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30.10.2010


Tea supplement boosts testosterone levels in animal study

Epicatechin
Three polyphenols found in tea raise the testosterone production of male rats, according to a study that researchers at the National Yang-Ming University, Taiwan, published in the Journal of Cellular Biochemistry. Epicatechin [structural formula below] is especially interesting.

The few studies on the hormonal effects of tea cause us, whingeing compilers of this hated web-magazine, to frown. According to a Sri Lankan animal study, a minimal amount of black tea raises testosterone production. [J Ethnopharmacol. 2008 Aug 13;118(3):373-7.] A Polish epidemiological study claims that green tea reduces estradiol production [Br J Nutr. 2006 May;95(5):989-95.] and Unilever research experiments showed that black tea reduced cortisol production after a stressful event minimally. [Psychopharmacology (Berl). 2007 Jan;190(1):81-9.]

Then again, there are test-tube studies in which high concentrations of the polyphenols in tea 200 micromols inhibit the production of testosterone in the Leydig cells. [Asian J Androl. 2009 May; 11(3): 362-70.] At this dose, EGCG in particular is an active inhibitor, epicatechin the opposite.

The Taiwanese did their experiments on rats, not cells. What's more, they experimented with much lower concentrations than the discoverers of the testosterone-inhibiting effects of phenols. The researchers put the rats on a drip containing 1 microgram EGCG, catechin or epicatechin per kg bodyweight and observed that these caused a rise in the testosterone level.

The figure below shows the effect of epicatechin over an 8-hour period. The other phenols had a similar effect. The lower figure shows the effect of the combination of hCG and epicatechin. Tea phenols enhance the effect of hCG.


Tea supplement boosts testosterone levels in animal study

Tea supplement boosts testosterone levels in animal study


When the researchers exposed LH-producing cells from the rats' pituitary gland to GnRH and tea phenols, they saw that epicatechin boosted the GnRH stimulus to produce LH. In test-tube studies, the same epicatechin also enhanced the conversion of androstenedione into testosterone by the testes.


Tea supplement boosts testosterone levels in animal study

Tea supplement boosts testosterone levels in animal study


The researchers discovered that tea phenols, and epicatechin in particular, work via cAMP, a molecule that mediates between receptors and the cell. More cAMP usually means a stronger response to a hormone in this case the response of the pituitary to GnRH and the Leydig cells to LH.

Source:
J Cell Biochem. 2010 May 15; 110(2): 333-42.

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