Niacin, also known as vitamin B-3 has a number of effects on the body. One of the reasons people take niacin supplements is to increase the levels of HDL cholesterol, also known as "good" cholesterol, in the body. Niacin works by changing the way the body makes these different kinds of cholesterol.
Lipoproteins
In order to understand how niacin increases HDL cholesterol, you need to understand how HDL cholesterol is made. HDL stands for high-density lipoprotein, and it is made by the liver. Three types of lipoproteins are important for your heart health: high-density lipoprotein, low-density lipoprotein and very-low-density lipoprotein, also known as HDL, LDL and VLDL, respectively. The latter two lipoproteins are associated with an increased risk of developing heart disease. Lipoproteins can be distinguished both by the types of lipids they carry and by the proteins present on the surface of the lipoprotein.
Niacin and HDL
Niacin works by reducing the breakdown of HDL cholesterol particles. As a 2008 article in the "American Journal of Cardiology" explains, niacin reduces the destruction of a protein known as apo A-I. Apo A-I is needed to make high-density lipoprotein molecules; by reducing the rate at which this protein is broken down, niacin can increase the amount of HDL in your blood stream. The article also states that niacin may do this by blocking a protein known as β-chain adenosine triphosphate synthase, which is needed for HDL breakdown.
Other Effects
Niacin also affects the activity of cells in the immune system known as macrophages. When niacin is metabolized in the body, it gets converted into a chemical known as a prostaglandin, LipidCenter.com explains. Prostaglandins are important for the immune system and can stimulate macrophages to pull cholesterol out of the walls of the arteries. These macrophages then transfer the cholesterol to HDL molecules, so not only are there more HDL molecules, but cholesterol is more easily transferred into them.
Side Effects
Because niacin works by changing the way the liver handles cholesterol, niacin can potentially damage the liver. This can cause abdominal pain, yellowing of the eyes and skin and dark urine, Drugs.com notes. The prostaglandin metabolite of niacin also causes blood vessels to dilate. This is what causes the flushing and feeling of warmth under the skin that occurs when taking niacin. You should avoid taking niacin if you have severe kidney or liver disease.
