More on niacin: No flush, no good.

Several readers wrote in wanting to know more about why we don't recommend no-flush niacin products. A little bit of background will help us explain.

The term niacin comes from nicotinic acid vitamin, but it's used to refer to both nicotinic acid and a closely related molecule, nicotinamide. Both nicotinic acid and nicotinamide are necessary to prevent pellagra, a disease that causes skin inflammation, diarrhea, and dementia. After they were first discovered in the 1930s, nicotinic acid and nicotinamide were known for a time as the pellagra-preventing vitamins.

In the mid-1950s, researchers discovered that nicotinic acid -- but not nicotinamide -- was remarkably effective at lowering cholesterol and triglyceride levels. We talk about niacin having these good effects, partly because niacin appears on ingredient and nutrition labels, but strictly speaking, it's just nicotinic acid that does.

Nicotinic acid -- but again, not nicotinamide -- also triggers the release of prostaglandins that cause flushing, a more severe and sometimes uncomfortable form of the blushing that occurs when we're embarrassed. So researchers have looked for ways to chemically package nicotinic acid so it retains its ...