A new study reveals connections between niacin and heart disease. Led by researchers at Cleveland Clinic, the study found that the B vitamin produces a by-product called 4PY that is strongly associated with vascular inflammation and heart disease risks. Preclinical trials showed an even stronger connection, showing that 4PY directly triggered the inflammation, damaging blood vessels and leading to atherosclerosis over time.

Cleveland Clinic. Cleveland Clinic-Led Study Discovers Link between High Levels of Niacin - a Common B Vitamin - and Heart Disease. February 19, 2024.

Yu-Ming Ni, MD, a board-certified cardiologist and lipidologist at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in Fountain Valley, California, says he views the findings as a “nail in the coffin,” to how doctors should think about niacin. While he adds that many doctors have been wary about niacin for years, the study adds new insight into just how dangerous the substance can be.

Historical studies on niacin benefits may be out-of-date

In an old study on niacin, the vitamin has been thought to have some benefits to heart health, such as potentially reducing the risks for heart disease, Dr. Ni says. However, subsequent studies have not always confirmed these benefits —and researchers have learned more and more about the side effects of the vitamin as time has gone on, he adds.

Office of dietary supplements - niacin.

“For a while, a lot of cardiologists were prescribing niacin for cardiovascular prevention as a result of that early trial,” Dr. Ni explains. “We encountered a couple problems – more recent studies didn't show much of a benefit—and this medication has significant side effects.”

These side effects include things like flushing, difficulty tolerating hot showers, increased blood sugar levels, insulin resistance, and dizziness, and have caused some cardiologists like himself to be skeptical about niacin for years.

Should doctors discourage all niacin intake?

Niacin can be taken in many forms, including prescription medications, over-the-counter medications or supplements, and in the diet. Given the recent study, Dr. Ni recommends encouraging patients to avoid niacin medications and not writing unnecessary prescriptions. When it comes to diet, however, he says the advice is less clear.

Because niacin-rich foods—which include liver, chicken, and salmon—come with other nutrients, it may be harmful to cut these out of a diet, Dr. Ni says. However, it is important to remind patients that eating too much of one vitamin via food or supplementation can have negative side effects and that you should encourage variety in their food choices.

Office of dietary supplements - niacin.