Adequate intake of certain nutrients is associated with a reduction in all-cause mortality when the nutrient source is foods, but not supplements, according to a study published in Annals of Internal Medicine. There was no association between dietary supplement use and a lower risk of death. In addition, excess calcium intake was linked to an increased risk of cancer death, which the researchers found was associated with supplemental doses of calcium exceeding 1,000 mg/day.
The study used a nationally representative sample comprising data from more than 27,000 U.S. adults aged 20 and older to evaluate the association between dietary supplement use and death from all causes, cardiovascular disease (CVD), and cancer. The researchers assessed whether adequate or excess nutrient intake was associated with death and whether intake from food versus supplement sources had any effect on the associations.
For the association between nutrient intake and the risk of death, the researchers found:
When sources of nutrient intake (food vs. supplement) were evaluated, the researchers found:
In addition, the researchers found that dietary supplements had no effect on the risk of death in individuals with low nutrient intake. Instead, the team found indications that use of vitamin D supplements by individuals with no sign of vitamin D deficiency may be associated with an increased risk of death from all causes including cancer. Further research on this potential connection is needed.
The authors note some limitations, including the duration of dietary supplement use studied. In addition, prevalence and dosage of dietary supplement use was self-reported and so is subject to recall bias.