The key to preventing or lessening the severity of cold and flu symptoms is maintaining a healthy, effective immune system.  The best way to ensure this is through proper nutrition from your diet and appropriate supplementation.
Let’s look at a few of the nutrients which help us to stay healthy:
- Vitamin C stimulates the immune system’s ability to produce interferon, a natural virus-killing glycoprotein.
Hundreds of studies reveal that consuming generous amounts of vitamin C can empower the activity of white blood cells by anywhere from 100% to 300%.  Individuals who take 1 to 3 g of vitamin C daily consistently report fewer colds than the ones who do not supplement with this vitamin.
In a study conducted by the Naval Medical Research Institute, vitamin C plasma levels of 28 men on a 68-day submarine patrol were checked frequently.  The ones with the lowest plasma levels of this vitamin came down with twice as many colds as did the sailors with the highest vitamin C plasma levels.
The biochemist G. Ritzel conducted a controlled study with school-aged boys.  Those who began taking 1,000 mg of vitamin C per day reported that their number of colds decreased by 45% and their sick days per cold decreased by 30%.
A recommended dosage of vitamin C for boosting your immunity is 250-500 mg two to three times daily.
- Well-documented for protecting mucous membranes, Vitamin A is another preventer of colds and flus because it boosts the immune system.  Naturally-occurring vitamin A is fat soluble and stored in the liver; it can, therefore, be toxic in large amountsalthough most people must take at least 100,000 IU of active vitamin A daily for a period of months before developing any signs of toxicity.
A recommended immune-boosting dosage is 5,000-10,000 IU of vitamin A per day.
- What is not generally known is that many of the B-complex vitamins are crucial to the immune system’s ability to defend us.  According to Mark Mayell in Off-the-Shelf Natural Health, “Vitamin B6 is the most important of the B vitamins for keeping your immune system working optimally.”
- Zinc supplementation multiplies the number of white blood cells, lymphocytes, and cellular antibodies and revs up their fighting ability.  Zinc deficiency seems to play a role in the development of auto-immune diseases, in which the immune system attacks itself or other body tissue.
- Vitamin E enjoys a growing reputation as an immune stimulant that can boost the body’s ability to resist various diseases.  Studies indicate that taking optimal levels of vitamin E improves antibody response and T-cell activity.  Vitamin E’s effect on the immune system is thought to be partially due to its role as an antioxidant that protects the thymus and lymphatic tissue.
- One of the great American folk remedies is the immune-stimulator echinacea, used for centuries by Native Americans to conquer colds.  Echinacea’s reputation as a substance that activates white blood cells, boosts the immune system, and short-circuits colds and other respiratory infections has made it America’s most popular healing herb.

Reference: Langer, Stephen, M.D., and Scheer, James F.  Solved: The Riddle of Illness, Second Edition.  New Canaan, CT, 1995.