There are valid concerns about the safety of long-term treatment with testosterone particularly with respect to the cardiovascular system and the potential for stimulating prostate cancer development. There are no convincing hard data, however, to support these concerns. If anything, the data strongly suggest that adequate testosterone availability is cardioprotective and coronary risk factors such as diabetes, obesity and the metabolic syndrome are associated with reduced testosterone levels. It is certainly appropriate to avoid giving testosterone to men with prostate or breast cancer but it is not appropriate to accuse testosterone of inducing the development of de novo prostate cancers since evidence for this accusation is lacking (Wang et al 2004; Feneley and Carruthers 2006).
Finally, we looked at the proprietary blends of our remaining boosters, and dug into their ingredient lists. Supplements frequently include ingredients known for their “folk-lore” value; they’re believed to work, even when there isn’t any scientific background to prove it. Though we didn’t ding points if an ingredient wasn’t proven to be good (just so long as it wasn’t proven to be bad), we didn’t want to include any ingredient with evidence of causing harm.
Interest in testosterone began when farmers of old first noticed that castrated animals were more docile than their intact peers. Ditto for castrated humans. For human males with intact gonads, testosterone increases during puberty. It deepens the voice, increases muscle growth, promotes facial and body hair, and spurs the sex drive. Testosterone also is associated with personality traits related to power and dominance.
Barbara Mintzes, at the University of British Columbia, said in a Skype interview, "Androgel was approved for a real condition—men who have a number of clinical or acquired conditions that affect testosterone, either through the testes or pituitary gland. So testosterone replacement therapy makes sense, and producing it in a gel makes sense. Where there is an actual need for the product, there's nothing wrong with that." But, she added, "When this gets marketed for what is essentially healthy aging, the antennas go up."
D-Aspartic acid is a natural amino acid involved in the synthesis and release of testosterone, which research shows can be used as a testosterone booster for infertile men. One 90-day study gave D-Aspartic acid to men with impaired sperm production, and found their sperm count rose from 8.2 million sperm per ml to 16.5 million sperm per ml, more than a 100 per cent increase.
Only a few natural testosterone boosters are supported by scientific studies. The herb with the most research behind it is called ashwagandha. One study tested the effects of this herb on infertile men and found a 17% increase in testosterone levels and a 167% increase in sperm count. In healthy men, ashwagandha increased levels by 15%. Another study found it lowered cortisol by around 25%, which may also aid testosterone.
Testosterone is a steroid from the androstane class containing a keto and hydroxyl groups at the three and seventeen positions respectively. It is biosynthesized in several steps from cholesterol and is converted in the liver to inactive metabolites. It exerts its action through binding to and activation of the androgen receptor. In humans and most other vertebrates, testosterone is secreted primarily by the testicles of males and, to a lesser extent, the ovaries of females. On average, in adult males, levels of testosterone are about 7 to 8 times as great as in adult females. As the metabolism of testosterone in males is more pronounced, the daily production is about 20 times greater in men. Females are also more sensitive to the hormone.