Three mistaken assumptions about dietary supplements to watch out for

Americans seem to have quite a positive view of dietary supplements. According to a 2023 survey, 74% of US adults take vitamins, prebiotics and the like.

The business of supplements is booming, and with all the hype around them, it’s easy to forget what they actually are: substances that can powerfully affect the body and your health, yet aren’t regulated like drugs are. They’re regulated more like food.

Thanks in large part to a 1994 law, the Food and Drug Administration is essentially toothless when it comes to supplements. As the agency acknowledges: “FDA does not have the authority to approve dietary supplements before they are marketed. Companies can sell supplements without going through any sort of approval process, or even having to share safety evidence.”

As a research faculty member in graduate medical education, I’m responsible for teaching resident physicians how to understand and critically engage with health research. I also write about health, wellness and supplements for a broader audience. As a result, I spend a lot of time thinking about supplements.

It’s important to consider why so many people believe supplements can help them lead a healthier life. While there are many reasons, how supplements are marketed is undeniably an important one. In my years following the industry, I’ve found that three mistaken assumptions appear over and over in supplement marketing.

1. The appeal to nature fallacy

The appeal to nature fallacy occurs when you assume that because something is “natural” it must be good. The word natural is used a lot in the marketing of supplements. In the context of health, it often feels right to want natural medicine, remedies, prevention techniques and so forth.

For example, if I say “vitamin C,” what do you immediately think of? Probably oranges or citrus in general and flu prevention. But if I say “the flu shot,” what immediately comes to mind? Probably doctor’s offices, a little bit of pain and pharmaceutical companies.

One of these is clinically proven to prevent flu infections and lessen the severity of illness. The other has been marketed as though it does those same things, but there’s no clinical evidence to support this.

The supplement industry is awash with brand names that incorporate the word “nature,” invoking the appeal to nature fallacy. Also, look at websites and advertisements that urge customers to forgo “artificial” products in favor of “pure” and “natural nutrition”.

Using the word artificial to describe other products and natural to describe a specific supplement is intended to make you feel like that product will be superior to the competition and that you need it to be healthy.

To be clear, “natural” does not equate to “better,” but that’s what the marketing wants you to think.

2. Belief that more of a good thing is better

There’s another assumption that piggybacks on the appeal to nature fallacy: If something is natural, it must be good, and more of it must also always be better. If a little vitamin C is good for us, then a lot of it must be great!

The truth is that our bodies tightly regulate levels of the vitamins and minerals we consume. If you don’t have a deficiency, consuming more of a particular vitamin or mineral through a supplement won’t necessarily lead to health benefits. That’s why supplement skeptics sometimes say, “You’re just paying for expensive pee” – since your body will excrete the excess.

For an example of the more-is-better myth, look at basically any vitamin C supplement. The packaging often prominently displays dosages that can reach 750 or 1,000 milligrams. But adults need only about 75 to 120 milligrams of vitamin C per day. Similarly, look at vitamin D supplements that can come in dosages of 5,000 IU, or international units – a fact also often prominently displayed on packaging. But adults should have no more than 4,000 IU daily. Again, it’s easy to exceed what we need.

3. The action bias

Finally, the supplement industry likes to capitalise on the idea that doing something is better than doing nothing. This is the action bias. Taking action makes people feel like they have more control of a situation, which is especially powerful when it comes to health. “Even if I don’t need the extra vitamin C,” they might think, “I’ll take it just to be sure. What’s the harm?”

The examples in the last section show that supplements often contain many times the recommended daily intake of a particular vitamin or mineral. This assumes that taking that much of any of those particular substances is safe.

It is possible to have too much of a good thing. Too much vitamin C can lead to diarrhea, nausea, stomach cramps and more. Too much vitamin D can lead to conditions including nausea, vomiting and kidney stones. Supplements can also interact with prescribed medications.

For example, St. John’s wort is famous for interacting with contraceptives, immunosuppressive drugs, statins and chemotherapy by exacerbating or dulling their effects. When it comes to supplements, taking them isn’t necessarily better than not.

Be on the lookout for these marketing messages – they aren’t necessarily correct or good for your health. And talk with your doctor before taking any supplements.

Katie Suleta is a doctorate in Health Sciences candidate, George Washington University.

This article was first published on The Conversation.