Why do more people get sick in the winter than any other time of the year? The answer is relatively simple-more people tend to spend more time inside warm enclosed places with other potential germ-spreading people. Germs and viruses thrive in warmer conditions making the inside environment a breeding ground for contagious diseases. If you are an athlete, runner or avid exerciser, you are even more susceptible to possible infection - specifically an upper respiratory tract infection (URTI). With winter around the corner, this article provides some simple steps that can be taken to help exercisers stay healthy and train harder this season.

Why is immunity lowered in runners and aerobic exercisers?

Exercise in all its forms is considered a stress by the body, and as a result hormones such as cortisol and adrenaline are released to help adapt to the stress. Cortisol is released from the adrenal gland and although its main purpose is to increase energy supplies in the blood to be used as fuel, at the same time it has a direct lowering effect on the immune system. Prolonged aerobic-type exercise or distance running tends to have a greater effect on immunity than short, intense or anaerobic-type exercise probably due to the increased duration of immunosuppression associated with increased cortisol levels. Intense exercise may actually cause a greater release of cortisol due to the increased stress, however the duration of these elevated levels is significantly shorter. This may explain why runners and people that participate in extended aerobic exercise often suffer from upper respiratory tract infections or URTIs.

What can I do to minimize immunosuppression?

Dr Paula Robson of Immunosport at the Sports Science Institute of South Africa suggests the following supplements may help minimize the immune suppression associated with prolonged exercise:

1. Take a multivitamin daily. A supplement that supplies 100% of the RDA has been demonstrated to increase neutrophil function. Neutrophils are a form of lymphocytes white blood cells that make up the immune system.

2. Increase your amount intake of antioxidants. Supplementing the diet with beta-carotene, vitamin C, E and selenium help to neutralize free radicals generated with strenuous exercise. Free radicals tax the immune system and cause oxidative damage in the body including premature aging, arteriosclerosis/hardening of the arteries and cancer.

3. Ingest carbohydrate during exercise. Carbohydrates will help decrease the amount of cortisol released and prevent an excessive drop in blood glutamine levels during exercise. Glutamine is an amino acid that serves as a primary energy source for lymphocytes, which as mentioned, control immunity levels in the body. Also, consuming carbohydrate during exercise stimulates saliva flow, further reducing the likelihood of an URTI from inhaled viruses. As a bonus, carbohydrate intake during exercise will spare protein (muscle) breakdown and minimize hypoglycemic induced fatigue by maintaining blood sugar levels.

4. Supplement with glutamine immediately after endurance exercise - this will help raise blood glutamine levels and indirectly boost immune function. Glutamine levels often fall during recovery from intense exercise, so supplementation with glutamine will also help aid recovery by assisting with regeneration of energy stores and muscle damage repair.

This article has highlighted that simple steps can be taken to minimize the immunosupression associated with prolonged exercise. Assimilating this advice into your training program will help you to be able to stay healthy and train longer and harder this winter.