Few vegetables have garnered as much attention in health circles as garlic has. Traditional cuisine from around the Mediterranean–from Italy to Spain, from North Africa to the Middle East–has included garlic in many forms. The current trend of garlic as a health supplement has taken this small vegetable from a tasty addition to sauces and oils to a certifiable fad.
In fact, one market estimates that garlic sales of all kinds could exceed $15 Billion by 2029. Of all the health benefits attributed to garlic, perhaps one of the most fascinating is the supposed boost to testosterone. In this article, I’ll dive into the scientific research, and the interesting world of garlic chemistry to find the answers.
✲ Studies are split as to the efficacy of garlic for testosterone, with some indicating big gains, others showing a marked decrease.
✲ The most steady results are that garlic can protect against certain tissue damage, with testosterone effects mixed.
✲ Discrepancies in data may be due to the preparations of garlic, which can result in two wildly different compounds.
✲ Definitive evidence may have to wait until studies of specific compounds against one another can be conducted.
Proof of Testosterone Benefit
Every credible study I could find dealt with laboratory animals (in vivo) or their tissues (in vitro). But that doesn’t necessarily discredit all results. In this case, because all we have are animal studies, we’ll have to extrapolate to human viability.
The study with the most promising results comes from Japanese researchers who published just last year. They used an extract of garlic called S-allyl Cysteine (SAC), and injected it into what’s called the intraperitoneal cavity (the space between organs in the torso) of mice.
After a single administration of SAC, the testicular and plasma testosterone significantly increased in the mice. Furthermore, researchers were able to identify enough cellular activity that they may have found the mechanism for SAC’s activity, namely, that it looks to increase the StAR (steroidogenic acute regulatory) protein motility. (For more on this, read my article on Luteolin and testosterone.)
These results build on earlier Japanese research that garlic powder can increase all hormone activity, including testosterone, associated with protein anabolism (anabolic means “building”).
A third study showing promising results was conducted a few years ago, and used a garlic extract prepared by the researchers. After administration, test animals showed a significant testosterone increase compared to the control group.
Decreases in Testosterone
These results sound pretty promising, but if taken alone wouldn’t tell the whole story. That’s because researchers in the UK, publishing with the prestigious Physiological Society, actually found testosterone decreases after garlic extract was administered. Interestingly, their conclusion was that garlic was not helping the StAR protein, but actually preventing it from carrying out its function.
Additionally, a University researcher I know shared an article with me, whose full data show decreases in testosterone after garlic administration. (The public Abstract of the study is available here. My associate is not authorized to share his research credentials with third-party websites, but he did let me view the full results of the study.)
Explaining the Differences
Whenever we find different results–especially contradictory results–we have to start looking for differences in the studies themselves. Garlic itself presents a few variables to scientists right from the outset, and the preparations of the garlic may be the biggest delineator of success or failure. Depending on how garlic is prepared, two different chemicals are present: S-Allyl Cysteine (SAC) or diallyl thiosulfinate, commonly called Allicin.
Abbreviated to SAC or ACSO depending on the literature, this compound is the predominant biochemical compound in garlic, and has been shown to help with diabetes and liver diseases. This is also the primary compound studied in the first study we discussed, showing the most reliable testosterone gains.
SAC is odorless, as well, and has a light, sweet taste. If that doesn’t sound like the garlic you know, that’s because as soon as garlic is cut, chopped, sliced, or grated, SAC begins to transform into Allicin.
As soon as a garlic cell is ruptured (which is what happens on a molecular level when a knife passes through a clove), the very chemicals in the garlic react defensively. By converting SAC into diallyl thiosulfinate (Allicin), the garlic attempts to stave off whatever just threatened it.
In the case of our garlic grater, Allicin is obviously outmatched. But in the world of cells and chemicals, Allicin may be the most potent plant-protector we’ve yet discovered. That’s because Allicin can out right kill everything from Staph infection cells (MRSA) to cancer cells.
That antimicrobial property is exactly what has made garlic such a pervasive herbal and folklore remedy for everything from infection to, yes, vampirism. Even before people knew what microbe were, they knew that garlic (prepared by dicing or chopping) could kill off bad things.
SAC vs Allicin
Now that we know the basic difference between SAC and Allicin, it’s easy to see why we saw such divergent data from various studies. It appears that SAC helps with cellular activity, while Allicin actively kills cells. Thus, if research is being conducted on testosterone production with garlic which predominantly has Allicin, it’s doubtful much success will be seen.
This becomes especially problematic when we consider that far and away the most common preparations of garlic involve first cutting, chopping, blending, or macerating the tissue.
Some data suggests that aged garlic extract may contain higher amounts of SAC versus Allicin, but that would all depend on the specific preparations and laboratory credentials of the supplier.
A Third Set of Results
Finally, before I conclude, I have a bizarre study that looked at the effects of microwave radiation on testicular tissue and testosterone production. Israeli researchers found (unsurprisingly) that radiation can damage the tissue of testes and diminish testosterone production. They also found, though, that giving the animals garlic extract mitigated that damage.
These data may not benefit anyone in the real world, but I include it for the sake of including all the science known regarding testosterone and garlic. This research may support latter findings in the field, especially in the case of settling the Allicin v. SAC issue.
It appears that garlic may have testosterone boosting properties. It also appears, conversely, that it can decrease testosterone. The best that the literature can present, especially in the words of one of the contradictory studies, is that more research needs to be done. Especially in the case of Allicin versus SAC. As clearly as can be determined right now is that SAC, in the sole study where it has been isolated, does indeed increase testosterone. In all the studies with negative results that I could find, either the preparation was unclear, or resulted in an Allicin-predominant product.
For future research, scientists may look at a three-way, placebo controlled study of the two compounds, together. Presently, consumers and researchers should be aware that two completely different chemicals, with opposite indicatory effects, could be present in anything labeled “garlic extract” on the market, unless specified by laboratory credential.