Having vitamin deficiencies can harm your health, but consuming too much of them can also hurt you — specifically, your heart.
Researchers with the Cleveland Clinic found having high levels of niacin, also called vitamin B3, is strongly associated with a higher chance of developing heart attack, stroke and other adverse cardiac events.
The findings, published in Nature Medicine on Monday, were the result of large-scale clinical studies that found highly circulating levels of 4PY, a breakdown product of excess niacin, directly triggered vascular inflammation, which can damage blood vessels and, over time, lead to atherosclerosis — the build-up of cholesterol plaque in and on artery walls .
Niacin is a common vitamin found in many foods, including meat, fish, nuts, grains and cereals, according to the National Institutes of Health. Eating these foods allows most Americans to consume enough of the vitamin, especially because niacin fortification in "staple foods" like flour and oats has been mandated in the U.S. since the 1940s to prevent deficiency-related health effects, the study noted.
But even though niacin deficiency is a rarity in the U.S., some people do take it as a dietary supplement or as a prescription, particularly those who don't eat enough iron-rich foods and those who use it to treat high cholesterol.
Doctors remove football-sized heart tumor; the patient is now thriving
According to Northwestern Medicine, primary heart tumors affect less than 0.02% of the population.
The study, however, found this supplementation might not be necessary for anyone.
The research team's leader, Dr. Stanley Hazen, said 1 in 4 subjects in the study were found to be getting too much niacin, and, therefore had high levels of 4PY and a higher risk of cardiovascular disease development.
"The main takeaway is not that we should cut out our entire intake of niacin — that's not a realistic approach," Dr. Hazen said. "Given these findings, a discussion over whether a continued mandate of flour and cereal fortification with niacin in the U.S. could be warranted."
The researcher also said those taking niacin for the cholesterol-lowering effects would find better treatments elsewhere, as previous research has shown niacin to be less effective than other cholesterol-lowering treatments and linked it to other negative effects and higher mortality rates.
The doctors note more long-term studies are needed to determine the full effect of chronically high levels of 4PY and what the limit should be for the average person. But Hazen notes the findings do offer a path to potential new treatments or medications to reduce or prevent vascular inflammation and major cardiovascular events.
Hazen added that anyone taking over-the-counter niacin supplements should consult a doctor before continuing its use. Instead, he recommends people focus on diets rich in fruits and vegetables and avoid excess carbohydrates to maintain healthy niacin levels.
