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Sheila's Nutrition Digest Vol 10 - Tips for fighting colds and flu
By:  Sheila Kealey   (2005/11/30)

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Cold and flu season is upon us. While no one likes getting sick, illness can have far reaching effects among athletes if it strikes during an important competition or compromises an extended period of training.

Athletes may be more vulnerable to infection, according to some research. Although in the long term, exercise will strengthen your immune system, intense or prolonged exercise can depress immune function temporarily. After hard training, researchers have observed decreased blood concentration of glutamine, increased cortisol levels, a drop in lymphocyte production, and decreased T-cell activity, changes that indicate an immune system that is more susceptible to infection.

But all sickness isnít inevitable: you can take precautions that will greatly reduce your chances of getting sick. Since Iím writing a nutrition column, Iíll focus on dietary measures, but feel obliged to highlight the following, since their impact on illness is likely much greater than diet:

  • Get a flu shot. Itís the most effective way to prevent the flu.
  • Wash your hands often with plain soap and hot water. Cold and flu viruses are spread by direct contact. Germs can live for hours on phones, keyboards, doorknobs, etc, ready to be picked up by unsuspecting hands. If youíre not near a sink, rubbing your hands together quickly for about a minute can help break up cold germs.
  • Avoid touching your eyes, nose, or mouth since they are the route that most cold and flu viruses enter your body.
  • Limit exposure to infected people.
  • Get enough sleep

DIET HABITS THAT STRENGTHEN THE IMMUNE SYSTEM

A well-balanced diet that is nutrient rich can help boost your immune system. Including the following foods in your daily diet will keep your bodyís defenses primed to fight off incoming viruses.

Fruits and Vegetables

Fruits and vegetables contain natural compounds like phytochemicals, antioxidants, and vitamins, which enhance your immune system. Here are some examples:

Brightly colored fruits and vegetables are especially good sources of protective substances. For example, foods like carrots, sweet potatoes, spinach and other dark greens contain beta-carotene, which can increase the number of infection-fighting cells, white blood cells (sometimes called ďnatural killer cellsĒ), and helper T-cells. Your body converts beta-carotene to vitamin A, which also helps your immune system by enhancing white blood cell function. Tomato products are especially rich in lycopene, a carotenoid that enhances the production of white blood cells to help destroy many types of viruses.

Garlic and onions. Recent research adds credibility to the folklore claiming that onion juice or garlic cloves ward off colds and flu. The sulfur-containing substances in these flavorful foods play an important role in stimulating the immune system by boosting the killing ability of natural killer cells.

 

Carbohydrates

Athletes who donít consume sufficient carbohydrates may decrease their ability to fight off infections following intense or prolonged exercise. According to some studies, ingesting carbohydrates during and immediately after exercise can help prevent sickness by reducing cortisol levels and maintaining lymphocyte production. This is another good reason to consume an energy drink or other carbs during your workout, and pay attention to post-workout nutrition (see Vol. 1 - Refueling for Recovery).

Protein

Your immune system produces antibodies when viruses invade the body. Antibodies, which are proteins made up of certain amino acids, bind to the invading substances to try to destroy them. A healthy diet should contain high quality protein (that contains the 8 essential amino acids).

Healthy Fats

The omega-3 fats are important for a healthy immune system. Youíll find these fats mainly in fatty fish like salmon, sardines, trout and herring, and smaller amounts in walnuts, flaxseed, soybeans, wheat germ, canola oil, and green leafy vegetables. One British study showed that omega-3 fats boosted levels of T cells and virus-fighting interferon-gamma cytokines in test subjects.

 

Yogurt

Preliminary research suggests that eating a cup of low-fat yogurt daily can reduce your susceptibility to colds. The beneficial bacteria (called probiotic) in some yogurts is thought to boost the immune system.

 

Zinc

Zinc is a trace mineral that is important for proper immune functioning. Studies have shown that it can help weaken the cold virus and minimize the duration and severity of cold and flu symptoms. Good food sources of zinc include oysters, beef, chicken, turkey, lamb, and crab.

 

What about supplements?

There is no convincing evidence to suggest that supplements boost immunity in healthy individuals, although they may help malnourished or some individuals deficient in critical nutrients (e.g., vitamin C, certain B vitamins, iron, and zinc). Also, itís important to consider research showing that megadoses of certain vitamins can actually suppress the immune system. For example, zinc is important for immune function, but high dose supplements may actually suppress immune response.

The Bottom Line

Your best bet for a strong immune system is to follow the non-dietary tips above, and consume a nutrient-dense diet that is rich in antioxidants, vitamins, and other protective nutrients.

 
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