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vitamins, minerals, and colds

A cold is a viral infection that affects the upper airway including the nose, pharynx, throat, and lung airways.

What is the information for this topic? 
Cold viruses are passed easily from one person to another. The best way for a person to avoid picking up cold germs is to wash his or her hands often and to keep hands away from the nose, eyes, and mouth. There is some evidence that both vitamin C and zinc can be effective for preventing or treating colds.

To stay healthy, the body needs vitamin C. Since this vitamin is water soluble, meaning it is not stored in the body, a person needs to eat foods rich in vitamin C daily or take a daily supplement. Research on the effectiveness of large doses of vitamin C for the treatment of the common cold has produced conflicting results. Most findings show that vitamin C has only a small effect on preventing a cold. But they do suggest that vitamin C given at the onset of a cold can reduce how long it lasts.

The best sources of vitamin C are
  • citrus fruits
  • strawberries
  • green and red capsicum
  • tomatoes
  • potatoes
  • leafy greens
  • broccoli
  • spinach
  • tropical fruits - pawpaw, guava, kiwifruit
The recommended daily intake, or RDI, for vitamin C is:
  • 40 mg per day for men
  • 35-40 mg per day for women
  • 30-40 mg per day for children
Smokers are advised to take an extra 35 mg daily. This is because smoking depletes the body of some vitamin C. Pregnant women and women who are breast-feeding need slightly more, too.

Large doses of vitamin C can cause stomach upset, diarrhoea, or kidney stones. The upper level for vitamin C is 2,000 mg per day for adults. People should not routinely go above the set upper levels for vitamins and minerals. An upper level is not the recommended amount to take. It is the maximum amount of a vitamin or mineral that is likely to cause no health risks.

The body needs zinc for more than 200 enzyme activities. There are 2 possible ways this mineral helps prevent and treat the common cold:
  • It stops the growth of the cold virus. Certain viruses do not survive in a zinc-rich environment. This is the rationale behind zinc lozenges.
  • It simulates the immune system. People whose diets lack zinc and people with low blood levels of zinc are more likely to catch a cold or another type of infection.
Best sources of zinc are
  • meat
  • mushrooms
  • oysters
  • eggs
  • brewer's yeast
  • dairy products - milk, yoghurt, cheese
  • legumes - baked beans, kidney beans and soy beans
The recommended daily intake, or RDI, for zinc is 12mg per day for men and women. An extra 4-6 mg per day is needed during pregnancy and breast feeding.

Too much zinc might be as counterproductive to health as too little zinc. Doses of zinc above 100 mg may depress immunity. Zinc in excess of 150mg to 200 mg a day might interfere with copper absorption and could result in a secondary deficiency of this trace mineral. Zinc may also cause stomach upset, nausea and headache.

Author: Dr. Karen Wolfe, MBBS, MA
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 19/06/2005
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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