Cholesterol is the raw material the body uses to make testosterone and all other steroid hormones. So, goes the reasoning of some in the strength sports world, a diet that is high in cholesterol keeps your testosterone level up. The more cholesterol you eat, the more testosterone you produce. But animal studies show the opposite to be the case.
The indications that a cholesterol-rich diet is unhealthy are not very strong. Every egg yolk the average person eats raises their chance of a heart attack by 2 percent, according to epidemiological studies. [Am J Clin Nutr. 2001 May;73(5):885-91.] That’s nothing. Other epidemiological studies have also found a higher risk of cancer among people who eat large amounts of egg yolk – the most important source of cholesterol in our diet – but the relationships were probably the result of pollution and not cholesterol. [Am J Clin Nutr. 2004 Jul;80(1):58-63.]
There is, however, a condition doctors call hypercholesterolemia. In most active and healthy people there is no clear relationship between cholesterol intake via food and the concentration of cholesterol in the blood. Of course some people are thriftier with their cholesterol than others, and they are more likely to develop hypercholesterolemia if they eat too much cholesterol.
Hypercholesterolemia is not only a health risk, but animal studies have shown that it also lowers testosterone levels. [Endocr Res. 2001 Feb-May; 27(1-2): 109-17.] Mice with a raised cholesterol level produce less testosterone if they are given hCG injections. [J Nanosci Nanotechnol. 2005 Aug; 5(8): 1273-6.]
By the way, there are human studies in which strength athletes produce more testosterone the more cholesterol they consume. Apparently they had a healthy cholesterol level. [J Appl Physiol. 1997 Jan;82(1):49-54.]
Researchers at the University of Jaen in Spain will soon publish the results of an animal study, which may reveal something of the mechanism through which hypercholesterolemia lowers testosterone levels. The Spaniards believe there is a link with the renin-angiotensin system [RAS].
The RAS is intended to mitigate the effects of low blood pressure. When blood pressure is low, this system makes sure that small amounts of the active hormone angiotensin I are converted into the more active angiotensin II. Angiotensin gets the blood vessels to contract so that blood pressure rises.
In the testes the enzyme aspartylaminopeptidase [ASAP] converts angiotensin II into angiotensin III. The enzymes aminopeptidase-N [APN] and aminopeptidase-B [APB] convert angiotensin III into angiotensin IV.
The Spaniards gave male mice feed that contained 1 percent cholesterol. The mice’s cholesterol level rose, their testosterone level went down.