udging from the torrent of advice from our friends, relatives,
coworkers and the blogosphere, we are a nation of experts on diet
and nutrition. But when experts disagree, as they often do (even
the  scientists),
who knows what to believe?
In the interest of clarification, the Center for Science in the
Public Interest has published 10 common misconceptions about diet
and health and how they got started. Here are just a few:
It’s OK for older people to
be overweight. The dangers of obesity are well
documented, but a 2007 survey of older people reported that being
merely overweight was not a problem and that overweight people
actually had a lower risk of dying from emphysema, pneumonia,
TB, and Alzheimer’s disease than those of normal weight.
This research was flawed, however, says JoAnn Manson of the Harvard
Medical School. “When people have underlying chronic diseases
that lead to weight loss, they shift into lower-weight categories,
and that makes leaner people look worse off than the overweight.”
She suggested that midlife weight measurements are more reliable.
Butter is better for you than margarine.
Granted, butter may taste better, but it is still high in saturated
fat. And nearly all of the popular margarines have switched from
the damaging trans fats, also known as or “partially hydrogenated
oils,” to a mix of unsaturated oils with smaller amounts
of saturated fats (just be sure to check the label to make sure
there’s no trans fat). If you still prefer butter as a spread,
try the whipped or light varieties with less saturated fat.
You don’t need to worry about
getting enough protein. Because the typical American
diet is so high in protein, people naturally assume they’re
getting enough. But a USDA survey has found that 15 percent of
people in their 60’s and 40 percent of 75-year-olds are
not eating the Recommended Dietary Allowance of protein (46 grams
a day for women, 56 for men).
As people get older, their calorie needs go down and they tend
to eat less, explains Purdue University nutritionist Wayne Campbell.
But our protein needs do not drop as we get older. And eating
too little protein leads to lost muscle and weakness. Another
group at risk for too little protein is dieters of all ages.
Calcium is the only key to strong
bones. The message that calcium builds and maintains
strong bones has been repeated so often, we may assume it’s
all that matters. But healthy bones also need vitamin D, and many
of us are not getting enough. The RDA for vitamin D is 400 IU
a day but 1,000 is recommended for anyone who’s of middle-age
or older. “Almost everyone working in this field agrees
that the vitamin D recommendations are too low,” says Susan
Harris of the Tufts University Human Nutrition Research Center
on Aging. What also helps is daily exercise and a diet rich in
fruits and vegetables.
Echinacea prevents colds. In three major clinical
trials, the herb Echinacea was no better than a placebo at preventing
colds. But in seven of ten studies, participants who took Echinacea
after they got sick had slightly shorter or milder colds. The
same can be said for vitamin C. In 29 studies of more than 11,000
people who took from 200 to 2,000 mg of vitamin C a day, this
did not ward off colds. But those who took about 1,000 mg a day
before and while they were sick were more likely to have shorter,
milder colds. 
—To
see all 10 nutrition myths, visit www.cspinet.org
(Jan.-Feb. 2008 issue).
Nutrition myths and how they grew (click)
Are fish-oil pills the same as eating fish? (click)
Danish study on knee pain and weight loss (click)
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