Niacin, also known as vitamin B3 or nicotinic acid, is an important nutrient involved in energy production and healthy skin. Historically, niacin has been recognized for its influence on cardiovascular health. It was considered a treatment for abnormal lipid levels, such as high cholesterol, and widely used to manage and prevent heart disease.
How Niacin Affects Cholesterol Levels
Niacin impacts lipid profiles, including LDL (“bad”) cholesterol, HDL (“good”) cholesterol, and triglycerides. It inhibits the release of fatty acids from fat tissues. These fatty acids are precursors for triglyceride synthesis in the liver. By reducing fatty acid availability, niacin decreases the production of triglycerides and very-low-density lipoprotein (VLDL) particles, which are then converted into LDL cholesterol.
Niacin increases high-density lipoprotein (HDL) cholesterol by a different mechanism. It reduces the breakdown rate of HDL-apo AI, a protein component of HDL, leading to a longer lifespan for HDL particles and increasing their levels. Additionally, niacin can selectively increase specific cardioprotective HDL subfractions.
Niacin’s Evolving Role in Clinical Trials
Niacin has been investigated in large-scale clinical trials to assess its impact on cardiovascular events. The Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides: Impact on Global Health Outcomes (AIM-HIGH) trial examined niacin’s effectiveness in patients with established cardiovascular disease already taking statins. Despite niacin improving lipid profiles, the trial concluded that adding extended-release niacin did not reduce major cardiovascular events like heart attacks or strokes.
The Heart Protection Study 2—Treatment of HDL to Reduce the Incidence of Vascular Events (HPS2-THRIVE) trial explored the benefits of extended-release niacin combined with laropiprant in high-risk patients on statin therapy. It also found no additional reduction in major vascular events compared to statin therapy alone. HPS2-THRIVE reported an increase in serious adverse events, including disturbances in diabetes control, new-onset diabetes, gastrointestinal and musculoskeletal issues, skin problems, infection, and bleeding. These outcomes indicated that the risks of routine niacin administration in optimally statin-treated patients outweighed any potential benefits.
Current Place in Heart Disease Management
The medical consensus regarding niacin’s role in heart disease management has shifted based on major clinical trials. Current guidelines indicate that adding niacin to statin therapy does not improve cardiovascular outcomes in patients already receiving optimal statin treatment. Statins remain the primary and most effective lipid-lowering treatment for reducing the risk of heart attack and stroke.
Niacin is generally not recommended as an add-on therapy for most patients already taking statins. Its use may be considered in specific situations, such as for individuals with severe hypertriglyceridemia, mixed dyslipidemia, or statin intolerance where other therapies are not suitable. Such decisions are typically made by specialized clinicians.
Managing Niacin’s Side Effects
Niacin is associated with several common side effects, primarily the “niacin flush.” This reaction, characterized by redness, warmth, tingling, and itching, occurs due to the release of prostaglandins. It can be uncomfortable and is more pronounced with immediate-release formulations or when first starting treatment.
To mitigate flushing, starting with a low dose and gradually increasing it over several weeks is recommended. Taking niacin with food can also help reduce the intensity of the flush. Extended-release formulations release the vitamin more slowly, lessening flushing severity compared to immediate-release forms.
Other potential side effects include gastrointestinal upset like nausea, vomiting, and diarrhea. More serious concerns involve liver problems, especially with high doses, and an increased risk of elevated blood sugar, particularly in individuals with diabetes. Regular monitoring of liver function and blood glucose is advised when taking niacin.