July 5, 2024 – Neal Barnard, MD, has a very clear message about multivitamins.
“Multivitamins are a commercial product looking for a market,” he said.
But Barnard can understand the reasoning behind multivitamins.
“The idea looks sound: ‘You need certain vitamins and minerals, so let’s throw them all in a pill, and you’re sure you’re going to be OK.' That makes sense for people who may be low in one or another nutrient. But it has significant risks for people who are at risk for being overdosed on a vitamin or a mineral.”
Barnard, an adjunct professor at the George Washington University School of Medicine and Health Sciences in Washington, DC, is co-author of a commentary on a new study that found multivitamins do little to help you live longer and in fact may carry some health risks.
While an estimated 1 in 3 Americans take these supplements, he said that in general, “you’re better off without multivitamins.”
Barnard believes they don’t give us what nature intended.
For example, he said, “vitamin E exists in eight different forms in nature. So, if you eat an almond or a walnut, you’ll get eight different compounds called tocopherols. But if I put them in a multivitamin, I’m not going to put all eight of them in there. I’ll give you one or two. So, you may be messing up the balance that nature had in mind.”
The new large-scale study, which pooled data on three groups of people who were followed for over 20 years, finds that multivitamins did not lower the risk of early death overall, or from heart disease, cancer, or from diseases of the brain's blood vessels. In fact, people who took vitamins daily had a 4% higher all-cause mortality risk than those who didn't take them.
But there are benefits from some specific supplements, a commentary to the study points out. Supplements like beta carotene, vitamins C and E, and zinc were linked to slowing the progression of age-related macular degeneration. Also, in older people, multivitamins were shown to improve memory and slowed declines in thinking skills.
Also, the commentary notes, multivitamins may be a “convenient source” of vitamins, such as B12 and D, that many adults don’t get enough of from food.
The findings of the study echo those of previous studies. In 2022, the U.S. Preventive Services Task Force, an independent, volunteer panel of national experts, looked at some of these other studies and found no connection between multivitamin use and deaths from all causes, cancer, or diseases of the heart and blood vessels. But the task force found insufficient evidence to recommend their use.
Dangers of Multivitamins
Apart from the question of mortality benefit, the impact of multivitamins on health has to be considered, as multivitamins often also include minerals such as iron and copper.
In the commentary on the new study, the authors said iron in multivitamins can have negative effects if users already have enough iron in their diets. Barnard said that hemochromatosis, which can cause liver disease, heart problems, and diabetes, may result from getting too much iron.
Centrum Silver, a common multivitamin supplement, doesn’t have iron, Barnard said. “That’s a good idea, but they should leave it out of all the multivitamins, because nobody should be taking iron unless there’s a specific clinical need for it.”
He also warned against the copper in multivitamin supplements, which he said is linked to Alzheimer’s disease.
Beta carotene, he said, can protect against cancer if it's absorbed from food, but it increases the risk of cancer when ingested in a multivitamin supplement. The evidence for that finding came from a study of smokers and asbestos workers who were at risk of cancer.
John Wong, MD, vice chair of the U.S. Preventive Services Task Force and a professor of medicine at the Tufts University School of Medicine in Boston, said that in light of that study, the task force has recommended against taking beta carotene to reduce the risk of cancer. But he said that the amount of beta carotene found in multivitamins is far lower than the dose used in the study.
Other single vitamins that can be risky, he said, include vitamin A in high doses; vitamin D in high doses, which can cause kidney stones; and vitamin E, which he said carries “some risk for hemorrhagic stroke.” The task force recommends against taking vitamin E.
Where Vitamin Supplements Make Sense
The task force does believe some people with chronic diseases can benefit from particular vitamins.
“This has to do with chronic diseases that can affect the absorption or metabolism of particular vitamins,” Wong said. “Typically, they have to do with nutritional deficiencies that can result from the chronic disease.”
These deficiencies may come from either a disease or a medication, he said. For example, in one kind of pernicious anemia, a rare autoimmune disorder, the body doesn’t absorb vitamin B12.
Jeffrey Kagan, MD, a general internist in Newington, CT, agreed that medications like Prilosec can reduce the ability to absorb vitamin B12, especially if people take them long term for gastroesophageal reflux disease (GERD). When he prescribes one of these drugs to patients with GERD, he urges them to have their B12 levels checked regularly.
Because most Americans have low vitamin D levels, due to not drinking milk and spending too much time indoors, Kagan also suggests that his patients take vitamin D supplements. If their blood tests reveal low levels of protein, he’ll recommend a protein supplement like Ensure that also has many vitamins. For people who are healing from skin wounds, he recommends vitamin C and zinc.
Also, he said, “Someone with cirrhosis, pancreatitis, or Crohn’s disease needs to beef up their vitamins and nutrition.”
But he usually prescribes particular vitamin supplements, not multivitamins, to people who have certain conditions. When people ask him about multivitamins, he said, “My standard answer for the average healthy person is that if you eat a balanced diet with meats, fruits, and vegetables, and you don’t have any special problem, you don’t need multivitamins.”
Eat Right Instead of Taking Supplements
Both the Department of Health and Human Services and the American Heart Association recommend that nutritional needs should be met mostly from nutritious foods and beverages. Wong said that the Preventive Services Task Force agrees with that.
So does Barnard, but he also believes that multivitamins can be harmful in some cases.
That said, targeted supplementation is a very good idea. For instance, vitamin B12 is a substance that people are frequently low on. “But you don’t need to have a cocktail of 15 different micronutrients to get vitamin B12.”
What people should do instead of taking multivitamins, Barnard said, is to look at rebalancing their diets. The typical American diet, he noted, tends to be too low in micronutrients like vitamin C, found in fruit and vegetables, and too high in saturated fat and protein from eating too much meat.
Studies show, he said, that when people shift to better diets, their health improves. “Their weight comes down, their cholesterol and blood pressure go down, and their diabetes improves. Our work, going back 20 years, shows that for some people, diabetes will go away. [Pioneering nutritional researcher] Dean Ornish’s new study shows that early Alzheimer’s disease can improve. Cancer risk can go down, and the cancer trajectory will change for people who already have it.”