Multivitamin use not associated with reduced cancer, CVD risk

Little or no effect reported on various risks in postmenopausal women.

Multivitamin use had minimal or no influence on risk for several types of cancer, for CVD or for mortality, results from a study suggested.

The study included 161,808 participants from the Women’s Health Initiative who were enrolled between 1993 and 1998. The researchers created a study cohort of 68,132 participants from the clinical trials of the initiative and 93,676 from an observational study of the initiative. For the combined study cohort, 41.5% of the participants reported using multivitamins. Participants were followed up for a median of 8.0 years in the clinical trials cohort and 7.9 years in the observational study cohort.

After adjusting for multiple variables, the researchers suggested that there was no association of multivitamin use with a 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). Multivitamin use was also not associated with a risk reduction for MI (HR=0.96; 95% CI, 0.89-1.03), stroke (HR=0.99; 95% CI, 0.91-1.07) or venous thromboembolism (HR=1.05; 95% CI, 0.85-1.29). There was also no reported association between multivitamin use and total mortality (HR=1.02; 95% CI, 0.97-1.07).

“Nutritional efforts should remain a principal focus of chronic disease prevention, but without definitive results from a randomized controlled trial, multivitamin supplements will not likely play a major role in such prevention efforts,” the researchers wrote. – by Eric Raible

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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