There has been some research on spearmint suggesting anti-androgen effects in PCOS, which is a bit unexpected to me as I wouldn't expect mint-family herbs to have much hormone modulating effect at all. I would imagine there to be similarities in profile between spearmint and peppermint so perhaps a related mechanism is involved, although I would probably expect the opposite outcome as a naive layperson. But I haven't closely evaluated the paper nor do I know whether there's been much else suggesting this

It is important to remember that herbs are difficult to study in this setting compared with isolated compounds -- likely because their pharmacological and chemical compositions are sensitive to many factors: hour and season of harvest, form consumed (raw powder, alcohol extract, cold water infusion, fat emulsion, hot water infusion, combustion, pyrolysis, essential oil), part consumed (leaf, root, flower, seed), among staggeringly many others. Anyone with experience consuming cannabis or coffee can probably testify to the above

Not to mention that the pharmacologically active compounds in many plants are far from being comprehensively understood, let alone their interactions and dynamics

This isn't to say that every claim about herbs is to be taken seriously. My point here is more that there is no good reason to dismiss the herb itself as a cause yet simply because it's an herb and a fairly mundane one at that. There are easy examples of herbs which have pronounced physiological effects, used for recreation, performance enhancement, as literal poison, to induce labor, to thin the blood -- among others.

https://pubmed.ncbi.nlm.nih.gov/19585478/

Peppermint is now familiar to most people as the ubiquitous taste of toothpaste, even moreso than candy, food, or drink.

If we cue university student volunteers on Toothpaste -> Selfcare -> Weightloss I wonder what happens.

I also wonder what placebo was used, and to what effect. The typical flavoring agent to make something peppermint-flavored is peppermint essential oil (or cornmint, spearmint, etc), and I don't know how you'd make it convincing without also including a bunch of hypothetically active compounds. The paper lists Schweppes Peppermint Cordial, without mint on the ingredients label. "Peppermint cordial" used as flavoring was historically 10% peppermint oil, and today the Schweppes product they cite just lists "flavourings" as ingredient.

But weight/mass didn't change one bit (okay exaggeration, but not by much), so maybe peppermint helps relieve gas. Who knows? There's a lot that this data could mean, and no simple way to figure it out.

Peppermint oil is a known laxative, so I wonder if that made a difference

Peppermint oil has traditionally been used in India for digestion, so you may be on to something. I remember this particular brand growing up: https://www.amazon.com/clp/B001NQ7S9G (no relation).

Nothing but blood pressure and heart rate was significant, and heart rate only barely so. I wouldn't read anything into the other numbers. It was a 20 day study, you aren't going to get long term outcomes from that.

It is a 0.7% drop, so very likely to not be significant unfortunately.

I'm wondering if caffeine was accounted for in this. One thing I seem to recall is peppermint tea has some inhibition of CYP1A2. I notice it's missing from the wikipedia page now, so maybe this was a flawed study or something... figured I'd mention in case anyone else knows.

At least this study says the activity was reduced, not significantly though: https://www.sciencedirect.com/science/article/abs/pii/S02786...

I'd think weight could be causal for hypertension result or sentiment over health measurement could have been causal for weight or the study could just be too small.

I think its reducing bloating.

Maybe it helps with weight loss (I wish)

Yes, and looking at dietary data, the study says that there is no difference in their diets, but carbohydrate intake drop from 217g to 171g. I don’t see how that’s insignificant.

Wild-ass guess: maybe the aftertaste of peppermint oil twice daily leaves people who are already unhealthy wanting to snack less, leading to minor weight loss.

I think that's more than likely here as "placebo" was literally this peppermint cordial [1].

They say it doesn't have peppermint oil in it... but it does list "flavorings" and I don't know how you make something taste like peppermint without using peppermint (or why you wouldn't).

The other possible explanation is 1 group is basically drinking an extra 200ml of water with a microscopic amount of peppermint oil, and the other group is drinking an extra 200ml of sugar water. The researchers may have literally just stumbled on the fact that more water and less soda has positive health impacts.

[1] https://www.tesco.com/shop/en-GB/products/254854798

Very likely. If they really wanted to make the results a bit stronger, they could at least have switched the two groups after 20 days.

If you've tried 20 things, you've probably won that lottery. It's an easy lottery to win.

Classic xkcd on this topic https://xkcd.com/882/

Based on your new information, I think it would be good to test the effect of supplemenths vs supplemints.

im bored and want to buy some peppermint sups. someone drop a brand and sell me on it in the marketplace of ideas

it's 2026, better sources than webmd exist: https://www.supplementdex.com/ or examine.com

Even worse, the placebo group drank peppermint cordial. The researchers are arguing there is no peppermint oil in it because it's not a listed ingredient, but the listed ingredients have "flavorings". Which, I'd be shocked if it weren't peppermint oil.

This is the "placebo" they used [1]

[1] https://www.tesco.com/shop/en-GB/products/254854798

Publish or perish mentality + difficulty funding a larger study is why this gets published. There's nothing particularly wrong with it as an exploratory study, the big problem is the lack of incentive to try to reproduce the results and publish the inevitable null result.

Maybe because it suppresses/modulates certain hormones? I'd be careful ...

https://www.sciencedirect.com/science/article/pii/S009042950...

> We performed this study because of major complaints in our area from men about the adverse effects of these herbs on male reproductive function.

I'm guessing that this number is the result of the average of "x" people in the study, and not an individual measurement. But, yeah, I see what that looks like.

I grew up sailing on the Chesapeake, and we used it for seasickness.

This study compared a group that drank peppermint oil against a group that drank peppermint oil.

These researchers picked a placebo that was the thing they were trying to test. The dingdongs didn't think that "flavorings" could include peppermint.

So I'd hold off on singing the praises of peppermint as this is a pretty obvious flaw to the study.

This is the "placebo": https://www.tesco.com/shop/en-GB/products/254854798

This is my favorite soap, by far, for what it’s worth. The peppermint one, in fact. ALL ONE!

But do you spit or swallow?

Those old York's Peppermint Patty ads were on to something.

> The result might be real

How could they be? The peppermint cordial almost certainly contains peppermint oil!

The authors chose it because it wasn't explicitly listed on the ingredients list, but what was listed was "flavorings". I highly doubt coca cola used anything other than peppermint oil to flavor a peppermint drink. That would be bizarre to say the least.

>50 µL of supplement diluted into 100 mL of water

pretty tiny amount of peppermint was consumed

I've got an n=65 about hibiscus and blood pressure, which has been better well known for awhile. https://www.ars.usda.gov/news-events/news/research-news/2008...

Silence, we have disruptive direct to consumer peptide startups that need to pump.

From PLOS One as well! I remember in college, I was taking a bio class that taught how to read journal articles...and a psych class that was assigning them. Psych class assigned almost solely PLOS One articles...which didn't survive the criticism I was being taught in the bio class lmao

If there's anything consistent about HN as long as I've been on it, it's that HN is orthorexic.

Doesn't it make sense to run a small trial before running a big trial?

Also, peppermint oil is unpatentable. Neither Merck nor Novo Nordisk can hope to make billions from it, and without the profit motive, the list of institutions with both the budget and the will to fund a 500+ participant study is pretty short. This might be the best we can get.

And yes, I get that a small trial has less of a value...

This study did not involve tea. Do you have links to studies showing herbal tea has similar effect? (Sincere question, I drink a lot of peppermint tea for its mild decongestant effects.)