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Maintaining Good Immune Function


January 16, 2012 by peakcentre

By Ed McNeely

The arrival of fall ushers in the end of the summer sport season and the beginning of cold and flu season. Endurance athletes area at greater risk of developing upper respiratory tract infections than non athletes, particularly during periods of heavy training and stress. Getting sick or injured can be one of the biggest impediments to a good winter of training. If you have an illness that drags on it may cause your training volume and quality to drop enough that your spring racing may be affected.

Besides avoiding all human contact, which is impractical and frequent hand washing, which we should all be doing there are a few training and nutritional practices that can help you maintain good immune function this winter.

 Gradual Volume Increases

Sudden increases in volume, the number of hours per week that you are training, seem to trigger greater immune suppression and increase the likely hood of injury. Most people will take a month or more off after their final race. Plan your transition period and the date when you start back into training early enough in the year that you can work back into training gradually. Start with about 60% of the peak training volume you used the previous season and build your volume each week. Maximum increase in training volume from week to week should not be more than 10% of the previous week’s volume.

 Plan for External Stress

External stressors are a part of life and can combine with training stress to decrease immune function. Many of them are unexpected but there are those that can be predicted and built into the training plan. Exam periods for student athletes are set far enough in advance that they can be built into the training plan. Busy periods at work often can be predicted and planned. Holidays occur at the same time every year. Recovery weeks and decreased periods of training volume should be planned to coincide with these external stressors.

 Vitamins and Minerals

One of the keys to maintaining a healthy immune system is to avoid deficiencies of the nutrients that play a key role in immune function. Deficiencies of vitamins A, E, C, B6, B12 and folic acid decrease resistance to infection, as can deficiencies in zinc, iron, magnesium, and selenium. Correcting deficiencies can restore normal immune function. Does this mean that you should be taking mega doses of vitamins and minerals? Definitely not. Magnesium and selenium deficiencies are rare. While zinc and iron deficiencies are common in athletes you need to be careful when supplementing these minerals, excessive zinc and iron can also have a negative impact on immune function. You can monitor your need for iron and zinc with simple blood tests, serum ferritin and hemoglobin for iron and erythrocyte zinc for zinc status.

If you are eating a well balanced diet with lots of fruits and vegetables you probably do not need a vitamin supplement; if you don’t eat a lot of fruits and vegetables a daily multi vitamin/mineral supplement will probably be beneficial. Excessive intakes of Vitamins A and E can lead to immune system suppression and other toxic effects. Vitamin C supplementation of up to 800mg per day does seem to have a beneficial effect on immune function during hard training or racing.


Getting adequate energy and carbohydrate are the most important factor in maintaining good immune function. When carbohydrate stores become depleted during exercise cortisol levels start to rise. Cortisol is a catabolic hormone in the body that breaks down various substances and tissues for energy. High levels of cortisol suppress immune function, decrease bone density, and break down muscle tissue. Consuming carbohydrates during and immediately post exercise can decrease cortisol levels and help maintain good immune health.  Consume 30-60g of carbohydrate per hour during training in a drink that provides 4-8g of carbs per 100ml.

The addition of protein to your post workout recovery drink will enhance the uptake of the carbohydrate and has been shown to decrease muscle breakdown more effectively than carbohydrate alone. The addition of protein also stimulates the development of new muscle proteins, which are essential for training adaptations to occur. Your post workout recovery drink should have approximately 1g of protein for every 2-3 g of carbohydrate.


It has been well established that an inadequate intake of protein impairs immunity. Many athletes become so focused on carbohydrate intake that they are protein malnourished. Extremely high volumes of training can also lead to protein malnourishment if protein becomes a source of fuel for training sessions. Early morning training, prior to food intake, and multiple higher intensity training sessions in a day are major culprits in the development of protein nutrition problems. Endurance athletes should be consuming 1.2-1.6 g of protein per kilogram of body weight. If you are training more than 15 hours per week your protein need may be even higher and should be determined by nutrition professional.

 Other Nutritional Substances

Other nutrients and nutritional substances have been promoted as having a positive effect on immune function; athletes and non-athletes frequently use Echinacea, glutamine, and oregano oil alike. The research on these substances is mixed; some studies show positive effects on immune function or in the reduction of upper respiratory tract infections while others have shown no effect. This may be due to differences in the quality of the product, dose size and immune status. Consult with your physician or nutrition professional before using these substances.


Nobody likes to get sick. Following some of these suggestions may help you prevent illnesses this winter and still keep your training volume and intensity where it needs to be to perform at your best next spring and summer.

1 comment

  1. Trudy says:

    You make tnhigs so clear. Thanks for taking the time!

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