Ask the Doctors

Dear Doctor: I've been taking niacin for years to lower my cholesterol. Do you think it really helps?

Dear Reader: First, let's look at niacin and its role in the body. Niacin is a B vitamin needed to create compounds crucial to cellular function. A shortage of niacin, or vitamin B3, can lead to diarrhea, nausea, vomiting, rash and, when severe, neurologic conditions that manifest as confusion and dementia. Fortunately, because of our varied and plentiful diet, not to mention food supplementation, niacin deficiency is rare in this country.

Some research does support niacin's ability to improve cholesterol levels. In 1955, in one of the earliest studies of niacin, researchers found that doses of 1,000 to 3,000 milligrams significantly lowered total cholesterol levels in men. Niacin has also been found to lower levels of LDL, the so-called "bad" cholesterol, while raising levels of HDL, the so-called "good" cholesterol.

Niacin has an impact in other ways as well. A 2007 study of 30 patients who took 1,000 milligrams daily showed a reduction in the thickness of their carotid arteries' interior lining and lower levels of CRP (C-reactive protein, a marker of inflammation) when compared to a placebo. Further, a 2009 study of a niacin-plus-statin regimen showed that it led to a reduction in a marker for atherosclerosis in the heart.

Such research suggests that niacin could decrease the risk of heart attacks and strokes. The science, however, is less than conclusive.

A 1986 study followed 1,189 men who had a history of heart attack and compared those who took niacin at 3,000 milligrams per day to those who got a placebo. After five years, the niacin group reported fewer heart attacks, but no difference in the death rate. After 15 years, however, the niacin group reported an 11 percent decrease in mortality rates, mostly from a decrease in heart disease.

Studies of niacin in addition to a statin have not shown benefit against either death rates or heart attacks. A 2011 study in the New England Journal of Medicine assessed the impact of 1,500 milligrams of niacin in addition to the drug simvastatin in those with cardiovascular disease. After three years, the authors found no impact on mortality. A 2014 study in the New England Journal of Medicine echoed these findings, with no benefit after 3.9 years of statin-plus-niacin treatment.

It may be that niacin, when taken with a statin, provides no additional bang for the buck. The significant decrease in heart attacks and strokes seen with statin therapy may overwhelm any potential benefit of niacin. Further, as the 1986 study showed, the benefit of niacin may take up to 15 years to show benefit; the trials of statin-plus-niacin were only for three to four years.

Overall, niacin does seem to have beneficial effects on cholesterol and on reducing atherosclerosis, or hardening of the arteries. However, it's not as powerful as a statin in decreasing rates of heart attacks, and the benefit might not become evident for years.

If you cannot tolerate a statin, niacin may be a good option. But discuss it with your doctor.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

More like Ask the Doctors