vitamin C and the immune system is mixed.  In swimming, Constantini (2011) studied the effect of vitamin C on upper respiratory tract infections in male and female adolescent swimmers but found that only males improved immunity.  However, authors specificalluy called for additional study to confirm or deny these conclusions. 

Interestingly, vitamin C may indirectly affect immunity as it is often linked to iron absorption.  Healthy iron levels can help swimmers absorb their training loads, making them less vulnerable to overtraining.  Although vitamin C has received mixed reviews in the literature, supplements combining vitamin C with other vitamins such as vitamin E have been shown to improve immunity in athlete populations (Tauler 2002, Sureda 2008)

Minerals also play a key role in immunity: Dragan (1990) studied thirty three top level male and female swimmers and found that selenium supplementation improved blood markers for immunity.  Brazil nuts, oysters, fish, and sunflower seeds are among the top sources for selenium.
Ensure your swimmers are training appropriately and meeting basic nutrition needs before worrying about supplementation.  Nevertheless, know that robust evidence supports adding flavonoids, phytoestrogens, and selenium to the diet specifically to improve immunity among athletes.

  1. Constantini NWDubnov-Raz GEyal BBBerry EMCohen AHHemilä H.  The effect of vitamin C on upper respiratory infections in adolescent swimmers: a randomized trial.  Eur J Pediatr. 2011 Jan;170(1):59-63. Epub 2010 Aug 6.
  2. Walsh NPGleeson MPyne DBNieman DCDhabhar FSShephard RJOliver SJBermon SKajeniene A.  Position statement. Part two: Maintaining immune health.  Exerc Immunol Rev. 2011;17:64-103.
  3. Drăgan IDinu VMohora MCristea EPloeşteanu EStroescu V.  Studies regarding the antioxidant effects of selenium on top swimmers.  Rev Roum Physiol. 1990 Jan-Mar;27(1):15-20.
  4. Tauler PAguiló AFuentespina ETur JAPons A. Diet supplementation with vitamin E, vitamin C and beta-carotene cocktail enhances basal neutrophil antioxidant enzymes in athletes.  Pflugers Arch. 2002 Mar;443(5-6):791-7.
  5. Sureda ATauler PAguiló ACases NLlompart ITur JAPons A.  Influence of an antioxidant vitamin-enriched drink on pre- and post-exercise lymphocyte antioxidantsystem.  Ann Nutr Metab. 2008;52(3):233-40. Epub 2008 Jun 19.
  6. Mestre-Alfaro AFerrer MDSureda ATauler PMartínez EBibiloni MMMicol VTur JAPons A.  Phytoestrogens enhance antioxidant enzymes after swimming exercise and modulate sex hormoneplasma levels in female swimmers.  Eur J Appl Physiol. 2011 Sep;111(9):2281-94. Epub 2011 Feb 18.
By Allan Phillips. Allan and his wife Katherine are heavily involved in the strength and conditioning community, for more information refer to Pike Athletics.


Dr. John Mullen, DPT, CSCS world-renowned physical therapist and strength coach.
  1. October 1, 2012

    Great follow up and thank you for answering my question. My family has always “relied” heavily on Vitamin C and I always had my doubts. The proof that it indirectly increases immunity via increased iron absorption is great to know. Thank you again!

  2. October 2, 2012

    I am a strong proponent of Garlic capsules. You can get the odorless kind, and they not only help with those who have blood pressure issues, but I swear, I have not had a single cold in the two years I have been taking them. And I work in urgent care.

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