Niacin, a member of the B complex family, has been used for decades to treat high triglycerides and other lipid abnormalities. The term "niacin" is used to describe two nutritionally equivalent compounds -- nicotinic acid and nicotinamide, or niacinamide -- which are converted in your cells to nicotinamide adenine dinucleotide, or NAD. NAD is responsible for most of niacin's metabolic effects. However, only Niaspan -- a controlled-release prescription drug -- and other forms of nicotinic acid are used for treating lipid disorders. "Non-flushing" forms of niacin, such as nicotinamide, are ineffective for this purpose.
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Atherosclerosis, or hardening of the arteries, is the hallmark of coronary artery disease, which is a principal killer of American adults. High triglycerides, low HDL cholesterol and high LDL cholesterol are all risk factors for atherosclerosis. Nicotinic acid lowers triglycerides and LDL cholesterol, and, unlike most other lipid-modifying drugs, effectively increases HDL cholesterol. In fact, according to a May 2003 review in "American Journal of Health-System Pharmacology," Niaspan and other forms of nicotinic acid are the most effective drugs available for increasing HDL cholesterol.
Mechanism
According to scientists at the University of Pennsylvania, nicotinic acid exerts some of its benefits by attaching to a specific cellular receptor, GPR109A, found in your fat tissue. Stimulation of this receptor by Niaspan and similar drugs causes a reduction in the release of fatty acids from fat cells. Since fatty acids are the precursors for triglyceride synthesis, fewer fatty acids result in reduced triglyceride synthesis. As your triglyceride level falls, lipid processing in your liver changes, leading to lower LDL and higher HDL cholesterol levels.
Flushing
GPR109A receptors are also found in your skin and some immune cells. When nicotinic acid stimulates receptors in these cells, they release inflammatory molecules, such as histamines and prostaglandins. As these inflammatory mediators spread, they cause dilation of blood vessels, itching and warmth, all part of the "flush" experienced by people who take nicotinic acid for lipid abnormalities. Because it does not trigger GPR109 receptors, nicotinamide does not cause flushing, but it does not possess the same lipid-modulating properties demonstrated by nicotinic acid.
Considerations
Nicotinic acid is a useful agent for treating lipid abnormalities, particularly high triglyceride and low HDL cholesterol levels. However, its use is associated with a prominent flushing of the skin, which many people find unpleasant. Niaspan is a controlled-release form of nicotinic acid with fewer side effects than immediate-release formulations, but some users still experience an unacceptable amount of flushing with Niaspan. Nicotinamide, a form of niacin that does not cause flushing, is not useful for treating lipid disorders. If your niacin preparation causes unacceptable side effects, talk to your doctor about your options.
References
- "American Journal of Health-System Pharmacy"; Niacin for Dyslipidemia: Considerations in Product Selection: J. McKenney; May 2003
- "The Journal of Clinical Investigation"; Seeing Red: Flushing out Instigators of Niacin-Associated Skin Toxicity; R.L. Dunbar, J.M. Gelfand; August 2010
- "The American Journal of Cardiology"; Mechanism of Action of Niacin; V.S. Kamanna, M.L. Kashyap; April 2008
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