Skip to main content

Study Finds No Benefit for Dietary Supplements

Posted on by

Eating healthy
Credit: iStock/Artfully79

More than half of U.S. adults take dietary supplements [1]. I don’t, but some of my family members do. But does popping all of these vitamins, minerals, and other substances really lead to a longer, healthier life? A new nationwide study suggests it doesn’t.

Based on an analysis of survey data gathered from more than 27,000 people over a six-year period, the NIH-funded study found that individuals who reported taking dietary supplements had about the same risk of dying as those who got their nutrients through food. What’s more, the mortality benefits associated with adequate intake of vitamin A, vitamin K, magnesium, zinc, and copper were limited to food consumption.

The study, published in the Annals of Internal Medicine, also uncovered some evidence suggesting that certain supplements might even be harmful to health when taken in excess [2]. For instance, people who took more than 1,000 milligrams of supplemental calcium per day were more likely to die of cancer than those who didn’t.

The researchers, led by Fang Fang Zhang, Tufts University, Boston, were intrigued that so many people take dietary supplements, despite questions about their health benefits. While the overall evidence had suggested no benefits or harms, results of a limited number of studies had suggested that high doses of certain supplements could be harmful in some cases.

To take a broader look, Zhang’s team took advantage of survey data from tens of thousands of U.S. adults, age 20 or older, who had participated in six annual cycles of the National Health and Nutrition Examination Survey (NHANES) between 1999-2000 and 2009-2010. NHANES participants were asked whether they’d used any dietary supplements in the previous 30 days. Those who answered yes were then asked to provide further details on the specific product(s) and how long and often they’d taken them.

Just over half of participants reported use of dietary supplements in the previous 30 days. Nearly 40 percent reported use of multivitamins containing three or more vitamins.

Nutrient intake from foods was also assessed. Each year, the study’s participants were asked to recall what they’d eaten over the last 24 hours. The researchers then used that information to calculate participants’ nutrient intake from food. Those calculations indicated that more than half of the study’s participants had inadequate intake of vitamins D, E, and K, as well as choline and potassium.

Over the course of the study, more than 3,600 of the study’s participants died. Those deaths included 945 attributed to cardiovascular disease and 805 attributed to cancer. The next step was to look for any association between the nutrient intake and the mortality data.

The researchers found the use of dietary supplements had no influence on mortality. People with adequate intake of vitamin A, vitamin K, magnesium, zinc, and copper were less likely to die. However, that relationship only held for nutrient intake from food consumption.

People who reported taking more than 1,000 milligrams of calcium per day were more likely to die of cancer. There was also evidence that people who took supplemental vitamin D at a dose exceeding 10 micrograms (400 IU) per day without a vitamin D deficiency were more likely to die from cancer.

It’s worth noting that the researchers did initially see an association between the use of dietary supplements and a lower risk of death due to all causes. However, those associations vanished when they accounted for other potentially confounding factors.

For example, study participants who reported taking dietary supplements generally had a higher level of education and income. They also tended to enjoy a healthier lifestyle. They ate more nutritious food, were less likely to smoke or drink alcohol, and exercised more. So, it appears that people who take dietary supplements are likely to live a longer and healthier life for reasons that are unrelated to their supplement use.

While the study has some limitations, including the difficulty in distinguishing association from causation, and a reliance on self-reported data, its findings suggest that the regular use of dietary supplements should not be recommended for the general U.S. population. Of course, this doesn’t rule out the possibility that certain subgroups of people, including perhaps those following certain special diets or with known nutritional deficiencies, may benefit.

These findings serve up a reminder that dietary supplements are no substitute for other evidence-based approaches to health maintenance and eating nutritious food. Right now, the best way to live a long and healthy life is to follow the good advice offered by the rigorous and highly objective reviews provided by the U.S. Preventive Services Task Force [3]. Those tend to align with what I hope your parents offered: eat a balanced diet, including plenty of fruits, veggies, and healthy sources of calcium and protein. Don’t smoke. Use alcohol in moderation. Avoid recreational drugs. Get plenty of exercise.

References:

[1] Trends in Dietary Supplement Use Among US Adults From 1999-2012. Kantor ED, Rehm CD, Du M, White E, Giovannucci EL. JAMA. 2016 Oct 11;316(14):1464-1474.

[2] Association among dietary supplement use, nutrient intake, and mortality among U.S. adults. Chen F, Du M, Blumberg JB, Ho Chui KK, Ruan M, Rogers G, Shan Z, Zeng L, Zhang. Ann Intern Med. 2019 Apr 9. [Epub ahead of print].

[3] Vitamin Supplementation to Prevent Cancer and CVD: Preventive Medication. U.S. Preventive Services Task Force, February 2014.

Links:

Office of Dietary Supplements (NIH)

Healthy Eating Plan (National Heart, Lung, and Blood Institute/NIH)

National Health and Nutrition Examination Survey (Centers for Disease Control and Prevention, Atlanta)

U.S. Preventive Services Task Force (Rockville, MD)

Fang Fang Zhang (Tufts University, Boston)

NIH Support: National Institute on Minority Health and Health Disparities

36 Comments

  • Christian Gbekor says:

    What is going to happen to those who are in countries where it’s not possible to go to the lab and check the amount of minerals and vitamins in the body/blood but these dietary/food supplements are at every corner including hospitals and pharmacies with lots of testimonies that they promote good health, heal diseases and prolong life? From Christian Gbekor, Ghana.

  • Emmajene says:

    Taking supplements is the reductionist view of western medicine and the idea that you can continue to eat the standard American diet and remain healthy by taking antioxidant and vitamins and you’ll be healthy. The vitamin /mineral/antioxidant extracted from its whole food form doesn’t work. Case in point- vitamin A and lung cancer. When a study gave beta carotene supplements to people, people actually died from lung cancer, but feed them whole real foods high in beta carotene and lung cancer risk goes way down. Western medicine is greatly missing the boat and would rather rely on drugs and pills when really almost every disease comes from what we expose our genes to, namely FOOD. Eat whole real food. Quit eating the American diet and you’ll live a longer healthier life.

  • LF says:

    I disagree with the assumptions/conclusions made in this article. I have had many patients who were convinced they had Lyme disease only to find that they have a low Vitamin D level. Lab results would say that a Vitamin D level > 30 is not a deficiency; however, the recommended level is 60 to 70. The patients who took the Vitamin D felt better as their levels increased to the 60 range. Also, a Vitamin B12 deficiency is a level around 200; however, patients actually show symptoms less than 400-450. When treated with Vitamin B12, the symptoms improve. Vitamin B12 is difficult to get from the diet in adequate amounts, and even if people were recommended to go outside mostly uncovered without sunscreen, they would still be hard pressed to get adequate amounts of Vitamin D, particularly in the northern states. To publish an article like this is likened to publishing an article that vaccines cause Autism. Now everyone will think that taking vitamins causes cancer. Thank you so much to the author, as now the providers have to field questions about the “cancer-causing vitamins” at future office visits. Might as well rank this one next to the Netflix documentary that states eating bacon is the same as smoking cigarettes! SMH

  • C.P. says:

    The biggest flaw in this study is cited within this article.

    “It’s worth noting that the researchers did initially see an association between the use of dietary supplements and a lower risk of death due to all causes. However, those associations vanished when they accounted for other potentially confounding factors.

    For example, study participants who reported taking dietary supplements generally had a higher level of education and income. They also tended to enjoy a healthier lifestyle. They ate more nutritious food, were less likely to smoke or drink alcohol, and exercised more. So, it appears that people who take dietary supplements are likely to live a longer and healthier life for reasons that are unrelated to their supplement use.”

    Who is to say that supplements don’t make people feel better and have more energy, so that they CAN and DO exercise, and possibly use less alcohol because they feel less stressed? We can’t say that from this study, and those are distinct possibilities.

    Given that this is an epidemiological study, one cannot infer causation, or lack of causation, about supplement use and their effect on health outcomes. It’s too bad that with all of the resources that the US government spends on such studies that our leaders don’t understand such simple basics of medical science and its interpretations, and fund better studies that will actually answer these types of questions.

  • Mallory Annabella says:

    We don’t need vitamins because drugs cure all illnesses, especially when you live off of fast food. Don’t worry because there is always another drug to treat the side effects of another drug. One of my coworkers almost died of heart failure so the doctor prescribed her vitamins and she got better, what a horrible doctor! Sigh!

  • ATP says:

    I’d do my own study because these are all bs. Supplements work if the consumer does. They are no magic pill. Set the McNuggets down and pick up a dumbbell or go for a jog. Supplement – “something that completes or enhances something else when added to it ” add a healthy diet and some exercise to it and leave the “study” by some Dr that would pump you full of FDA approved painkillers and Chemo in a heart beat to make his $$ alone. I can show you amazing body transformations that supplements have helped. Oh btw CBD/Cannabis medicine works too.

  • 1 2

Leave a Comment