A report released earlier this week in the Archives of Internal Medicine indicates that older women slightly increase their risk of dying by taking supplements like iron but slightly decrease this risk with calcium supplementation.
If you’re the one in two adults who regularly takes a multivitamin or other supplement, this news may be somewhat confusing. Below we review the study design and research results then provide insight into their findings.
Iowa Women’s Health Study
Data was obtained from participants enrolled in the Iowa Women’s Health Study. This large study was designed to examine associations between dietary and lifestyle factors and the incidence of cancer in postmenopausal women.
The aim of the current study was to examine the association of vitamin and mineral supplementation and mortality in older women.
Almost 39,000 women (average age 62 years) participated in the study when it began in 1986. Study participants were white (99.2%) and postmenopausal (98.6%). About two-thirds of participants were supplement users; the remaining third were non-supplement users.
Food intake was assessed at baseline and in 2004 using a food frequency questionnaire. Self-reported use of fifteen supplements was measured at three intervals: 1986, 1997 and 2004. In 1986, 66% of the women used supplements. By 2004, that proportion had increased to 84%.
At baseline, supplement users were better educated, more likely to use hormone therapy and were healthier (lower incidence of high blood pressure, diabetes, lower BMI, greater physical activity, lower prevalence of smoking) than non-supplement users.
After 19 years of follow-up, 15,594 or 40% of study participants had died.
After adjusting for age and caloric intake, use of the B-complex, vitamin C, vitamin D, vitamin E and calcium had significantly lower risk of mortality compared with non-use. However, use of copper supplements was associated with higher risk of death.
When researchers further controlled for education, place of residence, health-related measures and diet, the use of multivitamins, vitamin B6, folic acid, iron, magnesium, zinc and copper were associated with a slightly increased risk of death in the study population. The use of calcium supplements still reduced the risk of mortality.
Analysis of shorter follow-up intervals at four, six and ten years, showed that the most consistent findings were that mortality risk was positively associated with supplemental iron and inversely related with supplemental calcium.
Miriam Pappo, director of clinical nutrition at Montefiore Medical Center, said the findings likely won’t drive doctors to stop recommending multivitamins to help patients get all the nutrients they need.
“No one disputes that the oral intake of food to get your vitamins and minerals is the way to go,” said Ms. Pappo. However, “in reality, most of us don’t make it up to the nine servings a day of fruits and vegetables.”
Susan Fisher, chairwoman of the University of Rochester School of Medicine and Dentistry’s Department of Community and Preventive Medicine said that factors besides supplement use may have shaped the results. She pointed out, “the use of hormone therapy to treat the symptoms of menopause was nearly twice as common among supplement users as among nonusers. Some forms of hormone therapy have been linked to an increased risk of heart disease and cancer.”
Fisher also noted that the study looks at deaths and not the chronic health conditions that supplements can prevent.
The Bottom Line
Adults who take nutritional supplements are generally healthier than non-supplement users. So, why is it that this study found a small increase in risk of death in older women that took certain supplements?
From a study design standpoint, participants were white, older women, living primarily in a rural area. These findings may not apply to other races, groups, geographical areas or men.
Additionally, the women had to recall their supplement use on three occasions over a 19 year period. Think about the difficulty in having to recall your supplement use over the past 7-10 years. I can hardly remember last week!
While the study shows an association between supplement use and mortality it does not imply cause and effect. At the start of the study, the average age was 62 years. Participants were followed for almost 20 years which means at the end of the study the women were in their 80s. These older women had a greater risk of death because of their age and their greater likelihood of having a serious disease.
It is important to note that after controlling for all sorts of measures, iron was the only supplement that showed a positive association with mortality. This is consistent with past research (for more information, refer to the NIH’s fact sheet under Current Issues and Controversies about Iron). Taking an iron supplement either in a multi-nutrient formulation or as an individual nutrient increases the probability of mortality in elderly women. While most standard multi-vitamin & mineral formulations contain iron, VitaMedica has never included this mineral in our formulation. Iron-containing supplements should only be taken after lab tests show an iron deficiency. This is because iron overload is twice as common as iron deficiency. Iron supplements should also be taken separately from a multi-vitamin as iron interferes with the absorption of other nutrients.
A few supplements like vitamin B6 and folic acid showed a slightly higher risk of death when dietary and lifestyle factors were controlled. However, nutrients such as the B-complex did not show higher risk. Numerous studies indicate that the ideal way to obtain micronutrients is to stay away from high doses of singular nutrients and supplement with a broader range of nutrients at more modest levels.
VitaMedica’s products are formulated using this approach. Importantly, as new research emerges, our formulations are updated accordingly. Over the past 10 years, we have reduced the amount of carotenoids, vitamin C, and vitamin E in our products. At the same time, we have increased the amount of vitamin D.
Arguably, the best way to obtain micronutrients is from fruits and vegetables and other foods. However, as national health statistics document, fewer than 12% of adults eat the recommended number of servings of fruits and vegetables. In fact, in the 2010 Dietary Guidelines for Americans, the government outlines key nutrients that Americans are lacking including folate, magnesium, vitamins A, C and K. Certain population groups also fall short on folate, vitamin B12 and iron.
Supplements should not be used on their own to prevent chronic disease. Instead their use in combination with a health promoting lifestyle which includes regular physical exercise, eating a plant based diet, limiting alcohol intake and not smoking, goes a long way toward preventing chronic disease.
Keep in mind that this is just one study and other studies have not shown such dramatic results. In fact, other research shows that taking multivitamins reduces or has no effect on mortality. While we will need to wait and see how additional research substantiates or refutes the current study, in the meantime, don’t throw out your supplements!