Nutrition for winter – zinc.

Do you need more zinc in winter to fight colds?  The manufacturers of zinc-containing lozenges and supplements would like you to believe that.  They took a nutritional fact – zinc is important for immune function – and leapt to the conclusion that more zinc would therefore mean even better immune function, and head colds would magically fade away.  You know, like saying if your car needs 4 quarts of oil, it will run even better if you dump 100 more quarts over the engine.

Too much of a good thing isn’t necessarily good.  The marketing ploy for zinc nasal sprays was based on the same simplistic conclusions, until some of the products were found to cause anosmia, or loss of smell, due to the zinc.  The products were withdrawn from the market, and lawyers hunted for victims to join lawsuits against the manufacturers.  Zinc-containing denture adhesives recently made news, when some users developed zinc toxicity, leading to anemia, neuropathy and copper-deficiency symptoms.  Zinc is a key nutrient, but too much is a bad thing.

Some zinc facts:

  • Oysters have the highest zinc content: almost 77 mg in just 6 medium oysters, compared to about 9 mg in 3 oz of steak.
  • The recommended daily intake for adult men is 11 mg/day; 8 mg/day for adult women.
  • Zinc intake may decrease as people age.  Why?  Perhaps people eat fewer high zinc foods like red meats, dairy, shell fish, nuts and beans.  Perhaps absorption changes.  Alcohol and certain fibers interfere with absorption.
  • Over 100 enzymes in the human body include zinc.  It’s important for protein structures, cell membranes, immunity, reproduction and gene expression.

But does it cure colds?  There isn’t much hard evidence.  Some studies suggested that zinc lozenges may shorten the length of a cold, if taken every few hours for up to 5 days.  Long term use of lozenges is not recommended, and will not prevent colds.   Children and pregnant women also should be cautious, since zinc toxicity is a risk.  Your best plan is to get enough zinc from diet.  Most multiple vitamin/mineral supplements have zinc up to the recommended daily intake level, and some cereals are fortified with it.  If you take a multiple and are a frequent meat-eater, you might already be consuming plenty of zinc.  If you don’t take supplements, and are vegetarian or vegan, you could have a marginal intake.  Some experts believe low-level zinc insufficiency is wide spread, but there isn’t a reliable standardized test to confirm deficiency.  In addition to vegetarian/vegans, the people most at risk of deficiency are: the elderly, anyone with gastro-intestinal diseases that causes malabsorption, anorexics, alcoholics, infants and children, pregnant women.

The Big Picture message: short-term use of zinc lozenges may or may not shorten your cold.  Zinc won’t prevent colds, and long term use of high dose zinc supplements could cause problems.

For more detailed information on zinc:

Linus Pauling Institute

NIH Office of Dietary Supplements

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