Multivitamins don’t promote longevity in older women

Older women who take multivitamins and other supplements don’t live longer and may even die at somewhat higher rates than women who don’t use supplements, a new study has found.

Researchers examined data from nearly 38,772 older women, mean age 61.6 years at baseline, who participated in the Iowa Women’s Health Study and filled out questionnaires on supplement use in 1986, 1997, and 2004. The questionnaires asked about multivitamins, vitamins A, C, D, and E, beta carotene, B vitamins, and minerals such as calcium, iron, copper, magnesium, selenium, and zinc. Among the 15,594 women (40.2%) who died between 1986 and 2004, total mortality risk was higher in users than in nonusers of multivitamins (2.4% absolute risk increase), vitamin B6 (4.1%), folic acid (5.9%), iron (3.9%), magnesium (3.6%), zinc (3%), and copper (18%). Forty-one percent of multivitamin users died, compared with 40% of nonusers; the difference widened when health problems such as diabetes, hypertension, and overweight were taken into account.

The study was published in the Archives of Internal Medicine(2011;171[18]:1625-1633).

The association between supplements and higher total mortality risk “is strongest with supplemental iron,” the authors write. “In contrast to the findings of many studies, calcium is associated with decreased risk.” Calcium was the only supplement linked to a reduced risk of death (absolute risk reduction, 3.8%). Thirty-seven percent of calcium users died compared with 43% of nonusers, an association that persisted even after accounting for healthier lifestyles among users.

The findings don’t establish that supplements are harmful, warns lead author Jaakko Mursu, PhD. He prefers the conclusion that they show no evidence of benefit.  

Supplement use increased over the course of the study. Between 1986 and 2004, the proportion of women who said they took one or more supplements rose from 63% to 85%. 

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