The research, published April 9 in the Annals of Internal Medicine, found that adequate intake of certain nutrients was associated with a reduced risk of death by any cause, but the benefit was only present if those nutrients were consumed in food sources. When those same nutrients were taken in the form of a supplement, the lower risk of death disappeared. The study used a nationally representative sample composed of data from more than 27,000 U.S. adults age 20 and older to evaluate the association between dietary supplement use and death from all causes, as well as deaths specifically from cardiovascular disease and cancer. The data were collected as part of the National Health and Nutrition Examination Survey between 1999 and 2010. The individuals participating in the study were asked if they had used any vitamins, minerals, or other dietary supplements in the previous 30 days. If they had, they were asked to produce the supplement containers, or recall the details from memory. Participants also reported how much of each supplement they took and how often. Participants were interviewed twice about what they had to eat and drink in the previous 24 hours, from which the researchers modeled the participants’ usual diets and usual dietary intake of nutrients, using a method developed by the National Cancer Institute known as the NCI method. (The daily dietary interviews allow the researchers to extrapolate what the expected nutritional content of each person’s diet would be.) More than half the participants had used supplements in the prior 30 days. Compared with people who didn’t take supplements, supplement users were: older, more likely to be female, less likely to be smokers or heavy drinkers, and more likely to have a comorbid condition at the start of the study (these conditions included cancer, heart disease, stroke, high cholesterol, hypertension, and diabetes). The individuals analyzed for this study were followed for a median of 6.1 years after the supplement and dietary data were collected. Deaths during those follow-up periods were recorded. For the association between nutrient intake and the risk of death, the researchers found:
Adequate intakes of vitamin K and magnesium were associated with a lower risk of death.Adequate intakes of vitamin A, vitamin K, and zinc were associated with a lower risk of death from a cardiovascular event.Excess intake of calcium was associated with higher risk of death from cancer.
When sources of nutrient intake (either via diet or via supplement) were evaluated, the researchers found:
The lower risk of death associated with adequate nutrient intakes of vitamin K and magnesium only existed when those nutrients came from foods, and disappeared when they were from supplements.The lower risk of death from cardiovascular events associated with adequate intakes of vitamin A, vitamin K, and zinc was limited to nutrients from foods, and disappeared when nutrients came from supplements.Calcium intake from supplement totals of at least 1,000 milligrams per day was associated with increased risk of death from cancer, but there was no association for calcium intake from foods.
The Data Suggest Getting the Nutrients You Need From Food Is Better Than Taking Supplements, but if You’re Deficient to Begin With, It May Be a Different Story
The findings from this research suggest that there may be benefits to getting the vitamins and nutrients your body needs from a healthy diet — and that these benefits may disappear if you get those nutrients from supplements, explains the senior author of the study, Fang Fang Zhang, MD, PhD, an associate professor at the Friedman School of Nutrition Science and Policy at Tufts University in Boston. “One thing that is clear (from these results) is that dietary supplement use is not a substitute for a healthy balanced diet,” she says. It’s important to note, however, that this research didn’t look at certain subgroups who may have different nutritional needs from those of the general population, Dr. Zhang adds. Certain subgroups are probably more likely to benefit from supplements, she says. “These may include individuals with nutritional deficiency or specific nutritional needs, such as pregnant women, people with medical conditions that affect their ability to absorb adequate nutrients from foods, or those with specific dietary practices, such as vegetarians.” And the new findings do not necessarily suggest that those people don’t benefit from supplements. But if you’re a healthy person with no vitamin or mineral deficiencies, the findings do suggest you may not benefit from taking supplements, Zhang says. Nutrients from food are generally better than supplements, unless you are deficient, says Elizabeth Bradley, MD, the director of the Center for Functional Medicine at Cleveland Clinic in Ohio. Dr. Bradley was not involved in this research. But if someone is deficient (in iron or vitamin D, for example), he or she may still benefit from taking a supplement to be sure they are getting an adequate intake each day, she says. “It’s more important to work with your physician or nutritionist to understand what you might be deficient in,” Bradley adds. For people who have been sick or have undergone medical treatment, there may be nutritional deficits that take a very long time to address through diet alone. “That would be a targeted reason to take a supplement,” she says. She suggests discussing your supplement use with your doctor. “People shouldn’t just start taking supplements without any particular reason or testing,” she adds. “Not everyone needs to take a multivitamin every day.”
There Were Limitations to This Study
It’s important to note that this was an observational study, and that’s one of its limitations, Bradley says. The study shows there’s an association between getting the nutrients you need via diet and more health benefits (compared with getting the nutrients you need via supplements). But the results don’t necessarily prove that it’s the intake through supplements versus the intake through diet that’s causing those health benefits to disappear, she explains. “Whenever there is an observational study, especially in regard to nutrition and supplements, there are so many confounding variables.” The researchers did control for factors like socioeconomic status, education, smoking, physical activity, and chronic health conditions. But there are still factors that may influence supplement use that weren’t accounted for. The people in the study who were supplement users had more comorbid conditions, such as cancer, cardiovascular disease, hypertension, and high cholesterol, than the nonusers of supplements. The researchers did control for the presence of those comorbid conditions. But, Bradley adds: “Is there some inherent bias in which the people who were sicker were more likely to take supplements? Would an individual be motivated to take more supplements if they were already sicker?” These factors could have contributed to mortality associations for some of the supplement users. The study is also limited by self-report bias (when research participants may respond in a way that makes them look as good as possible). In this case, people might have exaggerated the amount or kinds of nutritious food they consumed and left out some of their less-healthy food choices. The bottom line, according to Bradley, is that this research should raise questions about the value of some supplements for otherwise healthy individuals. But it shouldn’t be taken to mean that everyone should stop taking supplements entirely. And as always, if you have questions or concerns about the health value of a specific supplement you’re taking or considering taking, you should talk to your doctor.
