Writing in Life Extension - A Practical Scientific Approach, Durk Pearson and Sandy Shaw indicate how the sex flush described by Masters and Johnson (blushing in face, neck, shoulders, chest etc.) is caused by histamine release. The histamine release caused by taking niacin on an empty stomach results in a similar flushing effect. This is harmless, and only lasts a few minutes. Pearson and Shaw say in their book that they take niacin fifteen to thirty minutes before sex to enhance the natural sex flush.
Owing to the slower nature of sexual arousal in heterosexual erotic wrestling, the use of niacin may be a worthwhile experiment for some. Incidentally this vitamin is excellent for lowering blood pressure and cholesterol problems. It is not frequently supported by the establishment because it is very cheap and is out of patent and therefore there is little profit to be made from it.
Anyone interested in vitamins for extending lifespan is well advised to read the best selling book, Life Extension - A Practical Scientific Approach which you can obtain from Amazon.com - see GeoCities' home page.
Also see The Life Extension Foundation's web pages, click on banner right for the index page.