Study Finds Peril in Taking High Vitamin C Supplement
mistake of confusing a single part of a vitamin for the whole complex]
The New York Times By
Jane E. Brody, April 9,1998
who think that if a little vitamin C is good, more must be better should think again,
team of British researchers, who found that a supplement of 500 milligrams a day
damage people's genes. Many
Americans take that much, or more, in hopes of preventing
colds and reaping the
celebrated antioxidant benefits of vitamin C. Antioxidants, which
molecular damage caused by the highly reactive molecules called free radicals,
believed to protect against heart disease, cancer, eye disorders like cataracts and
degeneration, and other chronic health problems. But
the British researchers, chemical
pathologists at the University of Leicester, found
six-week study of 30 healthy men and
women that a daily 500 milligram supplement
vitamin C had pro-antioxident as well as
antioxidant effects on the genetic material
The researchers found that at the
500-milligram level, vitamin C promoted
damage by free radicals to a part of the DNA,
the adenine bases, that had not
been measured in studies of the vitamin's oxidative
finding, published in the current issue of the British journal Nature,
that have been issued for decades by an American physician, Dr. Victor
professor of medicine at the Mount Sinai School of Medicine in New York.
Herbert has shown, primarily through laboratory studies, that vitamin C
promote the generation of free radicals from iron in the body.
vitamin C in supplements mobilizes harmless ferric iron stored in the body
converts it to harmful ferrous iron, which induces damage to the heart and other
Dr. Herbert said in an interview. "Unlike
the vitamin C naturally present in foods like
orange juice, vitamin C as a
is not an antioxidant," Dr. Herbert said. "It's a redox
agent -- an antioxidant
some circumstances and a pro-oxident in others."
contrast, vitamin C naturally present in food, he said, has no oxidizing effects.
C supplements [ascorbic acid] in large doses have been linked to genetic damage
back as the mid-1970's. In a study then, Canadian researchers found that use of the
in doses larger than in the British study, but not much larger than the amounts
people take to ward off colds and the flu, damaged genetic material in three
bacterial cells, human cells grown in test tubes, and live mice. The
lead author of the
new study. Dr. Ian
Podmore, said that at 500 milligrams, vitamin C did
act as an antioxidant
on one part of the DNA, the guanine bases.
of guanine to oxoguanine is what is
usually measured to determine the degree
damage through oxidation.
expected, when the volunteers took a daily 500-milligram dose of vitamin C for six
oxoguanine levels indeed declined, "which is why vitamin C is generally thought
an antioxidant." Dr. Podmore said. But
when they measured a second indicator of
oxoadenine, the researchers found
that it had risen rather than declined,
"indicating genetic damage to this DNA
Dr. Podmore said. A colleague, Dr. Joseph
Lunec, said that at the 500-milligram
vitamin C's ''protective effect dominated, but
there was also a damaging effect."
should be caution about taking too much vitamin C,"
Dr. Lunec said. The normal
individual would not need to take supplements of vitamin C.
United States and Britain alike, the recommended daily intake of vitamin C for
adults is 60 milligrams, which can be easily obtained from foods by drinking about
ounces of orange juice, for example. Larger amounts are recommended for smokers
for pregnant and lactating women, but even these amounts can be readily obtained
Lunec took issue with the late Dr. Linus C. Pauling, the Nobel laureate chemist who
12,000 milligrams of vitamin C daily and suggested that people could take as much
as they wanted with no ill effect. "We
think that's not the case, to say the least," Dr. Lunec said.
"You can have too
much of a
good thing." The research team is now studying the effects of lower
doses of vitamin
"to see if we can maximize the protective effect and minimize the damage,"
Lunec said. "Given the new finding," he said, "it would be unethical to
test higher levels."