Researchers have found that nutrients from food may be linked to lower risks of death, while excess intake of certain supplements may have the opposite effect.
Taking supplements leads to an increased level of total nutrient intake.
Dietary supplements include vitamins, minerals, herbs, amino acids, and enzymes.
Suppliers sell them in different forms, including tablets, capsules, powders, and liquids.
Dietary supplements should not replace complete meals, which are essential to nurturing the body. Talking to healthcare providers before making the decision about whether to take supplements is a good practice. Doctors can help people achieve a balance between nutrients from food and supplements.
Many supplements also contain active ingredients that may have strong biological effects. Any of the following actions could be harmful or even life-threatening: combining supplements, mixing supplements with medicines, or taking too much of some supplements, especially vitamin A, vitamin D, and iron.
When buying supplements in the United States, it is important to read labels and get information about the manufacturer. The Food and Drug Administration (FDA) are responsible for taking action against any adulterated or misbranded supplements — but not before the products are available on the market.
Supplement consumption in the US
According to the 2018 consumer survey conducted by the Council for Responsible Nutrition (CRN), consumer confidence in products and trust in the dietary supplement industry is strong among people in the U.S.
The survey found that 75 percent of U.S. individuals take dietary supplements, as opposed to just 65 percent in 2009.
"This year's data provide further evidence that dietary supplements are mainstays in modern-day health and wellness regimens," explains Brian Wommack, the senior vice president of communications at the CRN.
Vitamin and mineral supplements such as vitamin D and calcium remain the most popular types. However, the use of herbals and botanicals — especially turmeric — has significantly increased during the past 5 years.
The main reason that U.S. individuals take dietary supplements is overall health and wellness, according to the survey.
Nutrients from food vs. supplements
Although many people use dietary supplements, a recent study found that multivitamins, vitamin D, calcium, and vitamin C showed no advantage or added risk in the prevention of cardiovascular disease or premature death.
The team, from the Friedman School of Nutrition Science and Policy at Tufts University in Medford, MA, conducted a study to evaluate the association between dietary supplement use and all-cause mortality. The researchers have published their results in the journal Annals of Internal Medicine.
"As potential benefits and harms of supplement use continue to be studied," points out senior study author Fang Fang Zhang, Ph.D., an associate professor at the Friedman School of Nutrition Science and Policy, "some studies have found associations between excess nutrient intake and adverse outcomes, including increased risk of certain cancers."
The study used data from more than 27,000 U.S. adults and assessed whether adequate or excess nutrient intake was linked to all-cause mortality, and whether results changed if the nutrients came from supplements instead of food.
For each nutrient, the scientists calculated the daily supplement dose by "combining the frequency with the product information for ingredient, the amount of ingredient per serving, and ingredient unit."
They assessed the participants' dietary intake of nutrients from foods using 24-hour dietary recalls and mortality outcomes through the National Death Index through December 31, 2011.
There were several key findings:
- Adequate intakes of vitamin A, K, zinc, and magnesium — from food, not supplements — were linked to a lower risk of death.
- Adequate intakes of vitamin A, vitamin K, and zinc — from foods, not supplements — were associated with a lower risk of death from cardiovascular disease.
- Excess intake of calcium was associated with a higher risk of dying from cancer.
- Excess intake of calcium from supplements (at least 1,000 milligrams per day) was associated with an increased risk of death from cancer.
High intake of some supplements is harmful
In addition to the harmful effects of excess calcium intake from supplements, the researchers found that people with no sign of vitamin D deficiency who use vitamin D supplements may have an increased risk of all-cause mortality.
Further research on this potential connection is necessary.
"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."
Fang Fang Zhang, Ph.D.
Zhang adds that it is important to understand the effect that the nutrient and source might play on health and mortality outcomes — especially if not beneficial.
She also notes some limitations in the study, including the duration of dietary supplement use studied and the fact that dietary supplement use was subject to recall bias.