A small study of 67 nonsmokers exposed to environmental smoke showed those
who took 500 mg of vitamin C daily had lower levels of a compound linked to the
damage done by tobacco smoke.
The study did not last long enough to tell whether the vitamin takers were
less likely to have cancer or heart disease, but Marion Dietrich of the
University of California, Berkeley, who led the study, found the results
encouraging.
"They show that vitamin C may help protect nonsmokers from the oxidative
damage caused by second-hand tobacco smoke," Dietrich, a nutritional
epidemiologist, said in a statement.
Oxidative damage has been compared to rust damaging metal. It is caused by
charged particles known as free radicals, and can be counteracted by
antioxidants including vitamin C.
But what works in a lab dish does not always hold true in the human body.
Writing in Tuesday's issue of the journal Nutrition and Cancer, Dietrich and
other researchers tested for levels of F2-isoprostanes, which are generated
through a form of oxidative stress called lipid peroxidation.
This can damage the cell membrane and help form plaque that blocks arteries.
The 67 volunteers, all nonsmokers exposed to second-hand smoke, were randomly
assigned to one of three groups.
One group took 500 mg of vitamin C a day, a second group took vitamin C,
vitamin E and the antioxidant alpha-lipoic acid (ALA), and a third group took
daily placebo capsules.
After two months, blood levels of F2-isoprostanes dropped by 11.4 percent for
the vitamin C group compared with those taking the dummy capsule, and 12 percent
for the C plus E plus ALA group.
VITAMIN E ADDED LITTLE BENEFIT
Adding E and ALA did not help much.
"That was a surprise to us," Gladys Block, a professor of nutritional
epidemiology at Berkeley's School of Public Health who worked on the study, said
in a telephone interview.
The volunteers were told not to take any other vitamins for several weeks
before the study started, and people who reported eating plenty of fruits and
vegetables were excluded.
"The evidence is overwhelmingly consistent that people who eat a lot of
fruits and vegetables have a lower risk of cancer," Block said.
Such people may already have so many antioxidants in their system that they
would not benefit from taking vitamins, she said.
Block said the group did a study last year that showed smokers could lower
markers of oxidative damage by taking vitamin C.
But she said she hoped the findings would not lead people to think they can
pop vitamins and escape the consequences of unhealthy habits.
"The message of the study is clearly not that taking vitamin C makes smoking
or exposing others to smoke OK," she said. "But, if you are in a situation where
you cannot escape frequent exposure to second-hand smoke, it may be worthwhile
to take vitamin C supplements as a precautionary measure. And, as always, eat a
diet rich in fruits and vegetables."
SOURCE: Nutrition and Cancer 2003.
