January 3, 2023

Does Saw Palmetto Actually Increase Testosterone? | Scientific Studies and Evidence

by Bryan Wellington

I recently ran across an interesting article in my research for Muira Puama, and whether it can boost testosterone. The article mentioned that Saw Palmetto may have some testosterone benefits, and I’d even seen that on some respected hospital sites.

My curiosity piqued, I decided to do as deep a dive as I could on whether there was any actual evidence to backup the claim of Saw Palmetto boosting testosterone. It turned out to be a pretty deep dive, and there was a lot of research on prostate health that I uncovered. Unfortunately, there wasn’t as much data to support the testosterone hype.

Key Findings

Only two studies not related to prostate health showed a testosterone increase with Saw Palmetto–but both were studies of a proprietary supplement.

Prostate studies have shown increases in testosterone in prostate tissue–but not free testosterone or serum testosterone.

✲ Meanwhile, studies of Saw Palmetto on just serum testosterone did not show any increase.

A final report (and one of the most recent on the subject) warned that Saw Palmetto can reduce testosterone–and even lead to adverse effects.

The Positive Studies

I won’t mention brand names, because I don’t want to give the appearance of any kind of bias, but there are two studies of a particular “testosterone booster” whose research authors claim showed a testosterone increase–but one of the studies didn’t use any placebo control, and had no blinds, while the other study did not show a significant increase in testosterone. (For more on why those details matter, read here.)

The first study, which I should note is almost fifteen years old, is riddled with red flags. Any one of them on their own wouldn’t be enough to distrust the article, but taken altogether, they give me pause. For starters, the authors make a conflation of correlations with an enzyme called 5α-reductase, where they state that drugs which inhibit this enzyme increase blood testosterone.

We’ll come to more discussions of 5α-reductase later, but for now, you should know that it’s a complicated enzyme whose role changes as we age. When males are young a deficiency in 5α-reductase does not raise testosterone, as these authors claim–it in fact can make young boys look and sound like young girls.

From there the study hardly gets more reliable. They then move on to some other dubious statements, finally resulting in a claim that a proprietary blend of Saw Palmetto increases testosterone. The second study is more recent, only went for two weeks, and used the same proprietary supplement. They were careful to point out that results were not significant.

More Rigorous Data

There was a very well-run study (double-blinded and randomized) that saw a significant increase in serum testosterone following Saw Palmetto treatment. The one caveat to this study is that the Saw Palmetto used for those specific results was doctored to have higher than normal levels of a plant membrane compound called β-sitosterol (beta-sitosterol).

This compound has been seen in other studies to increase gonadal activity in animals, and it is already present in Saw Palmetto; but only the Saw Palmetto with artificially higher levels of beta-sitosterol.

Next we have three studies that serve as good foundations of the field when it comes to enlarged prostate conditions (called BPH, or benign prostate hyperplasia). BPH studies often deal with testosterone levels, specifically of the prostate tissue, because there is some data indicating that the relationship between DHT (dihydrotestosterone) and testosterone in the prostate may affect its size and tendency to become cancerous.

A foundational study (often erroneously quoted to say that Saw Palmetto increases all testosterone) found that the herb did increase testosterone in the prostate, and lower DHT. These data have been replicated in animal studies and later human studies. What’s important here is that there is not strong evidence that Saw Palmetto can increase overall testosterone levels–only that it can increase testosterone levels in the prostate.

It’s fair to ask why that one body part is so distinct. To answer that, we come back to the enzyme 5-alpha reductase. This enzyme is responsible for the body converting testosterone into DHT. 

A lot of “man boosting” websites will decry the presence of DHT, saying that it’s eating up all of a man’s free testosterone. There is some case to be made for that, but DHT’s role changes throughout our life. In pre-puberty and adolescence, DHT is responsible for growing facial hair and a deepening voice. In later years it’s responsible (it seems) for enlarged prostates and losing hair (alopecia).

Saw Palmetto has been shown to decrease DHT, by inhibiting the 5-alpha reductase process. This has resulted in more testosterone present in certain tissues where testosterone converting to DHT causes problems–like the prostate. But all Saw Palmetto has been (tentatively) proven to do is prevent testosterone in the prostate from converting to DHT.

No study has definitively shown that this means more free or serum testosterone in the rest of the body–certainly not enough to show up in stronger muscles, sperm morphology, or any other health indicator.

A Final Roll Call

Lastly, I’ll point to two studies that should serve as a warning. The first is a study that, many years ago, looked at all the BPH data and set about to determine if there was any overall serum testosterone increase from the use of Saw Palmetto (referred to in this report by its scientific name, Serenoa repens). They found no change in testosterone, and concluded that there were no body-wide indications that Saw Palmetto effected testosterone.

Perhaps the final nail in the coffin comes from a clinical study of a patient who was taking Saw Palmetto for BPH, long term, and then started suffering from adverse effects (AE). These included loss of libido and ED. After blood samples were taken, his doctors confirmed that he had hypogadism–clinical, medically low testosterone.After further study, they concluded that in his case, Saw Palmetto had caused low testosterone. They then performed more research, and found that after a systematic review of their available research (to which the public is not privy), they concluded that long-term Saw Palmetto use was associated with: lower testosterone; ejaculation disorder; impotence; and gynecomastia (“man breasts”).


I’m always happy to report when an herbal remedy is backed by good science, as with Ashwagandha root boosting testosterone. But sometimes the data just isn’t there–or worse, some of the data shows that the herbal remedy may actually be bad for the thing people are taking it for.

It seems that Saw Palmetto may fall into that latter category. While it appears to be a viable option for men with enlarged prostates, even the best the data say Saw Palmetto won’t have any effect on total testosterone in the short term. Not to mention that it also seems that there are long-term testosterone-decreasing AE associated with it.


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