Vitamin T for Sex
Hot, hot hormones.
Behavior Drives Hormones, Not Vice Versa
For argument's sake, let's suppose that for every smidgen of a decline in
testosterone, there was a proportional decline in sexual drive, energy, and
libido, while for every smidgen of a rise, there was an increase. If that were
the case, researchers should be able to select a group of normal, healthy guys
for a study, measure their testosterone levels, and show that the men with the
higher testosterone levels are more libidinous, sexually active, or more
Indeed, some studies have suggested such a correlation. But there turns out
to be a confounding factor: Acting aggressively and having sex both
raise testosterone levels, so the correlation seems due to behavior driving the
hormones, rather than the other way around. This phenomenon has been discussed
in many leading texts on the subject.
When experiments control for those factors -- acting aggressively and having
sex -- the vast majority of studies, whether of humans or animals, show that
individual differences in testosterone levels across the normal range don't
particularly predict individual differences in aggressiveness or sexual
activity. My own study, "Testicular function, social rank, and personality
among wild baboons," published in the journal
Psychoneuroendocrinology (Vol. 16, No. 4, 1991), is among the many to
have found this.
A Mere 15% of Normal Is Enough
Here is the critical point: Give Sullivan replacement testosterone so that
his circulating levels return to 15% of normal, 100% of normal, or 150% of
normal, and you will have roughly the same effect in all cases. The best
single review on this subject is "Behavioral effects on androgens in
humans," published in the August 1996 issue of the American Journal of
Psychiatry. Over a very wide range, testosterone has pretty much the same
effect on behavior. Push levels below that range (due to castration or any of a
number of diseases), and physiology and behavior change. Push levels above that
range, by abusing anabolic steroids, and you'll typically boost aggression,
perhaps libido as well. But within that broad range -- from 15% to 150% of
normal -- behavior and libido remain roughly the same.
Increases Body Mass, Not Sex Drive
So what CAN extra testosterone do? A few studies, including one in the
October 1992 issue of the Journal of Clinical Endocrinological
Metabolism, have shown that boosting testosterone levels in aged males
increases body mass and decreases cholesterol levels. Sullivan, who experienced
a 20-pound weight gain, can now squat more than 400 pounds and feels a surge of
energy "less edgy than a double espresso but just as powerful."
However, there have been no double-blind studies showing that supplemental
testosterone reinstates "youthful" sexual performance or libido,
alertness, or energy.
And the testosterone experts agree. Consider the following summary from a
recent review published in the July 2000 issue of the journal
Geriatrics: "Hormones such as DHEA, human growth hormone, and
testosterone tend to decline with aging, but the therapeutic value of
[restoring] them to 'normal' physiologic levels has not been substantiated by
controlled clinical trials." Furthermore, Williams' Textbook of
Endocrinology (1998, 9th edition), essentially the "bible" of the
field, states that "The decline in male sexual function with age does not
appear to be endocrine-mediated."