Niacin has long been used to lower triglycerides and to increase high-density lipoprotein (HDL) cholesterol. This "good" cholesterol helps remove low-density lipoprotein (LDL) cholesterol, the "bad" cholesterol, from the bloodstream.

But niacin isn't for everyone. People who take niacin in addition to common cholesterol medications see very little additional benefit. And niacin can cause uncomfortable and sometimes dangerous side effects.

Niacin (nicotinic acid) is a B vitamin that's used by the body to turn food into energy. Niacin also helps keep the nervous system, digestive system and skin healthy. That's why niacin is often a part of a daily multivitamin, though most people get enough niacin from the food they eat.

When it's used as a treatment to improve cholesterol numbers or correct a vitamin deficiency, niacin is sold in higher doses available by prescription.

Niacin is also available as an over-the-counter supplement. Supplements are not regulated like prescription medications. The ingredients, formulations and effects of over-the-counter niacin can vary widely.

Don't take niacin without discussing it with your health care provider first because niacin can cause serious side effects when taken in high doses.

Niacin can lower triglycerides by 25% and raise HDL cholesterol by more than 30%.

Triglyceride levels over 150 milligrams per deciliter (mg/dL) or 1.7 millimoles per liter (mmol/L) have been associated with a higher risk of heart disease.

The risk of heart disease is also increased in men who have HDL levels below 40 mg/dL (1.0 mmol/L) and in women who have HDL levels below 50 mg/dL (1.3 mmol/L).

There's currently some debate about the exact role HDL plays in the body and in the development of heart disease. But HDL has generally been thought to pick up excess bad cholesterol in the blood and take it to the liver for disposal, which is why HDL is dubbed the good cholesterol.

Despite niacin's ability to lower triglycerides and raise HDL, research suggests that niacin therapy isn't linked to lower rates of death, heart attack or stroke.

High doses of niacin available via prescription can cause:

• Severe skin flushing combined with dizziness
• Rapid heartbeat
• Itching
• Nausea, vomiting and diarrhea
• Gout
• Liver damage
• Diabetes

In the past, it was thought that HDL levels would increase even more if niacin were added to cholesterol-lowering medications called statins, such as atorvastatin (Lipitor) and simvastatin (Zocor). But newer studies indicate that niacin provides little additional benefit when compared with statins alone.

However, niacin may be helpful in people who can't tolerate statins or other cholesterol-lowering medications. Some studies suggest that people with high triglycerides and low HDL cholesterol may benefit from niacin.

Lifestyle changes are helpful in boosting HDL:

• Stop smoking if you're a smoker.
• Eat a healthy diet.
• Exercise regularly.
• Avoid consuming trans fats or partially hydrogenated oils.