Are Dietary Supplements Necessary?

From the lecture series: The Skeptic's Guide to Health, Medicine, and the Media

By Roy Benaroch, MD, Emory University

Sales of vitamins and other dietary supplements in the United States total an estimated $25 billion a year. Fish oil sales alone account for over a billion dollars. But are dietary supplements necessary or are we just wasting our money? More importantly, are they safe?

Composition with dietary supplement capsules. Drug pills
(Image: By monticello/Shutterstock)

Popularity of Fish Oil: How Did It Start?

In the United States, fish oil supplements are a $1.2 billion industry. Even though the vast majority of recently published research shows no evidence of health benefits, about 8% of US adults report taking these supplements.

Image of sources of fish oil
(Image: By Africa Studio/Shutterstock)

The fish oil story begins in several remote villages in Northwest Greenland in the 1970s. Two Danish scientists, Hans Olaf Bang and Jorn Dyerberg, had noticed that very few of the Inuit Eskimos living there had heart disease.

Their diet, which consisted mainly of whales, seals, and fish, contained a lot of fat and cholesterol, and the thinking at the time was that these animal fats contributed to cardiovascular risk, yet their hearts stayed healthy.

Bang and Dyerberg hypothesized that it was a certain kind of fat, known as omega-3 fatty acids, that helped protect the heart. These omega-3s are found in abundance in diets that are rich in seafood, especially from oily fish like mackerel and sardines.

Study after study did show that a diet relying on fish was associated with good long-term heart health, and has been confirmed in other populations in many parts of the world.

This is a transcript from the video series The Skeptic’s Guide to Health, Medicine, and the Media. Watch it now, Wondrium.

Eating fish is good for your heart, but consuming a fish-based supplement, like fish oil, is not the same as eating fish.

Does Fish Oil Help Heart Health?

Pharmacies and health food stores started to stock up on fish oil supplements in the 1980s, but it was in the early 2000s that the supplements started to become popular. This popularity was driven by advice from the American Heart Association (AHA), which issued a statement in 2002 that concluded that omega-3 fatty acid supplements reduced the incidence of heart disease.

Even then, the evidence wasn’t great: Observational trials of people taking fish oil supplements showed mixed results. There had been three clinical trials at that time, and two of the three showed modest benefits. But the statement from the AHA was unequivocal, driving advice in the popular media, popular diet books, and from physicians, too.

The 2000s became the decade of fish oil—and not just for heart disease. Here’s a quote from the Chicago Tribune, from 2002: “Fish oils display a remarkable ability to improve health in all ways, even reducing your risk for heart attacks and stroke.”

The article continued that fish oils, “Might improve symptoms of rheumatoid arthritis, eczema, irritable bowel syndrome, Alzheimer’s disease, developmental delay, bipolar disorder, depression, attention deficit disorder, diabetic neuropathy, and age-related macular degeneration.”

All that from one pill.

Here’s a tip: The more unrelated conditions a medicine or supplement claims to treat, the less likely it is to do anything for any of them.

When you read about anything that’s supposed to help with a huge number of different health conditions, be skeptical. Those kinds of claims are often—not always—a marker for either marketing genius or maybe wishful thinking.

Learn more about why fish oil supplements are a $1.2-billion industry

Comparing Fish Oil Claims to Clinical Results

In 2003, a long-term, follow-up study of 3,000 Welsh men was published that should have at least begun to put the brakes on fish oil enthusiasm. These were men who already had heart disease, some of whom were advised to either eat more fish or take fish oil supplements.

In this study, the men who consumed more fish were more likely to die than those who didn’t change their diets, and the group that took fish oil supplements fared even worse.

More studies like that one followed over the next decade. In 2012, a large meta-analysis of 14 high-quality clinical trials involving a total of over 20,000 patients concluded that purified fish oil supplements did not help people with heart disease.

Fish Oil capsules on fishing hooks
(Image: By Mincemeat/Shutterstock)

Another analysis showed that 22 of the 24 clinical trials looking at fish oil for heart disease published from 2005 to 2012 showed no benefit.

The recommendations do seem to be shifting, though slowly. The AHA now says that people with heart disease “may want to talk with their doctors” about omega-3 supplements.

In some ways, the popular press may be ahead of these recommendations, publishing articles like “Why You Don’t Need to Take Fish Oil Supplements,” from Men’s Health magazine, or from The New York Times, “Fish Oil Claims Not Supported by Research.”

Still, sales of fish oil supplements don’t seem to be dropping, despite over 15 years of research weighing against their benefit.

Learn more about the reasons for conflicting headlines and stories

What We Can Learn from the Media

What can we learn from the fish oil story? Dietary influences on health are complicated.

Eating fish is healthy, but that doesn’t mean that you can get the same health benefits from eating fish-derived supplements. You can eat vitamin pills that might contain some of the same components of foods, but that’s not the same as eating the foods. This same advice goes for eating fruits and veggies.

In the case of fish oil, we can’t blame the media for prematurely declaring it a healthful supplement—that trend was started by a well-respected nonprofit health organization. But they jumped the gun and the press followed along.

The fish oil story demonstrates how hard it is to replace or revise a story once it’s become popular. The story was that fish oil is good for you, and turning that ship around is going to be much harder than it was to launch the ship in the first place.

Doctors, health organizations, health media, and the general public—we don’t like to change our minds. Once we get an idea, it’s difficult to let go.

Learn more about who suffers from the oversimplification of a “clickbait” headline

Why Vitamins Are Necessary

Fish oil is one example of a food component that fails to deliver the health benefits of the food it comes from. An even bigger example of the same phenomenon may be the broader market of what are called “micronutrients.”

Micronutrients include vitamins, minerals, and other compounds that are present in small amounts in the foods we eat. We know that these micronutrients are essential for health.

Our bodies cannot synthesize vitamins—that is, we can’t make them from scratch—so we have to get them from the foods we eat. In the case of vitamin D, we can also make our own supply of this essential nutrient from sunlight exposure.

In years past, specific vitamin deficiencies were common and led to poor health and death. We know that scurvy, from a vitamin C deficiency, killed more sailors during the age of discovery than people killed during the American Civil War.

Pellagra killed about 100,000 people in the United States, primarily in the southern states, when a change in the way corn was processed in the early 1900s led to widespread niacin deficiency.

But these vitamin deficiencies, with few exceptions, have become very rare in the developed world. We have year-round access to a huge variety of foods, and many of our foods are fortified with added vitamins, just to be sure.

Nonetheless, taking extra vitamins, often in the form of multivitamin tablets with a mix of dozens of micronutrients, remains very popular. Sales of vitamins and similar products in the United States probably total $25 billion a year. But are they doing us any good?

Learn more about how to think like a skeptic when reading news in any medium

Examining Usefulness of Vitamin Supplements

Image of Vitamins supplements as a capsule with fruit vegetables nuts and beans inside
(Image: By Lightspring/Shutterstock)

In this case, when you scan the articles and headlines, the mainstream sites got it right. From Fox News in 2017, a story titled “Do You Really Need These Vitamin Supplements?” summarized several large, key studies.

One from Johns Hopkins found that vitamin E supplements, overall, were associated with a small but measurable increase in death rates; another found that vitamin E supplements increased prostate cancer risk.

The article also pointed out that taking vitamin C doesn’t lessen your chance of getting a cold, and that large studies have shown that those who take multivitamin supplements have an increased mortality.

The article from Johns Hopkins provides direct links to the studies quoted.

The Wall Street Journal has also covered this from a similar angle, in the detailed article “Is it a Good Idea for Adults to Take a Daily Multivitamin?”

The article was far less direct about the evidence against multivitamins. It started with quotes from a physician who recommended multivitamins to his patients, then mentioned one specific study that showed an 8% reduction in cancer risk for vitamin-taking adults.

Further down in the article, point out that though some individual studies show benefits, the majority of high-quality reports do not support the routine use of multivitamins to improve health. Still, the article goes from somewhat pro-vitamin to anti-vitamin and might leave the wrong impression if skimmed or read for only the first few paragraphs.

Although the weight of the evidence does not support the routine use of multivitamins by the vast majority of people in the developed world, some individuals are genuinely at risk for specific deficiencies. They need to be diagnosed and treated.

Iron deficiency is especially prevalent in children and can lead to long-term, even permanent cognitive deficits. There are also specific health conditions that can lead to vitamin B12 or other deficiencies.

Vitamins are important, and all of us should get the vitamins we need to stay healthy. But extra vitamins, for the vast majority of us, do not improve health and may make us unhealthy.

Risks Associated with Vitamin Supplements

When it comes to dietary supplements and vitamins, at least as sold in the United States and Canada, the products are not regulated like medications and there is minimal, if any, oversight into the quality of the products you can buy.

In one study, a third of fish-oil supplements sitting on store shelves had broken down into other kinds of fats that are far less healthful. Products like melatonin, St. John’s wort, and many other herbal supplements often don’t contain what the labels say they do.

A 2013 study reviewing DNA evidence in North American supplements found that only two of 12 products from supplement companies were accurately labeled. The other products contained fillers, including rice and weeds, and many of the products did not even contain the supplement named on the label.

Even if you think supplements might help your health—and certainly some studies of specific supplements show value in some clinical studies—often what you purchase is not what was used in the studies. You also have no practical way of knowing what’s in the bottle.

Common Questions About the Necessity of Dietary Supplements

Q: Why are food supplements necessary?

The necessity of dietary supplements increases depending on our diet. Modern food is grown using methods that strip away natural nutrients, so supplements can give us the extra vitamins and minerals that food or diet cannot. 

Q: What is the best time to take dietary supplements?

Usually, it’s best to take dietary supplements with food to aid in absorption, but ultimately, however, what’s recommended on the label is most likely the optimal way to take a particular supplement.

Q: Do dietary supplements actually do what they claim?

Many studies have shown little to no benefit in taking dietary supplements. Generally, they do no harm, but there have been recorded cases when taking supplements can be detrimental.

Q: Can dietary supplements have side effects?

Dietary supplements can and do have many adverse side effects including but not limited to diarrhea, high blood pressure, and kidney damage. 

This article was updated on December 18, 2020

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