Men over the centuries have noticed that their libido, their desire for sex, tends to wane with age. Probably loss of sexual desire in men has more to do with disease than anything else. Diabetes, hemochromatosis, hypothyroidism, hyperthyroidism, Guillan-Barre disease, cancer, cancer treatment, and many medications rob men of sexual desire, as does weight gain. Fat cells produce estrogen, and estrogen in men kills desire for sex.

There are a number of simple, practical, natural therapies that help restore the male sex drive. Here are just a few.

• The over-the-counter herbal product chrysalin, derived, appropriately enough, from the passionflower, preserves the testosterone a man's body already makes. Since it preserves testosterone rather than stimulating the testes to make more testosterone, chrysalin will not aggravate or cause prostate disease.
• Men with waning sex drives should avoid saw palmetto. This mildly estrogenic herb is great for the prostate but takes away erectile strength. Use pygeum instead.
• In Germany, urologists frequently diagnose a condition called "beer drinker's droop." The hops in beer are mildly estrogenic. They also encourage the growth of belly fat, which makes estrogen. Don't drink beer if you want to restore your sexual ardor. Wine is OK, but whiskey is also estrogenic.
• In general, most "tough guy" drinks, such as whiskey, stimulate estrogen production.
• Androstenedione is scienfically demonstrated to elevate testosterone levels--in women. It may stimulate testosterone production and sexual desire in men over 50, if taken in doses of under 300 milligrams a day. Doses over 500 milligrams a day may have the paradoxical effect of lowering sex drive.
• Androstenediol definitely stimulates testosterone production in men, but only for a short time. Avoid if it you have prostate problems.
• A man's body can turn DHEA into testosterone. There's no need to take more than the recommended dose, since the amount of testosterone the male body can make from DHEA is limited.
• Tribulus terrestris contains a plant chemical, protodioscine, that a man's body can convert into DHEA and then into testosterone. It is helpful in most men with loss of libido, but it's no miracle cure.
• Marijuana contains the same estrogenic compounds as hops. Smoking weed will dent sexual desire, although it may also lift sexual inhibition.