Tables Turn on Building Immunity
Research Finds Proper Diet
Outdoes Taking High Doses
Of Nutritional Supplements
October 19, 2005; Page D7

As cold-and-flu season arrives, so do the pitches for products that
claim to increase the body's natural immunity and ward off infection.
And with alarming reports about avian flu and a threatened global
pandemic, it may be tempting to load up on mega doses of vitamins,
minerals and herbal supplements as an added precaution.

But as scientists delve more deeply into how the immune system works,
they are finding evidence that it is the complex interaction of
nutrients in food that helps the body build its defenses against
disease and infection, in part by controlling some types of
inflammation that can weaken the immune system. Single nutrients and
cocktails of nutrients consumed alone can't provide the same benefit,
they warn, and large does of some supplements such as selenium, zinc,
vitamin A, vitamin B6 and vitamin E may even harm and suppress the
immune response.

The best defense against influenza is getting vaccinated as soon as
possible -- and the most important way to prevent the spread of colds
is frequent hand washing. But experts say that following the most
basic tenets of good nutrition -- consuming a balanced diet rich in
fruits and vegetables and low in saturated fats, and eliminating
highly processed and junk foods -- can actually help ward off illness.

"There is lot people can do with proper nutrition to improve their
chances of warding off the flu or making the disease less pathogenic,"
or harmful, says Simin Nikbin Meydani, director of the nutritional
immunology laboratory at Tufts University's Jean Mayer USDA Human
Nutrition Research Center on Aging.

Exercise and maintaining a normal weight are equally important, Dr.
Meydani adds, because obesity can also impair immune function and make
people more susceptible to many types of infections. Tufts researchers
have shown that moderate caloric restriction in humans appears to be
beneficial for immunity.

In a paper published this year in the Journal of the American Medical
Association, Tufts researchers said there is no consistent or
significant effect of any single vitamin or combination of vitamins on
the incidence of disease, while a growing body of research shows that
a healthy diet can help decrease the risks. (The 2005 U.S. Dietary
Guidelines,
www.health.gov/dietaryguidelines/dga2005/recommendations.htm1, help
consumers find which foods deliver the best balance of nutrients).

In a healthy immune system, studies show, after an injury or cut, the
body's inflammatory response combats the damage. Poor nutrition can
lead to chronic inflammation, thereby weakening the immune system and
making the body vulnerable to an array of illnesses, says Mehmet Oz, a
professor of cardiac surgery at New York's Columbia University, and
co-author of the book, "You: The Owner's Manual."

Dr. Oz says a single multivitamin can be beneficial, such as one that
contains at least 800 micrograms of folate, 400 international units --
or IUs -- of vitamin D, 1,200 milligrams of calcium and 400 milligrams
of magnesium. But he says only a healthy diet can provide the
inflammation-fighting nutrients that may protect against colds and flu
in the short term and potentially fight diseases such as Alzheimer's,
cancer and heart disease over time.

To be sure, researchers say, more study needs to be done on vitamins.
A widely reported study in the New England Journal of Medicine last
spring warned that taking the commonly used dosage of vitamin E -- 400
IUs -- carries risks for cardiac patients. But in a study of 617
nursing-home residents, Tufts researchers found that smaller doses of
vitamin E -- 200 IUs daily, or half the dose of most supplements --
significantly reduced the incidence of common colds.

In its wellness guide for consumers (www.berkelywellness.com2),
experts at the University of California at Berkeley warn to be wary of
any supplement that promises to raise immunity, such as protein
supplements, enzyme supplements and specific vitamins and minerals. It
also warns against products such as nasal pumps containing zinc, which
claim to reduce cold severity and duration but may also cause loss of
smell, and says there is no evidence of effectiveness for tablets that
dissolve in water and contain high doses of vitamins A, C or E,
Chinese herbs, magnesium, selenium and zinc.

The federally funded National Center for Complementary and Alternative
Medicine (nccam.nih.gov3) is paying for studies into a number of
herbal compounds. The New England Journal of Medicine reported in July
that a study funded by the center found that none of three
preparations of the most commonly used herbal preparation, echinacea,
had any effect on whether study volunteers became infected with the
cold virus or on the severity or duration of symptoms among those who
developed colds. However, critics of this study -- mostly herbal
supplement makers -- protested that the doses studied were too low,
and additional studies are under way.
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