From the book Testosterone: A Man's Guide http://smile.amazon.com/Testosterone...tosterone+book
Supplements That Claim to Improve Sexual
Function and/or Testosterone
Many people either don’t trust big drug companies or they prefer the idea of using products that they see as “natural” or “herbal”. Therefore I’m going to address a few of these. Please keep in mind a general rule about supplements: They are not regulated by the FDA. Most companies make a lot of unsubstantiated claims as long as they have a tiny sentence on their label that says “this statement has not been reviewed by the FDA”. Lack of regulation leads to a wide range in potency of the product between manufacturers (one reason it can make some studies hard to verify). ConsumerLabs.org is a good resource since they test supplements to determine who is lying about their ingredients, but you need to have a paid subscription to the site.
Testosterone prohormones such as androstenedione, androstenediol, and dehydroepiandrosterone (DHEA) have been heavily marketed as testosterone-enhancing and muscle-building nutritional supplements for the past decade. Concerns over the safety of prohormone supplement use prompted the United States Food and Drug Administration to call for a ban on androstenedione sales, and Congress passed the Anabolic Steroid Control Act of 2004, which classifies androstenedione and 17 other steroids as controlled substances. As of January 2005, these substances cannot be sold without prescription. Contrary to marketing claims, research to date indicates that the use of prohormone nutritional supplements (DHEA, androstenedione, androstenediol, and other steroid hormone supplements) does not produce either anabolic or ergogenic effects in men.
Korean red ginseng
Two double-blind, placebo-controlled trials, involving a total of about
135 people found evidence that Korean red ginseng may improve erectile function when compared with placebo. A dose of 900 mg was given three times daily and the study period was 8 weeks.
In an analysis combining the results of six controlled trials, researchers
found some evidence supporting the benefits of Korean red ginseng. There are doubts about this conclusion as these studies were small size and non- validated.
L-arginine is an amino acid with many functions in the body. One of these is its role in the production of nitric oxide which helps relax blood vessels. This relaxation is essential in the development of an erection. Drugs like Viagra increase the body’s sensitivity to the natural rise in nitric oxide that occurs when we get sexually excited. Another approach might be to raise nitric oxide levels, which led to the idea of trying L-arginine.
Oral arginine supplements may increase nitric oxide levels in the penis and elsewhere. The main data that generated some interest in the use of arginine for erectile dysfunction came from a small double-blind trial in which 50 men with erectile dysfunction received either 5 g of L-arginine or placebo daily for six weeks (NOTE: a capsule contains 500 mg, so 10 capsules a day!). More men in the treated group experienced improvement in sexual performance than in the placebo group. However, a double-blind crossover study of 32 men found no benefit with 1,500 mg of arginine given daily for 17 days. The significant difference in dose and shorter course of treatment may explain the discrepancy between these two trials.
L-arginine has been advertised as “natural Viagra” but there is little evidence that it works. Drugs based on raising nitric oxide levels in the penis have not worked out for pharmaceutical developers; the body seems to adjust to the higher levels and maintain the same level of response.
Arginine supplementation appears to work only in those whose erectile dysfunction is due to low nitric oxide levels. In other words, arginine would be unlikely to help those whose decreased libido is due to factors other than low NO levels. Remember, erectile dysfunction is a complex syndrome and may be due to many different factors, both chemical and psychological.
NOTE: Large doses of L-arginine can activate the herpes virus in those who have been exposed to it. You may want to take medication for herpes treatment if you decide to use this supplement. L-arginine is also commonly used in bodybuilding supplements since it can cause transient increases in growth hormone.
Yohimbine and yohimbe
Yohimbine HCl is an indole alkaloid found in the bark of the Pausinystalia yohimbe tree. Yohimbe bark has been used in Africa for centuries as an aphrodisiac. It is available as a supplement but is also available by prescription in the United States under the trade-name Yocon. It too helps with erections by relaxing blood vessels in the penis.
Yohimbine has been studied in combination with L-arginine. One study of 45 men found that one-time use of this combination therapy an hour or two before intercourse improved erectile function in those with only moderate erectile dysfunction. Arginine and yohimbine were both taken at a dose of 6 g, which would require a lot of capsules (if taken in powder form a tea spoon has 5 g). All the related studies were very small. I doubt that there are future larger studies planned since we now have effective erectile dysfunction drugs that work.
NOTE: Yohimbine (and yohimbe) present a number of safety risks related to increased heart rate, blood pressure, insomnia, anxiety, and liver/ kidney dysfunction. It is best to use this under physician supervision.
Carnitine is a compound that helps transport fatty acids for the generation of metabolic energy. In addition to its apparent benefit for diabetes, the heart and affecting bone mass it may have benefit with erectile dysfunction. Propionyl-l-carnitine at 2 g/day plus acetyl-l-carnitine also at 2 g/day and testosterone (testosterone undecanoate 160 mg/week) were separately compared with placebo. The results indicated that both carnitine and testosterone improved erectile function; however, while testosterone significantly increased prostate volume, carnitine did not. Other studies seem to indicate that propionyl-l-carnitine at 2 g/day enhanced the effectiveness of sildenafil (Viagra) in a small group of men with diabetes who were not responding to sildenafil on at least eight occasions.
Zinc is a trace mineral that is second only to iron in the body. Zinc is involved in many physiological processes in the body such as wound repair, proper functioning of the immune system, cell division, cell growth, proper taste and smell sensation. This important mineral also plays a role in the proper metabolism of carbohydrates and for normal childhood growth and sexual development. Men who are deficient in zinc may have an issue with fertility and libido, while women who are deficient in zinc may have an upset menstrual cycle.
Severe zinc deficiency is known to negatively affect sexual function. Since marginal zinc deficiency is relatively common, it is logical to suppose that supplementation with zinc may be helpful for some men. This hypothesis has only been studied in men receiving kidney dialysis but the results were promising. You can take too much zinc, so check with your doctor about how much is enough.
NOTE: I take 50 mg of zinc plus 3 mg of copper a day to support my immune system. Zinc can lower copper, which is also important for the immune system. I take a product made by Jarrow that combines the two. But zinc does not increase testosterone, but can help support testosterone production.
The herb maca (Lepidium meyenii) is another supplement advertised as “herbal Viagra.” In one study of rats, maca enhanced male sexual function. For those of you who aren’t rats, there is one published human trial. In this small, 12-week, double-blind, placebo-controlled study, use of maca at 1,500 mg or 3,000 mg increased male sexual desire but no data was shown on the quality of erections. The claims that it increases testosterone have not been substantiated with data.
Tribulus terrestris L. (Zygophyllaceae) have been used as an aphrodisiac both in the Indian and Chinese traditional systems of medicine. Administration of Tribulus terrestris extract (TT) increased sexual behavior and intracavernous pressure both in normal and castrated rats and these effects were probably due to the androgen increasing property of TT.
In a study done in Bulgaria, twenty-one healthy young 20–36 years old men were randomly separated into three groups—two experimental (each n = 7) and a control (placebo) one (n = 7). The experimental groups were named TT1 and TT2 and the subjects were assigned to consume 20 and 10 mg/kg body weight per day of Tribulus terrestris extract, respectively, separated into three daily intakes for 4 weeks. No changes in testosterone, androstenedione and luteinizing hormone blood levels were observed with either dose.
There are other herbs that have been promoted as improving sexual function in men. Among these are Ashwagandha, Avena sativa (oat straw), eleutherococcus (the so-called Siberian ginseng), L-citrulline, Macuna pruriens, molybdenum, muira puama or potency wood (you have to love the name), pygeum, Polypodium vulgare, Rhodiola rosea, saw palmetto, schisandra, suma, traditional Chinese herbal medicine, and deer or antelope velvet antle. There are no well-designed, controlled scientific studies that support any of those claims.
Many herbal supplements that claim to improve sexual function have been found to contain Viagra or Cialis purchased in China at cheaper prices. The FDA has stopped those companies from selling them but many keep reappearing in the unregulated supplement market.
All supplements that actually increase testosterone, such as androstenedione, are considered performance-enhancing drugs. They have been banned in the United States. This is just as well as they only increased testosterone for a few hours and had the potential to cause liver problems. New supplements keep appearing on the market and claim to increase the body’s production of testosterone or growth hormone. Be very skeptical about those claims and do not waste your money on them!
The best and safest way to supplement your testosterone is to use approved products under your physician’s supervision and care.