| By Katherine Tallmadge
Wednesday, August 25,
2004; Page F01
Many of us want to include nutrients,
the right vitamins and minerals in our diet. But
we often don't want to eat all the foods and calories
required to get this balance. What we're looking
for is a magic supplement that will give us more
energy, improve the quality and length of life and
prevent the chronic diseases of today such as heart
disease, cancer and diabetes.
While we know that certain foods have
been shown to provide these benefits, can the right
supplement do the same?Leading researchers are increasingly
convinced that while supplements can serve many
positive purposes, they cannot take the place of
a well-balanced diet.
"The thousands of vitamins, minerals
and phytochemicals [beneficial plant compounds]
in whole foods act synergistically together to create
a more powerful effect than the sum of their parts,
producing a result which cannot be recreated by
supplements," says Jeff Prince, vice president
for education at the American Institute for Cancer
Research.
Over the past century, nutrition experts
gained a fuller appreciation of the need for a plant-based
diet. Research began to show in the 1970s that certain
patterns of eating, beyond vitamin and mineral intake,
were influencing illnesses. By the 1980s, they found
that populations that ate more fruits, vegetables
and high-fiber foods experienced lower rates of
cancer, heart disease and diabetes. Also, by that
time, discoveries had been made that newly discovered
phytochemicals and certain vitamins and minerals
acted as antioxidants and might prevent chronic
diseases such as cancer and heart disease. After
all, it had been found that people with high blood
levels of two antioxidant vitamins (a form of vitamin
A
called beta carotene and vitamin E) had reduced
lung cancer rates. It had also been observed that
people who ate more dark-green leafy vegetables
(high in beta carotene) experienced less lung cancer,
even if they smoked.
Sensing a major breakthrough, the
National Institutes of Health funded one of the
biggest studies ever conducted. Known as the ATBC
(Alpha-Tocopherol, Beta Carotene) Cancer Prevention
Study, published in the New England Journal of Medicine
in 1994, it tested the theory that the antioxidant
vitamins beta carotene and alpha-tocopherol (vitamin
E) would prevent lung cancer in smokers, the highest-risk
population. After following 29,000 male smokers
for six years, the stunned researchers found "a
higher incidence of lung cancer among the men who
received beta carotene supplements than among those
who did not. In fact, this trial raises the possibility
that these supplements may actually have harmful
as well as beneficial effects."
Needless to say, these revelations
sent shock waves through the scientific community.
"This study was a turning point in the nutrition
field, especially when multiple studies kept confirming
that supplements didn't work at preventing cancers
and heart disease," says David Klurfeld, national
program leader for human nutrition at the USDA's
Agricultural Research Service. "People think
that we can pull out the fiber, pull out the antioxidants.
But research does not back that up. Study after
study says you gain the most benefit from whole
foods."
That is not to say that supplements
are of no use. They can be of great benefit, when
taken based on individualized needs. Most nutrition
experts recommend a daily multivitamin and mineral
tablet for everyone. But supplements simply can't
compete with better food choices. Consider recent
findings:
* When the ATBC Cancer Prevention
study data was re-analyzed years later for consumption
of fruits and vegetables, researchers found that
while supplements did not prevent lung cancer, eating
fruits and vegetables high in beta carotene (e.g.,
carrots, sweet potatoes), lycopene (e.g.,tomatoes)
and lutein/zeaxanthin (deep-green leafy vegetables
such as spinach and kale) reduced lung cancer risk.
* A diet high in cereal and vegetable
fiber (35 grams versus 15 grams) reduces the risk
of colon cancer by 40 percent, according to recent
findings in the EPIC (European Prospective Investigation
into Cancer and Nutrition) study. But studies of
fiber supplements have failed to find any benefits
and some have found an adverse effect.
* A diet high in fruit reduces lung
cancer risk by 40 percent, also according to new
EPIC study findings. Another study found subjects
with a high fruit intake had a 44 percent lower
risk of lung cancer compared with subjects eating
the least amount of fruit. But when subjects added
beta-carotene supplements, there was no benefit
from the fruit.
* Men who ate 10 servings of tomato
products weekly reduced their risk of prostate cancer
by 35 percent compared with men who ate fewer than
1.5 servings, according to a Harvard Health Professional
study. While the benefit is largely attributed to
the phytochemical lycopene, trials of lycopene so
far have found it is less potent than the tomato.
* A diet high in fruits and vegetables
reduced stroke risk by 28 percent, and fruit alone
reduced the risk by 40 percent, according to a study
published in the American Journal of Clinical Nutrition
in 2003. No dietary supplements have been found
that significantly reduce stroke risk.
* People who ate collard greens or
spinach two to four times per week had a 46 percent
decrease in risk for age-related macular degeneration
(the leading cause of blindness) compared with those
who ate these vegetables less than once per month,
according to a study published in the Journal of
the American Medical Association this year. No studies
have found supplements prevent or improve macular
degeneration.
* People who eat more soy have a decreased
risk for coronary heart disease, breast cancer and
prostate cancer. But when various components of
soy foods have been isolated and studied, these
finding have not been replicated, and some have
found adverse effects.
* A diet high in antioxidant-rich
foods helps prevent cardiovascular disease, but
the studies of individual antioxidant supplements
have been so inconclusive that the American Heart
Association recently issued an advisory against
taking them to reduce cardiovascular disease "Researchers
are working as fast as we can to find the most effective
components in foods," says Janet Novotny, research
physiologist at USDA's Human Nutrition Research
Center in Beltsville. "But so far, studies
have shown that while fruits and vegetables are
associated with decreased risk of chronic disease,
studies of the isolated compounds in fruits and
vegetables haven't shown an effect."
Food and dietary patterns are
complicated and expensive to study, and can defy
the brightest minds and best intentions. In the
meantime, the best advice is to eat a plant-based
diet with at least five to nine servings of fruits
and vegetables (you'll get the most benefit with
the higher amount), at least three to four servings
of whole grains and regularly eat legumes as a side
dish or occasionally as your protein source.
© 2004 The Washington
Post Company
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