Multivitamin use not associated with lower risk for CVD, cancer, death in postmenopausal women

Long-term multivitamin use had no effect on the risk for common cancers, cardiovascular disease and overall mortality in postmenopausal women, according to results from the WHI.

The researchers analyzed data from 161,808 participants — 68,132 women from three clinical trials conducted to test hormone therapy, dietary modification and calcium and vitamin D supplements and 93,676 women who were part of an observational study. Women were enrolled in the WHI between 1993 and 1998.

A total of 41.5% of women used multivitamins. Multivitamin users were more likely to be white, live in the Western United States, have a lower BMI, be more physically active, drink more alcohol, eat more fruits and vegetables and have at least a college degree compared with nonusers.

During an average eight years of follow-up, 9,619 cases of breast, colorectal, endometrial, renal, bladder, stomach, lung or ovarian cancer developed, and 8,751 CVD events and 9,865 deaths were reported.

After multivariate adjustment, there was no association between multivitamin use and risk for breast cancer (HR=0.98; 95% CI, 0.91-1.05), colorectal cancer (HR=0.99; 95% CI, 0.88-1.11), endometrial cancer (HR=1.05; 95% CI, 0.90-1.21), lung cancer (HR=1.0; 95% CI, 0.88-1.13) or ovarian cancer (HR=1.07; 95% CI, 0.88-1.29). The researchers reported the same for CVD — MI (HR=0.96; 95% CI, 0.89-1.03), stroke (HR=0.99; 95% CI, 0.91-1.07), venous thromboembolism (HR=1.05; 95% CI, 0.85-1.29) and death (HR=1.02; 95% CI, 0.97-1.07). – by Katie Kalvaitis

Arch Intern Med. 2009;169:294-304.

Prior study using randomized, controlled trial design in people with diabetes and the elderly suggested that multivitamins were modestly helpful for reduction of pneumonia and comorbidity. This observational study design does not mirror these results potentially because of healthy-user bias related to a healthy and younger population such that multivitamins do not make healthy people healthier. In addition, the over-the-counter market is deregulated and multivitamins in the community (as opposed to those in a randomized clinical trial) may include multivitamins that have ingredients that are not effective or frankly harmful, which could zero out a beneficial effect.

– C. Noel Bairey Merz, MD

Director, Preventive and Rehabilitative Cardiac Center
Cedars-Sinai Medical Center, Los Angeles

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