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I stumbled on some interesting research that links niacin, HDL levels, vasodilation, and nitric oxide. This is important because it offers a link between heart disease, ED, and ED treatments.

This is strictly for science types who want to learn more about the science of ED. Here’s the research, from Kuvin et al (Am Heart J. 2002;144:165-172):

The study was designed to see what effect it would have on vasodilation (blood vessel relaxation) to increase HDL levels (the “good” cholesterol). This is of interest (to me) because poor vasodilation is considered the cause of much ED, and drugs like Viagra work by increasing vasodilation.

So…the investigators gave patients with coronary artery disease – who have blood vessel problems – niacin (see picture above) to raise their HDL levels. The result was that HDL increased and the blood vessels improved. In patients with no HDL increase, there was no blood vessel improvement.

Next, they exposed human blood vessel cells to HDL, and found that this increased nitric oxide synthase, an enzyme that produces nitric oxide (NO) from L-arginine (note that I have other posts about taking L-arginine, which is available on-line and at any drug store). Part of the physiological process of erection involves the parasympathetic nervous system causing the release of NO in the corpus cavernosum of the penis. NO binds to the receptors of the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation (vasodilation) in the corpus cavernosum, resulting in increased inflow of blood and an erection.

The study started with a niacin dose of 375 mg and worked up to 1500 mg. The niacin used was the prescription drug Niaspan (an extended release form of the drug).

There are several points to consider here:

1. LDL-cholesterol appears to lower nitric oxide, while HDL raises it. Many men with ED also have HIGH LDL and LOW HDL. The point of this study was that even men with low LDL (such as those taking statins) but with low HDL still will have blood vessel problems, but these can be addressed through niacin therapy.

2. This is the first study I’ve seen that offers a rationale for using niacin to help ED (although this is my interpretation – this is not what the study authors are saying).

3. For those who are interested in taking niacin, the effective dose should be closer to 1500 mg, which can be hard to take (because of flushing). Some sex pills on the Internet include niacin as an ingredient, but the dose – usually between 20 and 40 mg – is equal to that found in a typical multivitamin and has no benefit.

4. For those who are considering taking niacin, DO NOT take the non-prescription long-acting niacin formulation found in drug stores. This has been shown to cause liver damage, and should be taken off the market. Take either regular niacin (sometimes called immediate release or IR) or prescription niacin (Niaspan). The IR version causes more flushing, although I found I can tolerate 100 mg after a few days.

If you would like to read the abstract of this study, here it is on Pubmed: