Niacin, or vitamin B-3, is a supplement known for its ability to lower cholesterol and prevent heart disease. There are three major forms of niacin available on the market: nicotinic acid, nicotinamide, and inositol hexaniacinate. All of these forms of niacin are available over-the-counter, either by itself or included in a multivitamin, in varying amounts.
Nicotinic acid is the form of niacin most researched for its ability to lower cholesterol. In fact, nicotinic acid has been shown to affect all aspects of your lipid profile: it can raise high-density lipoproteins ( “good” cholesterol, HDL ) and lower low-density lipoproteins ( “bad” cholesterol, LDL ) and triglycerides.
Although nicotinic acid affects all parts of your lipid profile, it is also noted for its nasty side effects, which include itching, flushing and hot flashes. These side effects can be intolerable and are the most common reason nicotinic acid use is discontinued.
Flush-free or no-flush niacin is a form of nicotinic acid also known as inositol hexaniacinate. Flush-free niacin gets its name from its ability to alleviate side effects like flushing that are seen with other forms of niacin. Unfortunately, there really isn’t a lot known about flush-free niacin, and researchers are finding that its active form may not even enter the blood. Therefore, it is unlikely that flush-free niacin lowers cholesterol.
Flush-free niacin consists of six niacin molecules connected together by the chemical inositol. It is proposed that, in the body, this chemical is broken down into nicotinic acid and enters the bloodstream. Since it this process takes longer time to occur, it is thought that this is the cause for its diminished side effects. However, if a high amount of flush-free niacin is ingested, you may still feel the side effects of niacin.
Flush-free niacin is able to dilate blood vessels and has been used the treatment of diseases, such as Raynaud’s disease. Experiments using nicotinic acid are plentiful; however, studies examining the effectiveness of inositol hexaniacinate alone in lowering cholesterol levels are few.
In fact, there has been some debate as to whether or not flush-free niacin lowers cholesterol levels -- there have not been enough studies to support or deny this. One study has indicated that up to 2,400 mg of flush-free niacin each day (in divided doses) is needed to lower cholesterol levels, whereas other studies have indicated that flush-free niacin is ineffective in lowering cholesterol.
One notable study examining different forms of niacin measured the amounts of free nicotinic acid, the niacin that lowers cholesterol, found in the blood after the product was ingested. The study found that after 1.6 grams of inositol hexaniacinate was taken, only 0.6 micromoles/L of nicotinic acid was detected in the blood.
In comparison, taking one gram of the immediate-release nicotinic acid resulted in 240 micromoles/L detected in the blood, while taking two grams of sustained-release nicotinic acid resulted in an average of 31 micromoles/L detected in the blood, both of which are enough to lower cholesterol.
So, with very little nicotinic acid in the blood seen in this study, as well as the lack of evidence seen in other studies, it is doubtful that flush-free niacin is effective in lowering cholesterol.
Sources: Dib JG, Dedeyan S. Purported benefits of niacin niacinate. Am J Health Sys Pharm. 2004;61:307-308. Inositol hexaniacinate. Altern Med Rev. 1998;3:22-223 Meyers CD, Carr MC, Park S, and Brunzell JD. Varying cost and free nicotinic acid content on over-the-counter niacin preparations for dyslipidemia. Ann Intern Med 2003;139:996-1002 Norris RB. Flush-free niacin:dietary supplement may be benefit-free. Prev Cardiol. 2006;9(1):64-65
Dib JG, Dedeyan S. Purported benefits of niacin niacinate. Am J Health Sys Pharm. 2004;61:307-308.
Inositol hexaniacinate. Altern Med Rev. 1998;3:22-223
Meyers CD, Carr MC, Park S, and Brunzell JD. Varying cost and free nicotinic acid content on over-the-counter niacin preparations for dyslipidemia. Ann Intern Med 2003;139:996-1002
Norris RB. Flush-free niacin:dietary supplement may be benefit-free. Prev Cardiol. 2006;9(1):64-65