Niacin , also known as vitamin B3, is made and used by your body to help convert foods that you eat into the energy you need. However, you can have too much of a good thing—a new study found that high levels of niacin may increase your risk of cardiovascular disease.
The study, published in the journal Nature Medicine, found a breakdown product of niacin, known as 4PY, was strongly linked to the development of heart attack, stroke, and other cardiac events. More specifically, people with elevated levels of 4PY were around 60% more likely, on average, to have these cardiac events compared to people with lower levels. Vitamin D Tablets
“What’s exciting about these results is that this pathway appears to be a previously unrecognized yet significant contributor to the development of cardiovascular disease,” Stanley Hazen, MD, PhD, senior author of the study and Chair of Cardiovascular and Metabolic Sciences at Cleveland Clinic’s Lerner Research Institute, said in a press release. “These insights set the stage for developing new approaches to counteract the effects of this pathway.”
Here’s what you need to know about why niacin can be bad for your heart, as well as expert advice on making sure that your vitamin supplements aren’t putting you at risk.
Our bodies need niacin, and luckily, it’s found in a variety of foods like meat, fish, dairy, and grains, Joseph Daibes, DO, an interventional cardiologist at Northwell Lenox Hill Hospital, told Verywell.
“It plays several key roles, like helping convert food into energy and keeping our skin, nerves, and digestive system healthy,” said Daibes. Niacin also improves circulation and lowers elevated LDL (bad) cholesterol and triglyceride (fat) levels in the blood.
When you don’t get enough niacin in your diet, it can lead to pellagra , said Daibes. The condition can cause mental confusion, weakness, diarrhea, loss of appetite, and other serious symptoms.
“This was a huge issue during the Great Depression, which led the government to mandate that all of the wheat flour and other cereals be fortified with niacin,” said Daibes.
Niacin was also one of the first cholesterol medications out there, according to Daibes. However, researchers noticed a problem: While patients who took niacin did have lower cholesterol, their rates of cardiac events did not decrease—in some people, the rates actually went up compared to people in the general population.
When niacin breaks down, it produces byproducts known as 2PY and 4PY. In the new study, the researchers found that these byproducts, specifically 4PY, have a direct role in triggering vascular inflammation, which damages blood vessels and could contribute to the development of plaque in the arteries (atherosclerosis ) over time—which is a major heart disease risk factor.
“It is well established that inflammation plays a critical role in cardiovascular disease, especially atherosclerotic coronary disease,” said Daibes. Since 2PY and 4PY are pro-inflammatory factors, they increase vascular inflammation, which is directly linked to worse cardiovascular outcomes, such as heart attacks and strokes.
4PY not only triggers inflammation in the cardiovascular system, but can also lead to an increase in plaque accumulation within the walls of arteries, leading to damage to blood vessels, Lena Bakovic, MS, RDN, CNSC, a registered dietitian specializing in chronic disease, weight management, and gut health at Top Nutrition Coaching, told Verywell.
“4PY is thought to trigger cardiovascular inflammation via a newly discovered pathway, which may then increase plaque deposits within artery walls and produce damage to blood vessels,” said Bakovic.
Although the study did not establish direct causation between niacin and an increased risk of heart disease, experts say that larger studies should be done to investigate the possible link.
“This study is a stepping stone for further research that may help us understand how we can further mitigate the risk for cardiovascular disease,” said Daibes.
The fat-soluble vitamins—A, D, E, and K—can be toxic when taken in large doses in supplement form, according to Bakovic. Unlike water-soluble vitamins, these fat-soluble vitamins are stored within the body, and each one comes with its own symptoms of toxicity.
You can get niacin naturally from many different foods, including fish, red meat, poultry, pork, legumes, whole grains, brown rice, nuts, seeds, and bananas, according to Bakovic. It is also added to enriched and fortified foods, such as breads, cereals, and infant formulas.
Niacin is also found in many dietary supplements such as multivitamins or mineral supplements, specifically in the form of nicotinic acid and nicotinamide—two distinct chemical forms of niacin.
In the form of nicotinic acid, niacin is also accessible as a prescription medicine for the treatment of high cholesterol—but do to the potentially dangerous side effects, it’s not as commonly used as it once was.
According to Bakovic, niacin is measured in niacin equivalents (NE); 1 NE is equivalent to 1 milligram (mg) of niacin or 60 mg of tryptophan, an amino acid that the body converts to niacin. The recommended dietary allowance for niacin is generally around 16 mg NE for men and 14 mg NE for women. The allowance is 18 mg NE for women who are pregnant and 17 mg NE for women who are breastfeeding.
“The Tolerable Upper Intake Level, which is the maximum daily intake unlikely to cause harmful effects, is 35 milligrams or 35 NE of niacin” for people 19 years or older, said Bakovic. “Anything beyond that amount poses a risk for toxicity.”
Consuming high doses of niacin in supplement form, particularly going over 500 mg and especially in the form of nicotinic acid, can increase the risk of niacin toxicity, according to Bakovic. One of the more common symptoms of excessive niacin is flushed or red skin, which shows up throughout the body.
Other symptoms of niacin toxicity include gout, digestive issues, nausea, diarrhea, headaches, blurred vision, fatigue, low blood pressure, vomiting, easy bruising, increased bleeding from wounds, and in rare cases, inflammation of the liver.
However, you should know that it’s unlikely you’ll get dangerously high doses of niacin from eating too many niacin-rich foods because dietary sources typically provide well-balanced amounts of the nutrient. The risk is more from supplements, especially if large amounts are taken over time. That’s why you should always talk to your healthcare provider before starting any kind of vitamin.
While more research is needed to fully understand the link, too much niacin or vitamin B3 could be bad for your heart health. You’re not likely to get too much niacin from your diet, but supplements could pose a risk if you take high doses over an extended time.
National Institutes of Health Office of Dietary Supplements. Niacin: fact sheet for health professionals.
Ferrell M, Wang Z, Anderson JT, et al. A terminal metabolite of niacin promotes vascular inflammation and contributes to cardiovascular disease risk. Nat Med. 2024;30(2):424-434. doi:10.1038/s41591-023-02793-8
Mount Sinai. Vitamin B3 (niacin).
Cleveland Clinic. Cleveland Clinic-led study discovers link between high levels of niacin – a common B Vitamin – and heart disease.
National Library of Medicine: MedlinePlus. Pellagra.
National Library of Medicine: MedlinePlus. Niacin for cholesterol.
Harvard T.H. Chan School of Public Health. Niacin — vitamin B3.
By Alyssa Hui Hui is a health news writer and former TV news reporter. She was the 2020 recipient of the Midwest Broadcast Journalists Association Jack Shelley Award.
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