For the general population, taking dietary supplements does not reduce the mortality risk from either cardiovascular disease (CVD) or cancer, a large cohort study concludes.

“People should aim for achieving adequate nutrition through a healthy balanced diet rather than relying on supplements,” lead author Fang Fang Zhang, MD, PhD, Tufts University, Boston, Massachusetts, told Medscape Medical News in an email.

One exception was taking a supplement of lycopene, which did appear to reduce the mortality risk from both CVD and cancer.

However, the study also found that taking a supplement could be detrimental: taking high-dose calcium supplements appeared to increase the risk of dying from cancer.

The study was published online earlier this week in the Annals of Internal Medicine.

In the study, dietary supplement use in the previous 30 days was analyzed among 30,899 adults who participated in six cycles of the National Health and Nutrition Examination Surveys (NHANES) from 1999 to 2000 and to 2009 to 2010.

Nutrient intake from foods and supplements was also analyzed from 27,725 participants who provided one or two valid, 24-hour diet recall information.

The team categorized nutrient intake as being either “inadequate” — defined as levels of total nutrient intake from food and supplements below the estimated average requirement — or as “adequate” when nutrient intake were at levels specified in the Dietary Reference Intakes. Excess nutrient intake was determined by comparing participants’ intake with levels above the Tolerable Upper Intake level.

Study participants who reported taking dietary supplements had a mean age of was 50.7 years, while the mean age of those who did not take dietary supplements was 42.8 years (P < .001).

“More than half of participants (51.2%) reported use of dietary supplements in the previous 30 days, and 38.3% reported use of MVM (multivitamin and mineral) supplements,” Zhang and colleagues observe.

The most commonly used vitamin supplements included vitamin C (used by 40.3% of participants), vitamin E (used by 38.6%), and vitamin D (used by 37.6%).

The most commonly used mineral supplements were calcium (used by 38.6%), zinc (34.5%), and magnesium (33.3%).

In general, participants who took supplements had higher levels of total nutrient intake for all 25 nutrients assessed compared with nonusers. Even when the nutrient intake from supplement use was discounted, they still had higher nutrient intake levels from foods for 23 nutrients compared with non-supplement users, the researchers point out.

Interestingly, however, over half of all participants had inadequate intake of vitamin D, vitamin E, choline, vitamin K, and potassium. Fewer than 5% of all respondents consumed what investigators determined was “excess” intake for all nutrients except niacin.

“During a median follow-up of 6.1 years, 3616 deaths occurred, including 945 CVD deaths and 805 cancer deaths,” the researchers report.

After multivariable adjustment, no dietary supplement except lycopene was associated with a lower mortality risk. Lycopene lowered the risk for all-cause mortality by 18% and death from cancer by 54%.

Importantly, excess intake of calcium was associated with a 62% higher risk of dying from cancer. This risk was confined to high-dose calcium supplements of 1000 mg/day or more, and not to calcium intake from food, the team notes.

At the same time, investigators also noted that vitamin D supplementation at doses in excess of 10 mcg/day — or about 400 IU/day — was associated with an increased risk of both all-cause and cancer mortality.

However, this effect was only seen in participants with adequate vitamin D levels, defined as a serum 25-hydroxyvitamin D level of 50 nmol/L or higher, and not in participants with serum 25-hydroxyvitamin D levels of less than 50 nmol/L.

“Thus, vitamin D supplement use at 400 IU/day or higher may have untoward effects among those with no sign of low vitamin D status,” Zhang observed.

“For those with low vitamin D status, vitamin D supplements had no benefit or harm,” she added.


REFERENCE:  Chen et al: Association Among Dietary Supplement Use, Nutrient Intake, and Mortality Among U.S. Adults: A Cohort Study;