The scientists behind the work discovered that adequate intake of vitamin A, vitamin K, magnesium, zinc and copper were associated with a lower risk of premature death, but only when these nutrients came from food. In addition, during a household interview, they answered whether they had used any dietary supplements in the previous 30 days. It's important to note that the study involved self-reported dietary supplement use and dosage, and it's unclear whether specific usage durations may influence the outcome.
The researchers found that taking supplements didn't lower the risk of death during the study follow-up period, while those who got the recommended amount of certain nutrients from foods had a lower risk of death in that time frame. Association between dietary supplement use, nutrient intake, and mortality among United States adults: a cohort study. Those who said they had used supplements were asked for details, including how often they took the products.
The study showed that more than half of the participants of the study had reported using dietary supplements, while 38.3% reported using a multivitamin and mineral supplements.
The new study isn't the first to link supplement use with harmful effects.
This was associated with a 53 per cent greater risk of death from cancer, although the relative risk remained small.
Zinc is present in beans and legumes, resembling lentils and chickpeas.
In individuals who had low levels of nutrient intake, dietary supplements did not affect their mortality risk.
"Our results support the idea that, while supplement use contributes to an increased level of total nutrient intake, there are beneficial associations with nutrients from foods that aren't seen with supplements", Zhang says.
Nutrients sourced from foods were monitored with 24-hour dietary recalls.
Dr. Rekha Kumar, an endocrinologist, wasn't surprised by the finding that people consuming healthy diets lived longer and that supplements didn't seem to extend life.
"I don't think you can undo the effect of a bad diet by taking supplements", said Kumar, an assistant professor of medicine at NewYork-Presbyterian and Weill Cornell Medicine.
'Meanwhile, it is clear diets high in these components are healthy.
"It's more likely to be someone looking for more energy and vitality or trying to treat symptoms such as hair loss or leg cramps", she said.
In 2015, only 12.2 percent of Americans met the recommendations for eating fruit, and just 9.3 percent ate enough vegetables - even though eating enough fruits and vegetables as part of an overall healthy diet reduces the risk of many chronic diseases, including cardiovascular disease, type 2 diabetes, some cancers, and obesity. But there was no link between intake of calcium from food and risk of death from cancer.