Immunity Declared

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Winter – that time of the year again when people are more likely to catch colds and infections. An upper respiratory tract infection (URTI), although trivial, is undesirable to runners as it impairs training time, training volume and intensity.

We know from research that periods of hard training with limited recovery and/or inadequate energy intake AND prolonged bouts of strenuous exercise (>90 minutes), (especially without carbohydrate intake) or participation in ultra-endurance events depresses immune function. This depression in immune function can last up to 72 hours and is typically known as the “open window period”. During this period runners are at increased risk of picking up minor illnesses and infections, most commonly URTI.

The jury is still out to find clear evidence on some claimed immune-boosting supplements, which will be discussed in the follow-up article. There are however enough evidence to show that the following nutritional strategies may work to enhance immunity.

Carbohydrates
When blood glucose levels fall during exercise, stress hormones rise and this can impair immune function. In studies where carbohydrates were consumed during longer runs or taken in high amounts before the start of prolonged runs, results have shown smaller immune dysfunction post event (compared to those who were carbohydrate deprived).

Therefore when running for more than 90 minutes it is recommended to consume 30-60g carbohydrates per hour. Recovery is also important.  (Check out Recovery Nutrition)

Probiotics
Probiotics are live microorganisms that protects the gut. In athletes it has been found in some studies that daily probiotic ingestion resulted in fewer days of respiratory illness and lower severity of URTI symptoms. Probiotics also improve gut immunity and speed recovery from diarrhea.

Zinc & Iron
A deficiency in either zinc or iron can compromise immunity, although taken in excess, both these minerals are toxic and can ALSO impair immune function. It is therefore important for runners to include foods that are high in zinc and/or iron in their daily diets.

Some studies show evidence that zinc syrup, tablets or lozenges may lessen the severity and duration of the common cold. Sensible advice is therefore to only take zinc supplementation at the onset of cold symptoms to speed recovery. Chronic zinc supplementation is not recommended and a healthy balanced diet should help to maintain normal levels of zinc and iron.

Remember that more is not always better… Only when you are deficient in a certain nutrient will supplementation really help. Taking more than what is needed is not always better and can in fact be detrimental.