Boston, MA—A new study from Tufts University says that nutrient intake is only associated with decreased risk of all-cause mortality when the nutrient source is foods; The study says that there is no association between dietary supplement use and a lower risk of death, and that excess calcium intake is actually linked to an increased risk of cancer death. However, industry experts are already finding issues with the study.
The study in question is titled “Association Among Dietary Supplement Use, Nutrient Intake, and Mortality Among U.S. Adults: A Cohort Study,” by Fan Chen et al., and published in Annals of Internal Medicine. It used data from the National Health and Nutrition Examination Survey (NHANES) from 1999-2010, and cross-referenced participants with mortality data from the National Death Index.
The participants were 30,899 U.S. adults who answered questions on dietary supplement use. The measurements were dietary supplement use in the previous 30 days and nutrient intake from foods and supplements. The results were 3,613 deaths during a median follow-up of 6.1 years, including 945 CVD deaths and 805 cancer deaths.
Having used dietary supplements in the past was not associated with mortality outcomes. Adequate intake of vitamins A and K, magnesium, zinc, and copper was associated with reduced all-cause or CVD mortality, but only when intake was from food. Excess intake of calcium—specifically, supplemental calcium—was associated with increased risk for cancer death.
The limitations noted were that reporting of dietary supplement use is subject to recall bias and that results from observational data may be affected by residual confounding.
Daniel Fabricant, Ph.D., president and CEO of NPA, said in a media statement: “This is fake science and it’s spreading misleading information to the general public. The first line of defense against disease is a balanced healthy lifestyle, and supplements are important for the vast majority of Americans who may not receive the recommended daily nutrients from diet alone.”
The statement noted that poor diet in those already diagnosed with cancer in the past was a major confounder in the study. Participants were more likely to be cancer survivors, smokers, physically inactive, diabetic, and in poor general health.
The statement also pointed out that, even in a sample size of 30,000 people, the trend associating risk of death with number of supplements did not achieve statistical significance. The study itself comes to the conclusion that “Use of dietary supplements is not associated with mortality benefits among U.S. adults,” not that supplements are harmful.
NPA’s statement also mentioned that the use of vitamin E supplements in combination with multivitamins was associated with lower risk of death in the study. This fact was not included in either the press release from Tufts University or the study’s abstract.