Natural DHT blockers: what does the evidence actually say?

Pattern hair loss is driven by DHT, produced from testosterone: in genetically sensitive follicles it shortens the hair's growth phase, so strands get thinner with each cycle. I wrote about this separately, together with the mechanism: what DHT is, and what it does to the follicle.

The label "DHT blocker" gets slapped on a lot of things today. It's worth separating what actually blocks DHT production via the 5-alpha-reductase enzyme from what does something else on the scalp: reduces inflammation, improves circulation, or extends the growth phase. Both can be worth something, but they're not the same thing, and they don't have the same amount of data behind them.

For each one below, I look at three things: what was measured, whether there was a placebo group, and how large the trial was. Those three decide how much a number is worth.

Saw palmetto extract is the longest-sold natural 5-alpha-reductase inhibitor. The most commonly cited trial for hair loss involved 100 people and pitted saw palmetto against finasteride: hair grew in 38 percent of the saw palmetto group, versus 68 percent of the finasteride group. Rossi 2012

This number says two things at once. Something did happen in the saw palmetto arm, but the prescription drug produced improvement in nearly twice as many people. The two agents were compared against each other, so we don't know from this how much of that 38 percent would have happened on its own, without any treatment.

Rosemary oil is covered by a 100-person, six-month trial that compared it with 2 percent minoxidil solution in androgenetic hair loss. There was no significant difference in hair count between the two groups at either the third or sixth month. Panahi 2015 Scalp itching, however, was more common in the minoxidil group. Panahi 2015

It matters what this does and doesn't mean. It means the two agents performed similarly by the end of the trial. It doesn't mean rosemary oil is proven to grow hair: that would need a placebo arm, otherwise the similarity could just as easily come from neither agent doing much. On top of that, the comparison was against 2 percent minoxidil, the weaker concentration; 5 percent is the usual strength for men.

Pumpkin seed oil is the only one on this list for which I found a placebo-controlled trial: 76 men, 24 weeks, 400 mg orally per day. Hair count rose by an average of 40 percent in the treated group, versus 10 percent in the placebo group. Cho 2014

This is the strongest data on the list, and it still needs to be read carefully. One trial, 76 people, and a percentage increase in hair count can look large when the starting value is small. There's no larger, repeated trial behind it.

For caffeine, the evidence has two layers. In the lab, on cultured human hair follicles, testosterone suppressed growth, and caffeine counteracted this; on its own, it also stimulated follicle growth. Fischer 2007

In humans, a 210-person open-label trial compared 0.2 percent caffeine solution with 5 percent minoxidil over six months. The proportion of growth-phase (anagen) hairs improved by 11.68 percent with minoxidil and 10.59 percent with caffeine, and the authors concluded caffeine was no worse than minoxidil. Dhurat 2017

The caveat matters here too: the trial was open-label, not blinded, and had no placebo arm. A 2025 review looked at nine caffeine trials, 684 people in total, and paints the same picture: the effect is comparable to minoxidil, but the quality of evidence was low or very low in most of the trials. 2025 review

Ketoconazole is an antifungal active ingredient, used for dandruff and seborrheic dermatitis. Its relevance to hair loss comes from the fact that it reduces scalp inflammation, and the literature suggests it also affects local androgen production.

The most commonly cited trial compared 2 percent ketoconazole shampoo with minoxidil in men. According to the authors, both treatments improved hair density, shaft thickness, and the proportion of anagen follicles to a similar degree. Piérard 1998 The trial was small, and the detailed figures aren't freely available, so I don't quote them. A 2020 review calls ketoconazole a promising adjunct or alternative treatment in androgenetic hair loss. Fields 2020

I use this myself, it's part of my own hair-washing routine.

Green tea extract (EGCG), nettle root, and lists of "DHT-blocking foods" come up constantly. I didn't find a human trial for any of these that used hair as an endpoint; what exists is lab work or animal models. That doesn't mean they don't work, it means we don't know.

"DHT-blocking shampoo" is a separate case. DHT is produced inside the body and acts inside the follicle, while a shampoo sits on your scalp for a few minutes and then gets rinsed out. It doesn't lower your body's DHT level. If a shampoo helps, it does so locally: by calming inflammation or improving the condition of the scalp. On that front, ketoconazole shampoo has the most data behind it.

Microneedling doesn't work on the hormone: it opens temporary microchannels in the upper layer of the scalp and triggers a local regenerative response around the follicle. Its role is therefore quite different from a 5-alpha-reductase inhibitor, and it doesn't replace one either.

If you're curious about your own pattern, I wrote separate pages on that: male pattern hair loss, female hair loss, or the pattern picker if you're not sure yet which is yours. And on how to use it: the 1 mm stamp at home.