With recent studies suggesting that women who take
multivitamins face increased breast cancer risks, the debate over
whether vitamin supplements are good for us has gained new fuel. Do they
work? Can they harm? Everyone seems to have an opinion.
The Susan Samueli Center for Integrative Medicine asked Frances Jurnak, a UC Irvine physiology & biophysics professor with a personal and professional interest in the health benefits of vitamin use, to address the issue.
Q:
There is a lot of debate over the efficacy of vitamins. How are
multivitamin supplements beneficial?
A: According to Bruce Ames, a famous UC Berkeley researcher in DNA
repair, cancer and aging, a multivitamin supplement is a relatively
inexpensive form of medical insurance. He bases his statements on
laboratory experiments, a review of the medical literature of known
disorders caused by poor vitamin interactions with proteins, as well as
on his biochemical knowledge of how vitamins can be disrupted by genetic
mutations.
Q: What are the differences between taking a multivitamin and
individual vitamin and mineral supplements, like vitamin C or iron?
A:
Unless you need a specific nutrient for medical reasons or are very
knowledgeable about vitamins, you should always take a
multivitamin-mineral supplement. Taking just one type of vitamin can
induce deficiencies of another vitamin. For example, too much vitamin C
can cause a deficiency in vitamin B12. The vitamin companies are aware
of the correct ratios of vitamins and minerals to avoid induced
deficiencies and use the correct ratios in their supplements.
Supplements should contain a mix of both vitamins and minerals, because
the minerals are necessary to activate the vitamins.
Q: Should women be concerned about recent research suggesting that
multivitamin use can increase breast cancer risks? If so, what are the
alternatives?
A: Young women should probably not be concerned
with the recent study on Swedish women. First, there are several
comprehensive American studies indicating that there is no link between
multivitamin supplements and an increased risk for breast cancer in
American women.
As discussed in the recent publication on Swedish women, the most likely factor accounting for the increased risk is folate, which is not added to foods in Sweden, but is added to prepared foods in the U.S. Folate is known to prevent cancer, but if cancer cells are already present, folate may contribute to speeding up the growth of cancerous cells.
Unless young women have a genetic predisposition to cancer, they should not be concerned with taking the daily minimum requirement of folate. As people age and their DNA undergoes mutational changes, they become more at risk for developing cancer. People over the age of 50 might be more concerned about taking extra folate found in most multivitamin supplements.
Q: What other health concerns are associated with multivitamin
use?
A: First, if proper vitamin ratios are not observed, then
vitamins can induce nutrient deficiencies. Second, if megadoses of
vitamins are taken for prolonged periods, like two weeks or more, then
the natural vitamin transporters are diminished in the body. In cases of
megadose-vitamin supplementation, a person needs to be weaned slowly
from vitamins to allow for the vitamin transporters to reappear.
Q: Any other advice?
A: I recommend that all individuals
take a generic multivitamin-mineral supplement, as well as extra vitamin
C (Ester C); an
antioxidant, such as reduced glutathione; and L-carnitine. If a person
has known risk factors for cancer, he or she might want to exclude extra
folate supplementation.
- Tom Vasich, University Communications
