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Lori Shanks
A daily supplementation combination that included folic acid and
vitamin B6 and B12 had no significant effect on the overall risk of
cancer, including breast cancer, among women at high risk of
cardiovascular disease, according to a study in the November 5 issue of
JAMA. Folate, vitamin B6, and vitamin B12 (water-soluble,
essential B vitamins) are thought to play an important role in cancer
prevention. "Background fortification of the food supply with folic
acid (a synthetic form of folate), a policy that began in the United
States in 1998 to reduce risk of neural tube defects, has improved
folate status in the general population. Approximately one-third of
U.S. adults currently take multivitamin supplements containing folic
acid, vitamin B6, and vitamin B12," the authors write. Data from
randomized trials of folic acid alone or in combination with B vitamins
and cancer risk are limited, not entirely consistent, and one trial has
even raised concerns about harmful effects.
Shumin M. Zhang, M.D., Sc.D., of Brigham and Women's Hospital and
Harvard Medical School, Boston, and colleagues conducted a trial to
evaluate the effect of combined folic acid, vitamin B6, and vitamin B12
treatment on cancer risk in women at high risk for cardiovascular
disease. The Women's Antioxidant and Folic Acid Cardiovascular Study
included 5,442 U.S. female health professionals age 42 years or older,
with pre-existing cardiovascular disease or three or more coronary risk
factors, who were randomly assigned to receive either a daily
combination (n = 2,721) of folic acid (2.5 mg.), vitamin B6 (50 mg.),
and vitamin B12 (1 mg.) or a matching placebo (n = 2,721). They were
treated for 7.3 years, from April 1998 through July 2005.
"A total of 379 women developed invasive cancer (187 in the active
treatment group and 192 in the placebo group)," the authors write.
"Compared with placebo, women receiving the active treatment had
similar risk of developing total invasive cancer, breast cancer, or any
cancer death." There were no differences according to current use of
multivitamin supplements, intakes of total folate, vitamin B6, and
vitamin B12, or history of cancer at baseline. Lack of effect for total
invasive cancer did not vary over time.
Age significantly modified the effect of combined B vitamin
treatment on risk of total invasive cancer and breast cancer. A
significantly reduced risk was observed for total invasive cancer and
breast cancer among women age 65 years or older at study entry, but no
reductions in risk were observed among younger women (40-54 years or
55-64 years).
"If the finding is real and substantiated, the results may have
public health significance because the incidence rates of cancer are
high in elderly persons. The finding is biologically plausible because
elderly individuals have increased requirements for these B vitamins,"
the authors write.
"In conclusion, treatment with combined folic acid, vitamin B6, and
vitamin B12 provided neither beneficial nor harmful effects on overall
risk of total cancer, breast cancer, or deaths from cancer among women
at high risk for CVD."
Source: JAMA and Archives Journals
Original Article: Shumin M. Zhang, Nancy R. Cook, Christine M. Albert, J. Michael Gaziano, Julie E. Buring, JoAnn E. Manson. Effect of Combined Folic Acid, Vitamin B6, and Vitamin B12 on Cancer Risk in Women. JAMA. 2008;300(17):2012-2021.
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