Rosemary oil for hair growth? How to spot bad science
Summary
TLDRThis video script delves into the efficacy of rosemary oil for hair growth, scrutinizing a study that claims its effectiveness rivals minoxidil. The host expresses skepticism, highlighting methodological flaws, data inconsistencies, and the unreliability of relying solely on mechanistic reasoning. The script underscores the importance of critical assessment of scientific studies, the limitations of peer review, and the necessity of clinical trials. It concludes by advising viewers to approach rosemary oil with caution and consider more established treatments for hair loss.
Takeaways
- 🌿 Rosemary oil is often cited as a natural treatment for hair growth, with some claiming it's as effective as minoxidil, a common hair loss treatment.
- 🔬 A 2015 study frequently referenced for supporting rosemary oil's efficacy has been criticized for methodological issues, casting doubt on its reliability.
- ⚖️ The study compared rosemary oil to a 2% minoxidil solution, which is weaker than the 5% solution typically recommended by dermatologists.
- ⏱️ The study's duration of 6 months is considered too short to accurately assess the efficacy of hair growth treatments.
- 📊 The study's data, including identical baseline and 3-month hair count numbers, contained errors that raise questions about the validity of the results.
- 📝 Peer review, while intended to ensure scientific quality, is not foolproof and can sometimes allow flawed studies to be published.
- 🌐 The study has been cited numerous times, indicating that even peer-reviewed articles may not critically assess the sources they reference.
- 🍃 Rosemary oil's potential mechanisms for hair growth, such as increased blood flow and antioxidant properties, are theoretical and not conclusively proven.
- ⚠️ The variability in rosemary oil's composition due to factors like growing conditions and extraction methods can affect its potential efficacy.
- 💧 The study suggests a dilution ratio of 1:161 for rosemary oil, highlighting the need for caution to avoid irritation, especially given reports of increased scalp itching and dandruff among users.
Q & A
Is rosemary oil considered a scientifically backed treatment for hair growth?
-While some studies suggest rosemary oil could be as effective as minoxidil for hair growth, the evidence is not conclusive due to methodological issues and inconsistencies in the research.
What are the potential mechanisms by which rosemary oil might promote hair growth?
-Rosemary oil is thought to potentially increase blood flow to hair follicles and act as an antioxidant, neutralizing free radicals that could contribute to hair loss.
What are the common issues with the study that compared rosemary oil to minoxidil for hair loss treatment?
-The study has been criticized for using a low concentration of minoxidil, having a short duration of treatment, and presenting suspiciously identical data points that raise questions about the accuracy of the results.
How does the peer-review process in scientific journals work, and what are its limitations?
-Peer review involves other scientists evaluating an article's quality before publication. Limitations include variable quality, potential bias, and the fact that less popular topics may not receive as much scrutiny.
Why is it important not to rely solely on the abstract of a scientific paper for understanding its findings?
-Abstracts are summaries that may not include critical limitations or may overstate results. They should be used to determine if the full paper is relevant, not as a substitute for reading the entire study.
What are some red flags in the rosemary oil study that question its reliability?
-Red flags include identical data points that should logically differ, discrepancies in figures, and missing methodology for collecting certain data, suggesting potential flaws in the study's execution and reporting.
How do seasonal variations and other factors impact hair growth, and how might they affect the results of hair loss studies?
-Seasonal changes, stress, and other factors can cause natural fluctuations in hair growth and shedding, potentially leading to misinterpretations of treatment effects in studies.
What is the role of mechanistic reasoning in evaluating the potential efficacy of treatments like rosemary oil for hair loss?
-Mechanistic reasoning can suggest how a treatment might work but is not definitive evidence of efficacy. It's important to consider clinical trial results, which account for the complex interplay of mechanisms in the body.
Why might some people experience increased hair loss or scalp irritation after using rosemary oil?
-Rosemary oil contains allergens and irritants like camphor, carnosol, and cineole, which could potentially exacerbate hair loss or cause scalp irritation for some individuals.
What are some alternative treatments for hair loss that are recommended over rosemary oil based on the evidence presented?
-Proven treatments like minoxidil are recommended over rosemary oil due to stronger clinical evidence supporting their efficacy. It's also advised to consult a healthcare professional to address potential underlying causes of hair loss.
Outlines
🌿 Rosemary Oil's Effectiveness on Hair Growth
The paragraph introduces the topic of whether rosemary oil is scientifically proven to aid hair growth. It mentions that many doctors and scientists support the claim, with studies suggesting rosemary oil can be as effective as minoxidil. The paragraph also discusses the science behind rosemary oil's potential benefits for hair growth, particularly in treating androgenetic alopecia. It highlights the importance of consistency in applying rosemary oil and the need for at least six months of use to gauge its effectiveness. The speaker also expresses skepticism about a frequently cited study, hinting at flaws in the research that others have overlooked.
🔍 Critical Analysis of Rosemary Oil Study
This section delves into the critical analysis of a study that compares rosemary oil to minoxidil for treating androgenetic alopecia. The study, published in a peer-reviewed journal, has been widely cited despite its questionable quality. The paragraph discusses the process of peer review in scientific publishing, explaining how it is intended to ensure research quality but is not foolproof. It points out issues such as less scrutiny for less popular topics, potential biases, and the variable quality of peer review. The speaker emphasizes the importance of reading scientific papers carefully, especially the methods and results sections, to assess their reliability.
🕵️♀️ Identifying Flaws in Scientific Research
The speaker identifies specific issues with the rosemary oil study, including the use of a low concentration of minoxidil, which is a known treatment for hair loss. They also question the study's short duration, as hair growth cycles can span years, making a six-month study insufficient for a reliable assessment. The paragraph discusses the unreliability of before-and-after photos and the implausibility of the hair count numbers reported in the study. The speaker suggests that the study's methodological issues extend to other aspects of the research, casting doubt on its overall validity.
📊 Understanding Hair Growth Data and Its Limitations
This paragraph further scrutinizes the data presented in the rosemary oil study, pointing out inconsistencies and errors in the reported hair count numbers. It discusses the small differences in hair count between the treatment groups and how these differences are not statistically significant. The speaker also considers seasonal variations in hair growth and how they might affect study outcomes. The paragraph highlights the potential for perception bias in self-assessments of hair loss and the unreliability of anecdotal evidence in evaluating treatment efficacy.
📚 The Role of Mechanistic Evidence in Hair Loss Treatments
The paragraph discusses the limitations of relying on mechanistic evidence alone to support the use of rosemary oil for hair loss. It contrasts this with clinical trials, which provide more concrete evidence of a treatment's effectiveness. The speaker explains that even promising lead compounds with strong mechanistic evidence often fail in clinical trials, emphasizing the importance of actual clinical data over theoretical benefits. They also address the variability in rosemary oil composition and the potential for allergens and irritants to counteract any benefits, concluding that rosemary oil is not a reliable treatment for hair loss.
💡 Alternative Hair Loss Treatments and Recommendations
In the final paragraph, the speaker advises against using rosemary oil for hair loss due to the lack of compelling evidence and recommends consulting a healthcare professional for proven treatments. They suggest that hair loss may be symptomatic of an underlying condition that requires medical attention. The paragraph also touches on the importance of using proven treatments like minoxidil and being cautious of remedies that delay the use of more effective interventions. The speaker concludes by directing viewers to additional resources for understanding hair care science and the evaluation of ingredient efficacy.
Mindmap
Keywords
💡Rosemary oil
💡Minoxidil
💡Androgenetic alopecia
💡Scientific proof
💡Dermatologists
💡Peer-reviewed
💡Abstract
💡Clinical trials
💡Mechanistic logic
💡Dilution
Highlights
Rosemary oil is suggested by some doctors and scientists to be as effective for hair growth as minoxidil.
A 2015 study indicated that rosemary oil could be beneficial for patients with androgenetic alopecia.
Topical application of diluted rosemary oil on the scalp may be as effective as minoxidil, according to some studies.
For rosemary oil to potentially regrow hair, consistent use for at least six months is recommended.
The study often cited for rosemary oil's efficacy has been criticized for its methodology and data integrity.
The peer-review process is explained, highlighting its importance and limitations in scientific research.
The study comparing rosemary oil to 2% minoxidil has been widely cited but contains significant flaws.
The use of 2% minoxidil in the study is questioned, as 5% is more commonly recommended for hair growth.
The study's six-month duration may be too short to accurately assess hair growth treatments.
Discrepancies in the study's data, such as unchanged hair count numbers, raise doubts about its reliability.
The study's abstract may be misleading, suggesting better results than the full paper supports.
The potential for seasonal variation and other factors to affect hair growth is discussed, impacting study results.
The study's self-assessment results are questionable, with all participants reporting improved hair loss.
Mechanistic reasoning is discussed as an insufficient basis for the efficacy of rosemary oil without clinical support.
The potential for rosemary oil to block 5-alpha reductase is mentioned, but the study has limitations.
The importance of consulting with healthcare professionals for hair loss treatment is emphasized.
Dilution of rosemary oil is advised to minimize potential irritation and allergic reactions.
The video concludes that rosemary oil is not recommended for hair loss treatment based on the available evidence.
Transcripts
hey chicken sauce Michelle here
is rosemary oil a natural science backed treatment for hair growth?
according to a lot of doctors and scientists and trichologists across the internet yes
there is scientific proof rosemary oil works as well as minoxidil
here's the science behind why rosemary oil and rosemary water work to grow your hair
2015 studies showed rosemary oil to be just as effective as minoxidil
best and worst hair loss treatments according to dermatologists
my take away from this is that rosemary oil can be beneficial for patients suffering from
androgenetic alopecia
use topical rosemary oil diluted onto your scalp studies show it's as effective as minoxidil
here are three derm approved hacks for using rosemary oil to help regrow your hair
yes it can help but you have to be consistent with use for at least 6 months to determine
whether it works for you or not
and it all seems to come down to this one study
for a long time I didn't look into it I just kind of assumed it was legit because everyone
cited it
anyway it turns out I shouldn't have assumed that because when I finally looked at the
study
[exhale] I really wasn't prepared for how bad the study
was
so today I'm going to explain why
I'm going to talk about what the science actually tells us about rosemary oil and hair loss
whether it's safe to try
and give you some tips for critically assessing studies so you don't fall for bad science
and as a bonus you'll also understand how a peer reviewed journal published this AI
generated rat… thing
so this is the study that everyone is citing
rosemary oil versus minoxidil 2% for the treatment of androgenetic alopecia a randomized comparative
trial
it was published in skinmed which is a peer-reviewed journal and peer reviewed is generally considered
higher quality when it comes to scientific sources and it kind of is but it also really
isn't
to understand peer review we need to talk about how science works
back in the day when scientists looked like this to do science you would just
poke around some random stuff
find something interesting
science was pretty new back then so everyone was just discovering stuff everywhere
you would go tell your scientist pals about it at your science club meetings
they'd clap or argue with you
some of them would build on your discoveries in their research
you might write a book about it or get an article published in a magazine which in science
is called a journal
scientists would clap or argue with you
if they really didn't like it they might burn down your house
what are you doing
why is the door locked
but after a few hundred years people had discovered a lot of stuff so science had gotten a lot
more complex
a single journal editor didn't know everything about the subject anymore
so to work out which articles were good enough to publish they would ask other scientists
who knew more about that topic to weigh in
by the 1960s with super advanced things like photocopiers this process of peer review which
is just getting other scientists to decide if your articles were good or not this became
way more structured
these days the general process is
you do some research
you write an article and you send it to a journal
the editor checks that it mostly looks okay
if the research is important enough (that is going to come up again later) and if it
matches the journal topic
if yes they send it to usually two or three scientists who specialize in your area
these reviewers will check things like whether the equipment you're using will actually work
for what you're doing
whether your conclusions make scientific sense with what we already know from all of the
other studies out there
the reviewers send feedback to the editor and your article will be accepted or rejected
usually if it's accepted you'll still have to make a few changes
then your paper gets published
yay
after the paper gets published then there's post publication review which is where other
scientists will comment on your work or try to repeat your experiments
papers might end up corrected or retracted
it might end up compared to to other studies in reviews and textbooks and add to our general
body of scientific evidence
that is the less complicated established science that you might get taught at school and university
now this system is generally pretty good or at least it's probably one of the better systems
for building scientific knowledge what we know about how the world works
but it is really far from perfect
here are some of the big issues with peer review and this is a very incomplete list
less popular topics aren't scrutinized as much
plenty of dodgy papers get through and it is especially the case with an area like beauty
where a lot of the most rigorous research never gets published
I talked about this on my video on whether retinol is a scam
so there is not a lot of replication and not a lot of scientists are discussing and critiquing
the studies that do come out
plus peer review isn't really rewarded much peer reviewers aren't paid or recognized when
they do good peer review
peer review is anonymous and voluntary so the quality is pretty variable and it tends
to take a really long time
if a reviewer is checking a paper that they know probably isn't going to have a lot of
people reading it they might not take it as seriously maybe they won't read it super closely
peer reviewers can also be biased they might not read it as critically if one of the researchers
is really well known in the field or if they come from a prestigious institution just because
you would expect them to do good research
it's actually a really well-known hack for getting papers published quickly with minimal
revisions just stick a well-known author on there
it's one reason why there's so many examples of papers now from high-profile authors being
retracted for blatant issues like bad Photoshop
there are also dodgy journals that might not actually do peer review they just don't bother
sending the papers out for peer review they just put it through a process and tick it
off
now a dodgy journal doesn't mean that the study is automatically bad
it just means that you don't know if it's actually being peer-reviewed properly
at the same time a good journal doesn't mean that the study is automatically reliable
it's just that hopefully the obviously dodgy stuff is more likely to have been weeded out
so all of this just means that you have to be really careful when you're looking at a
scientific paper you can't just take what it says at face value you need to read the
whole thing slowly and carefully to work out if you should actually trust what it says
and this brings us to the next problem with papers - a lot of the time you might not actually
be able to read the full thing
lots of papers are behind paywalls and it is a pretty crappy system because the journals
don't pay for the research it's taxpayers or industry the peer reviewers review for
free and the authors usually have to pay for the journal to publish the paper
but then the journal or the publisher gets to charge people to read it and no the authors
do not get royalties
there are regulations coming in to make government funded research publicly available but it
is an ongoing process
but the part that is always free to read is this which is called the abstract
it's meant to be a summary of the paper and I think it's what a lot of people were basing
their rosemary oil opinions on without reading the full actual paper
but this is a trap
it is the most common trap with reading studies
never trust the abstract
this article I cowrote lists a whole bunch of traps but this one is the biggest
you're really just meant to use the abstract to work out if you should read the rest of
the paper if it's relevant to what you're researching
the abstract is really short they can't include a lot in there and you won't be able to critically
assess if what they're doing is actually making sense
it'll be missing a lot of the limitations of the study and the authors probably only
included the results that they wanted to highlight
and abstracts are usually not an accurate summary a lot of the time it's treated like
it's advertising for the rest of the paper to make you want to read the full study
the abstract is the first thing that journal editors and reviewers will see
well after the title and the authors
there are more papers being submitted than can actually be published so research that
comes across as more important is going to be more likely to be published so if you read
a lot of papers you will notice this pattern which is the abstracts usually hype up the
paper a bit too much
so think of the abstract as like the two sentence synopsis of a movie
like this sounds quite promising
this sounds reasonably straightforward to understand
this doesn't sound like an incredible work of genius
and this paper's abstract actually sounds pretty good
there's a total of 100 people which is a lot for a cosmetic study
more subjects means more repetition so the results are less likely to be a fluke
the treatments were used for 6 months which seems like a reasonably long time
rosemary oil also isn't being tested on its own it's being compared with minoxidil which
is one of the most popular hair loss treatments
this isn't quite as good as comparing it against a placebo treatment which has no active ingredients
but a lot of cosmetic studies just use the treatment on its own so again this is a promising
sign
now the results part of the abstract also sounds really impressive
"both groups experienced a significant increase in hair count at the six-month end point"
"no significant difference was found between the study groups regarding hair count either
at month 3 or month 6"
a word of warning here in science significant doesn't mean significant like there was a
lot more hair it basically means that statistically the the increase is pretty likely to be because
of something actually happening here rather than because of random variation
significant doesn't tell you about the size of the increase it could still be really small
like just one extra hair
scientists sometimes use words a bit weirdly it is another of the many traps that you can
fall into when reading papers
so if this abstract was all that you read and you assumed that it was accurate then
rosemary oil does sound really promising
so let's ruin it all by
reading the actual paper
here are the standard parts of a scientific paper
the most important parts to read are the methods and the results because those tell you what
the paper is actually about what original research the authors did
it is the whole point of the paper
the problem is that these are usually the hardest parts of the paper to read and evaluate
they're more technical it's where you get complicated words and numbers and symbols
and you do need to know a bit about the topic already to be able to assess these to any
proper level
the abstract introduction discussion and conclusion are much more friendlier to read they mostly
have normal words and they tell a nicer story
but they are the author's interpretations of what they found so those are going to be
a bit more subjective and more liable to spin
and if the interpretation here is sus that is a huge red flag but before we can judge
whether or not it is sus we need to look at what it is we're interpreting
now all of this sounds really intimidating like you have to be an active researcher to
spot bad science but I don't think that's actually the case
one thing I've noticed in my 12 years of interpreting and talking about beauty science is that a
paper that has really big problems with the methodology usually will mess up in other
places too
so you don't really need to be that familiar with experimental methods to be able to flag
a paper as sus
as a paper that you probably don't want to take too seriously
and this paper is a really good example
what made me go and read this paper in more detail is coming across a reel on Instagram
from Dr Leona Yip who is an Australian dermatologist
she pointed out some of the problems with this paper and some other dermatologists have
pointed them out too
a lot of people don't realize that dermatologists they don't just look at skin conditions they
also look at hair and nail conditions or at least they look at the bit that is living
which is very much the bit that's involved in hair loss
problem one 2% minoxidil
minoxidil is one of the best studied treatments for hair loss and that's why this paper sounds
so impressive
but the detail here is 2%
the vast majority of dermatologists would recommend at least minoxidil 5% to grow hairs
because 2% is just too weak
I honestly don't even remember myself when I had asked a patient to use minoxidil 2%
in the last 10 years cos I think they'll be quite disappointed
we know that 5% minoxidil has much better efficacy when compared to 2% minoxidil so
rosemary oil is really compared against the weaker treatment
problem two is the duration
6 months does sound like a long time but it's actually not a long time for hair growth
hair grows in a cycle and the average length is years
so 6 months is actually considered really early
it's unreliable to assess any treatment efficacy as early as 6 months so I suspect if we looked
at the 2-year mark minoxidil 2% will likely be more effective than rosemary oil
but like I said there are more general red flags in the study as well
here's one that I think anyone can spot
look at the sample before and after photos they're not exactly impressive
I think this really reinforces what the dermatologists were saying you just don't really expect that
much of a result after 6 months with 2% minoxidil
the different angle and lighting for minoxidil is pretty weird and it's kind of hard to work
out what you're looking at it looks like it might be a bit closer up
but the thing that really blew my mind and stopped me from taking this study as evidence
of anything was when I saw the actual hair count numbers
here's the baseline hair count numbers at the start of the trial and here is what they
are at 3 months
they are exactly the same numbers
this has to be a typo it is basically impossible to get the exact same mean and standard deviation
for two groups of 50 people 3 months apart
you probably couldn't even get that an hour apart
and whoever made the graph from the data didn't see an issue with these numbers
they used them in the graph as well
the baseline and month three numbers are exactly the same
and obviously you are allowed to have typos it doesn't mean that the study is automatically
bad I mean I have typos all the time in my posts I can't really judge
but these are two of their key data points there are only six numbers that really matter
in this whole study they are the whole point of the study and two of them are wrong
can we actually trust the other four numbers?
this is the sort of thing that should be picked up immediately in peer review but this is
a paper that has four authors who all supposedly looked over it and OK'ed it both in the results
part and in the graph
it also supposedly has peer reviewers who looked at it and none of these people corrected
it
if I was a peer reviewer for this article I would be asking to see the raw data and
checking all their calculations
and right now I've been assuming that the month three numbers are the ones that are
wrong but it could actually be the baseline numbers that are wrong
if it's the baseline numbers those are the ones that the whole "experienced a significant
increase in hair count at the 6 month endpoint" result is based on
I haven't found any corrections of this or any indications that anyone has reached out
to the researchers and clarified what is going on even though this has been cited 93 times
as of February 2024
we will come back to this later
okay so every time I look at this paper I just see more issues and and I'm not that
great at stats and I haven't gone through every single word really carefully so I'm
sure there's still tons of stuff I've missed
if you take the means of these two you get 24.08 not .03
16 plus 13 out of 100 is 29% not 21%
figures 5 and 6 are for greasy hair and dandruff but they are exactly the same
well the formatting is like a few pixels off
but if you look at the text dandruff should have way lower numbers they should be close
to 16% so they've just messed up the figure
these figure references are just wrong figures five and six aren't about scalp itching that
is actually meant to be figure seven
and you don't use a rating scale for depression to measure hair loss you just don't
depression and hair loss are completely different medical conditions
and this all just really highlights what I was saying before a paper with serious methodological
issues tends to have a lot of other issues and you don't need to be able to spot all
of these to know that this paper isn't reliable
and again it's not like having some typos completely invalidates the paper there are
lots of good papers out there that might have mixups with figures that might happen during
the final formatting and then the journal will issue a correction and everything is
fine
but if there's just a whole bunch of issues like there are here that is a huge red flag
that something is just not right
and some of these especially the calculation errors
you don't have the full data set available so you just have to kind of trust that they
did the calculations correctly and I mean
now even if we assume that these numbers for baseline and month six are correct it is still
really not that impressive
if we look at the absolute numbers the average difference here is either six or two hairs
this is a group where the standard deviation is about 50 hairs that means if you take the
middle 2/3 of people there is about 100 hairs difference between them six or two hairs is
just so small
and this graph shows how small this difference is if you just had to eyeball this graph and
look at the difference between these columns there just isn't really a big difference at
all
as a percentage the rosemary group increased by 5.5% minoxidil increased by 1.6%
plus here is the thing about hair the amount of hair that we have on our heads will naturally
fluctuate
that's because there are three stages of hair growth which are called anagen catagen and
telogen
the hairs on our heads are distributed into these three stages so we have more or less
consistent shedding but it isn't completely consistent we have a bit more hair in spring
so more hairs are in the anagen stage and we shed a bit more hair in autumn so more
hairs are in the telogen stage which is when they can fall out
it's like a weak version of how animals will shed their winter coats all at once but for
some people this difference can lead to noticeable shedding at different times of the year
this study took place between April 2010 and June 2011 in the northern hemisphere so if
you had a few more people starting their 6 months around June 2010 than over here or
over here then you would see an increase in the average hair count even if the treatment
wasn't having any effect
and if you look at the hair counts in other studies for the placebo treatment which is
where they have no active ingredients you can sometimes see similar or bigger fluctuations
in this study you can see that the placebo group goes from an average of 132 to 191 hairs
which is an increase of 45%
if we look at what happened in this study with minoxidil 2% at 6 months it actually
gave an increase in terminal hair count of 123% which is a lot more impressive than 5%
and as well as seasonal variation there are a whole bunch of other things that could be
impacting hair growth
it could be the fact they're massaging the scalp twice a day it could be something else
in the lotion having an effect
the details of the lotion aren't given in the paper
and these fluctuations could also explain why so many people on social media claim that
rosemary oil worked for them
one thing that we haven't talked about yet is that sudden hair loss often happens because
of a specific stressful event for example if you've been really sick or if you've been
really stressed and honestly that kind of covers all of us over the last few years
this sudden hair loss is called telogen effluvium and it's common with covid as well as things
like sudden weight loss or surgery and after the stressful event stops your hair will gradually
grow back
but usually it's when your hair is at its worst that is when you're going to be looking
at remedies and trying out things that you see promoted on social media like rosemary
oil
and so you'll see your hair grow back right after you've tried them and you'll think it's
the treatment working even if it was going to grow back all along anyway
this effect is called regression to the mean and I talk about this more in my video on
why anecdotal evidence isn't really reliable
there's also the issue of perception a lot of things do impact whether we think something
works and this can actually be seen in some hair loss studies
in some studies as well as looking at hair count they also asked the subjects whether
they felt like their hair loss improved
so for example in this study you can see that a lot of people felt like the hair loss was
worse after 16 weeks of using 5% minoxidil even though according to the photographs none
of them were worse
and in this rosemary oil study the self assessments do seem maybe a bit too good to be true
at 3 and 6 months all of the people using rosemary oil said that the hair loss had decreased
none of them said no change or that it got worse
for 2% minoxidil of the people said that hair loss decreased at 6 months and only seven
people said there was no change or it got worse at 3 months
now if you look at other studies even in studies that use 5% minoxidil you'll see people saying
that there was no change even with much bigger average changes in hair count
so it just seems like there's something very weird going on in this rosemary oil study
and as you'd expect for a treatment that probably doesn't have that much of an effect as well
as people on social media saying rosemary oil worked for them there are also heaps of
people saying rosemary oil actually made their hair loss worse
so what does this study actually tell us I don't think it really tells us much at all
the most generous thing we could say in my opinion is that
in a study that has really sus numbers where a low concentration of minoxidil unsurprisingly
didn't do very much rosemary oil also didn't do much
and this shows us another problem with the scientific literature
peer-reviewed articles cite other peer-reviewed articles and a lot of the time they don't
actually look very closely at them
this rosemary oil paper has been cited 93 times and just to give an indication of the
problem and how so much crap gets through peer review here are just the first eight
articles that cited this paper I got off Google Scholar
only one of them even indicates any sort of skepticism about the study
there are a few other studies with rosemary oil but they mostly use mixtures where rosemary
oil is just one of the components so it doesn't really tell us much about rosemary oil specifically
but even if that wasn't an issue the studies themselves aren't super convincing either
okay so if the only clinical study showing that rosemary oil works for hair loss is pretty
unconvincing what are we left with
well the intro and the discussion do mention why they wanted to look at rosemary oil in
the first place
it could potentially work in ways that are thought to improve hair loss in other words
it has potentially beneficial mechanisms of action
it could potentially increase blood flow to hair follicles and it's also an antioxidant
which could neutralize reactive free radicals which could be theoretically contributing
to hair loss
but the problem with relying on this sort of mechanistic logic is that there are a lot
of mechanisms happening inside your body and they can have completely opposite effects
so you can usually come up with mechanistic reasons why a particular ingredient could
cause both good and bad outcomes
it's a lot like trying to work out whether your friend Brian is going to be early or
late to lunch today
you can come up with lots of reasons why he might be early
he doesn't live very far away
he likes to wake up early
he has a car and he's a good driver
he is usually a pretty hungry dude
you can probably also come up with lots of reasons why he might be late
he has a busy job
it's hard to get parking near the cafe
it's raining there's a bit of traffic
and yeah some of these reasons are more convincing than others sometimes these reasons could
be so convincing that you pretty much know
like if Brian posted an Instagram Story 2 minutes ago of his flat tyre
but most of the time these reasons are nowhere near as useful as looking at past examples
of the same outcome
in other words is Brian usually early or late when you meet up?
and the closer the past examples are to your current situation the better your guess will
be
is he usually early or late when you've met up at this specific cafe for lunch before
when it's raining and there's a bit of traffic?
and that's why clinical trials which is where the treatment gets tested on actual people
and the outcomes get measured
that's why they are so useful they give us a gauge on what happens when all of these
competing mechanistic reasons add up which ones outweigh the other ones
my PhD was in medicinal chemistry which is the start of the drug discovery pipeline
we would usually start with really promising ingredients which are called lead compounds
with good mechanistic and in vitro evidence
those would go through more testing and hopefully they would turn out to be useful drugs
and even with really good mechanistic evidence one in 10,000 of these compounds that we tried
would work well enough in humans to end up as a successful drug
and the main reason that different compounds would fail was usually lack of clinical efficacy
in other words we know from experience that things with promising mechanisms don't necessarily
work well in actual people
and these drug candidates we were looking at would usually have a way higher level of
mechanistic evidence and convincing animal data which rosemary oil just doesn't have
and that's why properly approved drugs like minoxidil should really be your first point
of call
to get approved as a drug it doesn't just have mechanistic evidence it actually worked
in clinical trials too
I've come across some people saying that rosemary oil can block the enzyme that converts testosterone
to DHT which causes some types of hair loss it's called 5-alpha reductase
and this is really promising because it's how the hair loss drug finasteride works
this is the only study but there are a bunch of problems because everything about rosemary
just seems to be problems
the way the researchers made this rosemary extract that they tested means that it has
very different components from rosemary essential oil which is what everyone on social media
is talking about
the essential oil has mostly stuff that evaporates easily but this procedure means that you get
a whole bunch of stuff that doesn't evaporate and the substance that they think is the active
also isn't found in essential oil
but say you decide you want to make your own rosemary extract using their procedure then
now the problem is they needed 2,000 times more rosemary extract to get the same effect
as finasteride in their enzyme test which just has the enzyme swimming in a test tube
1 mL of 0.25% finasteride is usually used as a scalp treatment per day so if this was
getting into the scalp as well as a really optimized solution of finasteride you would
need almost 5 grams on your scalp and that's about a teaspoon
in the experiment they dissolved 2 mg in 100 microlitres of alcohol which converts to about
a cup of liquid
everyone is struggling to get a 1/4 teaspoon of sunscreen on their face so good luck with
getting 200 times that onto your scalp
they also tested that specific compound and you needed a lot less of that to have the
effect
you only needed two 230 times as much compared to finasteride to get 2/3 of the effect
but the concentration of this in rosemary is really low so to get that 2/3 of the effect
compared to finasteride assuming it gets into the scalp as easily you would have to use
up 2 kg of rosemary leaves every day
so after all of that is rosemary oil worth trying
in my opinion no
for me the lack of clinical trials besides this one puts it back at the bottom of the
heap
there isn't much to support it apart from mechanistic reasons which just don't really
give it a great chance of working and the level of this mechanistic evidence is really
not that high either
there's also the fact that it's a natural product so the levels of any potential active
ingredients in rosemary oil they're going to vary a lot depending on on where it's grown
when it's grown how it's harvested how it's extracted and how it's stored
there are actually three main types of rosemary oil which are named based on what their major
components are
it looks like this study used the cineole version which they aren't really clear about
but even within cineole rosemary oils there is a whole bunch of variation
plus essential oils contain allergens and irritants and these could actually make hair
loss worse
so there are competing mechanisms that could counteract the potential benefits
rosemary has camphor carnosol and cineole for example which have been reported to be
irritating and allergenic for some people
and we can actually see hints of this in the study scalp itching and dandruff actually
increase for the rosemary oil group
scalp itching also increased for minoxidil but again thanks to other better quality clinical
trial evidence we know that any irritation that could lead to hair loss gets outweighed
by the hair growth mechanisms
we know that overall minoxidil doesn't lead to hair loss but we don't know this for rosemary
oil
a side note this study doesn't actually say how they collected this irritation data which
is another huge red flag because a study really shouldn't be missing the methodology for a
full page and a bit of their results
if you do end up trying rosemary oil please make sure that it is diluted
if this study used cineole rosemary oil they diluted it by about 162 times so that is one
drop of rosemary oil per 161 drops of carrier oil or one drop rosemary oil per 8 mL of carrier
oil
it's also worth remembering that hair loss treatments generally are better at helping
you keep your current hair and making it thicker it doesn't really help you regrow dead hair
so the longer you try out less proven remedies and delay using more proven treatments the
worse your outcomes will actually be
so things you should try instead for hair loss
it is best to talk to your doctor or dermatologist
sometimes hair loss is because of an underlying condition or deficiency or allergy and if
you go back and fix that then the hair loss will resolve
and depending on the type of hair loss you have there are often more proven treatments
like minoxidil
if you are going to try rosemary oil it is probably a good idea to try more proven methods
at the same time
sometimes there isn't a reliable solution but it is still a good idea to make sure there
isn't some more serious underlying condition that you're missing
if you want more videos on hair care science you can check out this playlist
if you want a deep dive on how we sometimes know ingredients work even when the evidence
isn't that great you can check out my video on whether retinol is a scam
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