Many supplements for “men’s health” have vague and unsubstantiated claims to efficacy. Among the products I’ve reviewed in the past as “testosterone” boosters, I often saw ingredients that I knew had little or even negative effects on testosterone, based on the scientific literature.
That’s one of the reasons I decided to sit down and write this short article about Green Tea and testosterone. It is not intended to dissuade people from taking Green Tea Extract (GTE), which has a number of anti-obesity benefits. Rather, this article was written to let people know what the science actually says about GTE and hormones.
✲ Only one study purported to have any positive effect on testosterone levels–and only in albino rats.
✲ Other studies, however, described GTE as “castrative” for its efficiency in lowering testosterone.
✲ What little scientific research does exist on human hormone levels suggests that GTE lowers testosterone.
There is no shortage of animal studies involving popular herbal medicines; the main problem is finding studies that are testing for the same variable as the herbal medicine is marketed for. In this case, there are numerous supposed uses of GTE, but few clinical trials examining those exact uses.
With testosterone, I found one study that claimed to find “higher than normal” levels of testosterone in laboratory animals given green tea. But their publicly available data don’t describe what “normal” is, how much the testosterone increased, and they didn’t use a control group.
Another study wanted to determine only the implications on sperm health; this limited outcome scope gave them clearer parameters, a sign of a good study. Their results, interestingly, showed better sperm health, but completely unchanged testosterone levels.
Finally, we have a study which found negative results for both sperm health and testosterone levels. This is the report that said Green Tea has a “castrative effect.” Researchers saw lower sperm counts, less sperm motility, and lower testosterone.
Before we close, we have the only representation of humans involved in GTE studies for testosterone. This review of extant scientific literature was carried out on behalf of researchers working with Polycystic Ovary Syndrome. In reviewing the literature for the anti-inflammatory effects of Green Tea, they inadvertently found another statistical trend: all four human studies found a decrease in testosterone after taking GTE.
No one supplement will interact with everyone’s body the same. That being said, when there is a body of scientific literature pointing to one and only one conclusion, that conclusion can be safely relied upon. It seems that in certains doses (varying for body and animal type), Green Tea Extract has a negative impact on testosterone.
This should not prohibit men from taking GTE, only that consumers should be aware of its effects, especially if it is present in a product marketed to boost testosterone.