• Posted February 20, 2024

Too Much Niacin May Be Bad for the Heart

Niacin is an essential B vitamin, but new research reveals that too much of it may harm your heart.

Found in many foods that millions of Americans eat, excessive amounts of niacin can trigger inflammation and damage blood vessels, scientists report in the Feb. 19 issue of the journal Nature Medicine.

"The average person should avoid niacin supplements now that we have reason to believe that taking too much niacin can potentially lead to an increased risk of developing cardiovascular disease,"senior study author Dr. Stanley Hazen, chair of cardiovascular and metabolic sciences at the Cleveland Clinic's Lerner Research Institute, told NBC News.

The recommended daily allowance of niacin for men is 16 milligrams per day, while it is 14 milligrams a day for women who are not pregnant, according to the Mayo Clinic.

Ever since the 1940s, when grains and cereals began to be fortified with niacin, Americans have gotten plenty of the vitamin in their diet. The move to fortify those foods was prompted by evidence suggesting that very low levels of niacin could trigger the development of a potentially fatal condition called pellagra, said Hazen, who is also co-section head of preventive cardiology at the Heart, Vascular and Thoracic Institute.

Ironically, niacin supplements were once prescribed by doctors to improve cholesterol levels.

Dr. Amanda Doran, an assistant professor of medicine in the division of cardiovascular medicine at the Vanderbilt University Medical Center in Nashville, Tenn., was surprised to learn that niacin could drive up the risk of heart disease.

"I don't think anyone would have predicted that niacin would have been pro-inflammatory,"she told NBC News. "This is a powerful study because it combines a variety of techniques: clinical data, genetic data and mouse data."

In the new study, Hazen's team first analyzed fasting blood samples from almost 1,200 patients who had come into a cardiology center to be evaluated for heart disease. What did they discover? There was a substance, dubbed 4PY, in some of the blood samples that is only made when there is too much niacin in the body. 

That finding prompted two additional "validation"studies, which included data from a total of just over 3,000 adults who either had heart disease or were suspected of having it. The two studies, one in the United States and one in Europe, showed that 4PY levels predicted the future risk of heart attack, stroke and death.

The final part of the study turned to experiments in mice. When injected with 4PY, inflammation increased in the rodents' blood vessels. 

The results are "fascinating"and "important,"Dr. Robert Rosenson, director of metabolism and lipids for the Mount Sinai Health System in New York City, told NBC News.

Rosenson said he hopes the food industry will "stop using so much niacin in products like bread. This is a case where too much of a good thing can be a bad thing."

The new information could also influence dietary recommendations for niacin, Rosenson added.

The discovery may also lead to new ways to lower blood vessel inflammation, Doran noted.

"It's very exciting and promising,"she said.

More information

Harvard Health has more on niacin and heart disease.

SOURCE: Nature Medicine, Feb 19, 2024; NBC News