 
Smokers
could benefit from even a modest addition of vitamin C to their
diet, according to study by UC Berkeley and USDA
03
Feb 2000
By
Robert Sanders Public Affairs
BERKELEY--
A study published this week in the American Journal of Clinical
Nutrition shows clearly that smoking depletes the body of vitamin
C, a powerful antioxidant that protects the body from disease.
However, the study suggests that moderate supplementation can
help smokers boost their vitamin C levels significantly.
Antioxidants
such as vitamin C, vitamin E and carotenoids are thought to
help the body fight off diseases ranging from cancer to heart
disease, and help stave off the degenerative effects of aging.
The
study indicates, too, that previous research that found depleted
vitamin E and carotenoids in smokers may have been measuring
the effect of poor diet, not smoking.
The
study, conducted by scientists at the University of California,
Berkeley, and the U.S. Department of Agriculture's Western Human
Nutrition Research Center (WHNRC) in Davis, was designed specifically
to separate the effects of diet and smoking on antioxidant levels
in the body.
"The
first piece of advice for smokers is, of course, stop smoking,"
said study leader Lynn M. Wallock, PhD, a scientist at UC Berkeley
and the WHNRC. "Barring that, smokers can benefit by improving
their diet to include more fruits and vegetables, which contain
a balance of antioxidants and other nutritional benefits, like
fiber and carotenoids.
"Or,
they can take vitamin C supplements. Even with modest vitamin
C supplementation, smokers can improve their plasma vitamin
C levels substantially. However, no regimen of diet or supplementation
can make up for the adverse consequences of smoking."
The
study was conducted by Wallock, Bruce N. Ames, professor of
molecular and cell biology at UC Berkeley; Jens Lykkesfeldt,
Stephan Christen and Harry H. Chang of UC Berkeley; and Robert
A. Jacob of the Western Human Nutrition Research Center, which
is located at UC Davis but operated by the USDA.
Because
nonsmokers with a poor diet showed increased levels of antioxidants
in their blood after taking vitamin C and E supplements in the
study, the results hint also that supplements can improve the
health of those with poor diets. Supplements, however, cannot
provide all of the health benefits of fruits and vegetables,
Wallock cautions.
The
researchers screened hundreds of male volunteers to find smokers
and nonsmokers with poor diets, looking specifically for low
intake of fruits and vegetables. Anyone taking vitamin supplements
was screened out.
The
reason, Wallock said, is that many previous studies of smokers
have not distinguished the effects of smoking from the effects
of a poor diet, which is common among smokers.
"Smokers
tend to have poor diets, so some effects that have been found
may not be the result of smoking, but the result of not eating
well," she said.
The
volunteers selected for the study averaged 2.7 servings of fruits
and vegetables per day, as compared to the 5-9 servings recommended
by the National Research Council and a minimum of two servings
of fruit and three of vegetables per day.
In
baseline comparisons between the smokers and nonsmokers, smokers
were found to have significantly lower vitamin C levels in blood
plasma than did nonsmokers. However, vitamin E, beta-carotene
and lycopene levels were not significantly different between
smokers and nonsmokers with a poor diet. Lycopene is the major
carotenoid found in tomato products, while beta-carotene is
found in carrots and other orange or red fruits and vegetables.
Wallock
and her team divided the 37 smokers and 38 nonsmokers into two
groups. One received a combined supplement containing vitamins
C and E and folate (272 mg vitamin C, 31 mg alpha-tocopherol,
400 micrograms of folic acid). The other group received placebos.
After
three months, the smokers who took supplements had tripled their
blood levels of vitamin C to bring them up to normal levels.
Nonsmokers taking supplements benefited slightly, too.
Plasma
levels of vitamin E rose in both smokers and nonsmokers, but
the supplement which contained a form of vitamin E called
alpha-tocopherol - actually decreased levels of another form
called gamma-tocopherol. Though Wallock said the health effects
of this are uncertain, at least one study by Ames and Christen
several years ago showed that gamma-tocopherol is nearly as
potent an antioxidant as alpha-tocopherol.
Wallock
continues to analyze results of the study, including the effects
of supplementation on antioxidant levels in sperm.
The
study was supported by the Tobacco Related Diseases Research
Program, the National Institute of Environmental Health Sciences
of the National Institutes of Health and the USDA Agricultural
Research Service.
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