Case for Real Food

Is there more to a carrot than beta carotene? Is lycopene the best we get
from tomatoes? And when we heap our plates with salmon, are we serving up
something other than omega-3s?
For years the scientific community has viewed individual vitamins and
nutrients as the best that food has to offer. Nutrition studies have
isolated beta carotene, calcium, vitamin E and lycopene, among other
nutrients, in order to study their health benefits in the body.
But now, after several vitamin studies have produced disappointing results,
there's a growing belief that food is more than just a sum of its nutrient
parts. In a commentary for the journal Nutrition Reviews, professor of
epidemiology David R. Jacobs argues that nutrition researchers should focus
on whole foods rather than only on single nutrients. "We argue for a need to
return to food as the source of nutrition knowledge,'' writes Dr. Jacobs
with co-author Linda C. Tapsell, a nutrition researcher.
Dr. Jacobs believes that nutrition science needs to consider the effects of
"food synergy,'' the notion that the health benefits of certain foods aren't
likely to come from a single nutrient but rather combinations of compounds
that work better together than apart. "Every food is much more complicated
than any drug,'' said Dr. Jacobs. "It makes sense to want to break it down.
But you get a lot of people talking in the popular press about carbohydrates
and fats in particular as if they were unified entities. They're not. They'
re extremely complicated.''
The narrow focus on the health effects of single nutrients stems from the
earliest days of nutrition research. In 1937, two scientists won a Nobel
Prize for identifying vitamin C as the essential component in citrus fruit
that prevents scurvy. The finding spurred interest by the scientific
community to study other biologically active nutrients in foods.
For as long as observational studies have shown that diets rich in fruits
and vegetables, unsaturated fat and fish, among other things, are associated
with better health, nutrition researchers have been busily deconstructing
these foods to identify the most potent nutrients. For example, vitamin E
has been widely studied as a heart protector.
But attributing the broad health benefits of a diet to a single compound has
proven to be misguided. Several studies have suggested an association
between diets rich in beta carotene and vitamin A, for instance, and lower
risk for many types of cancer. But in a well-known 1994 Finnish study,
smokers who took beta carotene were found to have an 18 percent higher
incidence of lung cancer. In 1996, researchers gave beta carotene and
vitamin A to smokers and workers exposed to asbestos. But the trial had to
be stopped because the people taking the combined therapy showed markedly
higher risks for lung cancer and heart attacks.
Since then, studies of other vitamins, notably vitamins E and B, have also
failed to show a benefit. Manufacturers say the problem is that vitamins are
too often examined in sick people while the real benefit may be in
preventing disease. But Dr. Jacobs notes that the better explanation may
simply be that food synergy, rather than the biological activity of a few
key nutrients, is the real reason that certain diets, like those consumed in
the parts of the Mediterranean and Japan, appear to lower the risks of heart
disease and other health problems.
"People ask me what vitamins they should take,'' said Dr. Jacobs. "I say
'Don't take any. Just make sure you have a nutrient-rich diet.' '' [NYT]