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Original Contribution
November 5, 2008

Effect of Combined Folic Acid, Vitamin B6, and Vitamin B12 on Cancer Risk in Women: A Randomized Trial

Author Affiliations

Author Affiliations: Divisions of Preventive Medicine (Drs Zhang, Cook, Albert, Gaziano, Buring, and Manson) and Aging (Drs Gaziano and Buring), Department of Medicine, Brigham and Women's Hospital and Harvard Medical School; Department of Epidemiology, Harvard School of Public Health (Drs Cook, Buring, and Manson); Veterans Affairs Boston Healthcare System (Dr Gaziano); and Department of Ambulatory Care and Prevention, Harvard Medical School (Dr Buring), Boston, Massachusetts.

JAMA. 2008;300(17):2012-2021. doi:10.1001/jama.2008.555

Context Folate, vitamin B6, and vitamin B12 are thought to play an important role in cancer prevention.

Objective 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.

Design, Setting, and Participants In the Women's Antioxidant and Folic Acid Cardiovascular Study, 5442 US female health professionals aged 42 years or older, with preexisting cardiovascular disease or 3 or more coronary risk factors, were randomly assigned to receive either a daily combination of folic acid, vitamin B6, and vitamin B12 or a matching placebo. They were treated for 7.3 years from April 1998 through July 31, 2005.

Intervention Daily supplementation of a combination of 2.5 mg of folic acid, 50 mg of vitamin B6, and 1 mg of vitamin B12 (n = 2721) or placebo (n = 2721).

Main Outcome Measures Confirmed newly diagnosed total invasive cancer or breast cancer.

Results A total of 379 women developed invasive cancer (187 in the active treatment group and 192 in the placebo group). Compared with placebo, women receiving the active treatment had similar risk of developing total invasive cancer (101.1/10 000 person-years for the active treatment group vs 104.3/10 000 person-years for placebo group; hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.79-1.18; P = .75), breast cancer (37.8/10 000 person-years vs 45.6/10 000 person-years, respectively; HR, 0.83; 95% CI, 0.60-1.14; P = .24), or any cancer death (24.6/10 000 person-years vs 30.1/10 000 person-years, respectively; HR, 0.82; 95% CI, 0.56-1.21; P = .32).

Conclusion Combined folic acid, vitamin B6, and vitamin B12 treatment had no significant effect on overall risk of total invasive cancer or breast cancer among women during the folic acid fortification era.

Trial Registration clinicaltrials.gov Identifier: NCT00000541