According to 2016 consumer survey data, 71 percent of U.S. adults take some type of dietary supplement. And the appeal of supplements is obvious. We know vitamins are necessary for health, so why not make sure we’re covering our bases?
The darker side of dietary supplements is that many of the alleged health benefits are coming straight from people who stand to make big money from vitamin sales, and the research doesn’t always agree with the claims of vitamin manufacturers and retailers. Here’s a look at four vitamins you may want to think twice about.
1. Vitamin E
According to the National Institutes of Health, the recommended daily allowance (RDA) of vitamin E for adults is 15 mg (or 22.4 IU). RDAs are based on what will meet the nutritional needs of 97-98 percent of healthy people, but supplements are widely available from 200 to 1000 IU per pill. When it comes to vitamin E, the research is clear that you can have too much of a good thing.
A large review of the research by John Hopkins University found that people who took more than 400 IU daily faced a 4-6 percent increased risk of death. Another large study found that, despite health claims to the contrary, vitamin E did not decrease prostate cancer risk in study participants. In fact, men who supplemented with vitamin E were slightly more likely to develop prostate cancer than men who didn’t use the supplement.
2. Vitamin C
Pricey vitamin C supplements marketed for the prevention and treatment of the common cold and the flu have popped up in every grocery store and drug store. They come as pills, lozenges, and powdered drinks and typically contain 500-1000mg of vitamin C, at least 5-10 times the RDA of vitamin C for adults. Some people use supplements daily to prevent colds, and others use high doses at the beginning of a cold to shorten its duration. But a review of the evidence shows that vitamin C only impacts the common cold in one way – if you’re already taking daily vitamin C, your colds may be a little bit shorter. Despite the claims of manufacturers, people who supplement daily don’t get fewer colds, and starting supplementation at the beginning of a cold doesn’t affect cold symptoms. If you choose to take a daily vitamin C supplement to shorten your colds, keep in mind that mega doses can contribute to kidney stones.
3. Vitamin A
Vitamin A can be toxic in large doses, causing symptoms like nausea, vomiting, and abdominal pain. Most cases of vitamin A toxicity occur in adults using mega doses of vitamins to treat illness or in children who accidentally ingest supplements, but researchers are now wondering if smaller supplemental doses of vitamin A can cause health problems too. The RDA for vitamin A for adults is 700-900 mcg, and an article published in The American Journal for Clinical Nutrition notes that just twice this amount has been connected to osteoporosis and hip fracture in people without other symptoms of toxicity.
Seventy-five percent of Americans who take supplements take a multivitamin, making it the most popular dietary supplement in the US. Multivitamins are all different, but most contain a long list of vitamins and minerals, sometimes in amounts well over their recommended daily intakes. Over the last few years, study after study has challenged the alleged health benefits of multivitamins, but there have also been a few that show some health benefit. In a large study of older women, multivitamin use was associated with increased mortality.
An eight-year study showed no protective effect against cardiovascular disease or mental decline but a slight protective effect against cataracts and cancer. And most recently, a 2016 study has contradicted previous research by showing a slight benefit for heart health. The research surrounding multivitamin supplements isn’t clear-cut, and it’s possible that not all adults benefit from them.
It’s important to consult with your doctor before taking a new supplement and to know that adding more fruits and vegetables to your diet is the most evidence-supported intervention you can make for your own health. Fruits and veggies can lower your risk of cardiovascular disease, cancer, diabetes, and high blood pressure without any dangerous side effects. And a cart full of produce is much more affordable than a cabinet full of supplements.
This article first appeared on AskDrManny.com.