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Consumption of a dark roast coffee blend reduces DNA damage in humans (nih.gov)
266 points by blopeur 32 days ago | hide | past | web | favorite | 160 comments


This study has been supported by Tchibo GmbH, Hamburg, Germany."

Tchibo is a German chain of coffee retailers and cafés known for its range of non-coffee products that change weekly.


Number of locations 700 shops (Germany) 300 (rest of world)

They might want to make some in-store claims about Dark Roast...

I'm generally sceptical of all studies about coffee for this very reason. There's a lot of bullshit studies around food and supplements funded with people with strongly vested interests in selling more product. It's a real problem. For any given supplement, you can often find multiple studies supporting its use and multiple studies saying it's harmful.

When it comes to coffee specifically, if you listen to the studies about coffee, it's some panacea full of anti-oxidants. However, it's a stimulant, it increases cortisol (stress hormone). Stimulants generally makes the body prioritize immediate energy spending over regeneration/healing. There's been a study claiming that caffeine decreases neurogenesis, which should negatively impact both long-term memory and mood.

> you can often find multiple studies supporting its use and multiple studies saying it's harmful.

While true and I get your point, there isn't anything inherently wrong with that. We should expect and welcome research with the awareness of vested interests.

Afterall it's not surprising for a substance to be beneficial in certain ways yet harmful in other ways. Research from opposing groups will help identify all interesting attributes of a substance. Until we learn all there is to learn, you should approach these papers more as additional clues pointing to a certain direction and not anything conclusive about the substance in question.

I work for a biotech company that publishes peer-reviewed science. We use scientific publishing for marketing purposes, to influence the regulatory environment in our favor, and to look better than our competitors. Some of it is done to a very high standard. But in general, doing science with such predefined strategic objectives results in a corpus of scientific output that is hard to interpret. Essentially this sort of stuff pollutes the scientific literature and we should be ashamed that as a society we can't even let the technical content of the scientific literature be free from corporate interests.

I think in the current research climate, you can replace "biotech company" with "university department" and most of your statements still hold true.

Many purely academic studies are done with predefined strategic objectives of advancing one's own prestige, only publishing positive results that fit "your narrative", and indeed polluting the literature with results that are at best incremental improvements, at worst regressions made up to look like improvements.

Are you directly involved in this? If so - how do you justify it to yourself?

(if not then ignore the question - I'm just curious about the mindset of people who do ethically-questionable work)

> free from corporate interests

That won't help. All research is subject to the bias of the researchers. For example, many researchers have been caught fabricating results so they'll get famous. And just because someone is being funded by the government hardly means the government doesn't have a biased interest in the result. Everyone running the government has an agenda that isn't exactly altruistic.

This is funny.

Just a while back there was an article posted about how studies SHOULD start out with defined objectives. The argument was that academics are so desperate to publish positive results that they'll draw any positive conclusion, even if it wasn't what the study started out trying to accomplish.

Indeed. What you are describing is p-hacking


Thank you! I didn't know there was a term for it.

Second that

If p hacking wasn’t so prevalent I would agree with you. Otherwise the researchers funded by MEGA COFFEE will just keep running trials until they get lucky and publish the positive coffee result without mentioning all of the other failed attempts.

>We should expect and welcome research with the awareness of vested interests.

No, we should ban vested interests from funding research studies and reduce the SnR.

Who could possibly not be a vested interest? It's hard to think of more than a few cases where I've personally wanted to learn about something and didn't, at some level, hope for one answer or outcome over another. "Ban vested interests" is an impractical policy. stevenhuang's suggestion to be aware of them is much more practical and has the benefit that "vested interests" who truly do wish to fund an objective study aren't stopped from doing so.

You mean push them into second order vested interest funding?

No, I mean harsh criminals penalties if they can be connected to higher-order vested interest funding too...

GP just means that effectively that's what will happen. just like wow churches push money through think tanks and orgs that donate to political campaigns. The money will never go away it will just get darker and darker and darker.

> There's been a study claiming that caffeine decreases neurogenesis, which should negatively impact both long-term memory and mood.

How much caffeine was required for this effect and how long did it last?

Roasting aka burning the beans seems like it would be a cause of cancer, similar to research about cancer causing agents in the burnt aspects of meat, etc.

I think the cancerous agents in burnt meat are caused by extremely high temps, higher than would be reached in coffee roasting. High temps in coffee roasting could cause the undesirable effect of caffeine break down.

I often see charring on beans. Starbuck's beans are notoriously over-roasted.

Completely - you could also say that reducing DNA damage might actually also decrease immune system surveillance that might be happening causing worse than expected outcomes. Imagine if a lot of cells that might have killed themselves stay alive because of drinking coffee might actually turn out to be a bad thing. We just don't know enough to say for sure and these sort of studies are wildly difficult to get mortality figures from.

We still aren't even sure what general diet is fully optimal long term let alone if one constituent can give actual life expectancy benefits.

So far mortality and morbidity figures say "meh". It is relatively easy to find good quality observational studies with decent power on this exact subject, they're just not sexy so they do not get quoted in pop science magazines.

To some extent isn't that expected?

Let's face it - who would spend the money to fund a study on a substance that's been around for hundreds (thousands?) of years?

Probably if you're going to spend the money to investigate it, you expect some kind of return. So sadly, all these studies end up being funded by people with an interest in a positive outcome.

The bigger question to me is, does that immediately invalidate their results?

The bigger question to me is, does that immediately invalidate their results?

It warrants skepticism of the strongest variety unless the study can be reliably replicated under better circumstances. Don’t be shocked when it doesn’t happen though.

Like alcohol studies paid for by brewers, this is hard to accept at face value given the knowns. Even when money isn’t pulling the strings, nutrition studies are notoriously unreliable by dint of human variability and the nature of the studies themselves.

It depends on the ratio of studies funded vs studies published.

I wouldn't be surprised if around 90-95% of special interest funded studies that aim for a p value of <5% aren't published.

> I wouldn't be surprised if around 90-95% of special interest funded studies that aim for a p value of <5% aren't published.

This is true of the majority of publicly-funded research, too.

> The bigger question to me is, does that immediately invalidate their results?

How many times did they fund this study with different research groups, quietly round filing the results each time until they found a research group willing to p-hack a flattering result?

Yes, I agree, and expect people, companies or whatever to act in their own self-interest, so no implication it is rigged because it may be self-serving. However, I am more suspicious of the study, and studies in general after the recent wave that uncovered an epidemic of unsound statistical methods being used in studies across multiple disciplines. Unfortunately, I am not proficient enough in statistics to vet these things out for myself most of the time, so I remain skeptical, and similarly cliche with the Edgar Allen Poe quote:

“You are young yet, my friend,” replied my host, “but the time will arrive when you will learn to judge for yourself of what is going on in the world, without trusting to the gossip of others. Believe nothing you hear, and only one half that you see."

>The bigger question to me is, does that immediately invalidate their results?

Considering that most such research results are already non-reproducible and p-hacking, the added vested interests land this squarely in the crap category.

People like us nerds thinking it through strict logic ("still this does not necessarily invalidate") might reduce some false negatives, but it mostly just wastes our time and has us taken for suckers from industry/marketing con men. With this kind of "research" taking a shortcut in its evaluation is more productive.

If a YouTuber pulled off this study and vlogged it from start to end, they would make a shit ton of money.

> However, it's a stimulant, it increases cortisol (stress hormone). Stimulants generally makes the body prioritize immediate energy spending over regeneration/healing. There's been a study claiming that caffeine decreases neurogenesis, which should negatively impact both long-term memory and mood.

All true.

Now, by the same token, I am wondering about the effects of decaf. You know, all the alleged "good stuff", none of the sympathetic-nervous-system-stimulation.

Does it have "all the alleged good stuff"? Most of the alleged good effects are in caffeine itself...

If you just want antioxidants (which are themselves oversold too) just eat some berries or something...

> Most of the alleged good effects are in caffeine itself...

I vaguely doubt that.

I mean, this could be tested. Three groups: cold turkey controls, crappy tasting instant coffee group (or even just give them a caffeine pill or something), and full-aroma real coffee group. Groups 2 and 3 get the same amount of caffeine. Now compare the outcomes.

That would be very interesting.

You know how coffee is decaffinated, right?

Edit to address Florin_Andrei's critique: last I checked, the organic solvent processes predominant. Just a gestalt, but I suspect there are some adducts produced and the separation, though evaporative, is still imperfect.

Just something to keep in mind.

I mean I can read this just like anybody with an internet connection


but you'd have to be more specific as to what your concerns are.

It's the same with studies about alcohol. They seem to always fish for some positive effect and ignore all negative effects.

ya they're mostly red herrings. don't forget the impact on our sleep cycles which every day prove to be critically important to our longevity. for a pretty strong and compelling case for sleep (and against anything that gets in its way) -- check out "Why We Sleep" by Matthew Walker.

It's also a typical horseshit vague claim that almost certainly is the result of p-hacking ludicrous meta-studies and other nasty practices. Same as those damn red wine studies that come out all the time touting its health benefits. There's an astounding number of pure trash studies out there.

No, drinking burnt coffee isn't going to defend anyone's DNA. This is patently absurd. Come on y'all, don't vote for this kind of stuff. Shame.

I'm already addicted to your foul dark energy swill, you don't need to sell it to me twice!

I feel this is an instance of "hate the game not the player". Funding of scientific research should always be good, even if the stakeholders are hoping for a favorable outcome. By it's definition science is merely uncovering the truth and can't be swayed.

The reality however where we don't trust the results (especially around nutrition), the issues with replication of studies, and wrong usage of p-values is the real problem. Perhaps we need to mandate replication studies... I'm not sure what the solution is - but I don't feel blaming the industry is the right approach either. Science has the problem here.

I can't access the full text but from the summary it looks as if blood was taken only once. So the difference between one and the other group was not measured before-after and then the change compared, rather a simple comparison was made between the groups at the end. If that's true the whole thing is just bollocks - run it often enough and you'll find a group with this effect.


Hmm. This is why climate change deniers can get a foot in the door....

....the door has been jammed open by skewed commercial interests for decades.

Wow, this sounds like the alcohol industry funding research publications which emphasize that consumption of 2 glasses of wine daily is beneficial to health.

Thanks for pointing it out.

Thank you! What a ridiculous study.

Also the list of authors is a bit interesting. Nothing shocking - but interesting.

Could someone please explain to me how funding could lead to biased results? Is it disbursed conditionally? Is it the desire for future grants?

If it's just bribery, are all of these scientists just selling out constantly?

Too late to edit but I ask this question in earnest.

I have trouble with the notion that we should be immediately skeptical, without reviewing methodology, of any study with industry funding. Some 70% of research funding comes from private entities.[1]

That said, given the current sorry state of "science" (p value abuse, publish or perish, replicability crisis) it wouldn't surprise me if funding related bias really is a common problem.

1. https://en.m.wikipedia.org/wiki/Funding_of_science

Yeaaaaaaah but who else would do the study

Cmon use your head here

Whether its the sugar company or the coffee company, who else would do the study just so some college conspiracy theorists dont make a netflix documentary


Its okay to acknowledge the conflict of interest thats literally what the disclaimer is for, but lets not pretend like a more objective version of this study would have ever happened

> but lets not pretend like a more objective version of this study would have ever happened

Precisely, because a more objective version would have found no effect whatsoever.

If we had even 1 honest meta-analysis for every 10 trials like this, well, we'd know more than we do now. Small trials with inconsistent/poor designs are the bane of medical science.

That said, I drink dark roast so this study must be true.

Here is nice meta study of coffee and cancer risk (dna damage and cancer are probably linked).


> coffee intake was associated with reduced risk of oral, pharynx, liver, colon, prostate, endometrial cancer and melanoma and increased lung cancer risk.

(Heh. Smokers drink nearly twice as much coffee as non-smokers. Smoking increases caffeine metabolism. I think this explains the lung cancer risk)

This is actually mentioned in the study.

To your parenthetical comment: May be unrelated, but totally anecdotal, smokers tend to drink a very light roast that is easily drinkable like a folgers or maxwell house, maybe a coffee shop light roast, like a Dunkin. I don't think smokers are downing cups of Starbucks dark blend and if they are god help their stomachs.

This is probably true in the US, but in Europe I bet you would find that smokers drink espresso (which is usually made with dark roast coffee). Even for "regular strength" black coffee, people tend to drink "americano", which is espresso diluted with water. In the UK, in particular, I'm astounded at the volume of dark roast coffee people drink in the morning.

Any statement like "in Europe" is a fundamental disservice to how diverse Europe is in terms of taste. For example, I don't think I've ever met anyone in my life that likes to drink americano. I know a lot of people that smoke and drink coffee though.

Lighter roasts have more caffeine, because the roasting process damages the caffeine molecule.

I used to think the same, that roasting burns off the caffeine so lighter roast = more caffeine.

But when I looked for a source on that one day it seems like that's a myth. There can be differences based on whether you measure by weight vs volume but that's about it. https://www.kickinghorsecoffee.com/en/blog/caffeine-myths-da...

So now I just say I like light roasts because I like to taste the coffee and not the roast.

This tends to be offset due to the density changes in the bean during roasting.

In short, a cup of light roast and a cup of dark roast have negligible differences in caffeine content.

Medium roasts have the most. With roast, both water evaporation and caffeine pyrolysis increase. Medium hits the maximum. I prefer very light roasts for the flavor.

Dark roasts are easier on the stomach than light roasts as the roasting process reduces the acidity of the resultant brew.

This is clearly the real reason smokers get cancer. They aren't drinking their dark roast.

The real variable isn’t roast its the brew concentration and to a lesser degree acidity, and most coffee I see served “American” style is pretty diluted so that you can see the cup through it.

Is Folger and Maxwell really a light roast? Dark roasts cover up flaws in cheap beans, which I would expect in a cheap brand.

Anecdotally, I knew a smoker once who liked tea.

I drink coffee nearly every day; I am reading this in a coffeeshop. But, p = 0.028? Come on. If you tested for a few dozen things, you would expect to find at least one that had a p-value like that. Was this pre-registered to look at only DNA damage, via this metric? Or did they look at 100 different things to find one with p=0.028?

Of course, if they pre-registered and their theory was that it would reduce DNA damage as measured in this way, that would be a bit different, but from this article it's hard to say.

Now, back to drinking my mocha latte.

The first author has done similar studies with lower p values: https://www.ncbi.nlm.nih.gov/pubmed/24740588 https://www.ncbi.nlm.nih.gov/pubmed/26632023

I'm going to assume that the article doesn't mention a Bonferroni correction and ignore it all.

It's a little annoying if they're cherry-picking but does it really impact the validity of the results? If anything, I'd think they'd have a greater incentive to skew results if they were specifically testing a theory about DNA damage.

"I want to prove that it's good for something, but I don't care what it's good for" is not really a good research question. Then you'll measure 100 things and only publish the one that makes your intervention look good and possibly ignore all the ones that make it look bad.

It's also rather useless if you don't at least have some idea of the mechanism. Coffee has lots of different parts, so what part of it is useful - is it the caffeine? The tannins? ...? And how does it have this effect? Is it even the coffee or just that the coffee group took 5 minutes of rest to drink their brew and that is really the effect?

> "It's a little annoying if they're cherry-picking but does it really impact the validity of the results?"

Yes, that's a well known method of p-hacking.

Yes, p-hacking and related techniques do impact the validity of the results. More on that here: https://info.umkc.edu/drbanderson/p-hacking-and-the-problem-...

The Relevant Xkcd is actually an excellent guide to why this is a problem: https://xkcd.com/882/

Stopped drinking coffee months ago and I have never felt better. Anxiety is down. Sleeplessness is down. General mood is up. Best of all, I no longer get headaches due to Caffeine withdrawal.

When I’m not drinking coffee, I’m less forgetful and think more clearly. I’m less anxious and better in tune with my body. I also feel more myself.

But I love coffee and am usually consuming it. Thank you for sharing your experience. I’ll need to try taking a break soon.

Coffee is life.

I've stopped drinking coffee a fews times. Once while working at a coffee company and there was a full espresso bar across the hall from my desk. Not easy.

The trick for me is maintaining the ritual. Tea fulfills that need in me. First to black & green and then to herbal.

Happily, I've learned so much about tea, I love it nearly as much as coffee.

You're welcome!

The taste of coffee is pretty tough to resist, I'll admit!

They do make decaffeinated coffee, although I've never tried it myself.

I have switched to decaf espresso (for pretty much the same reasons as outlined above). It does not taste as good, but it is close enough - so it is a satisfactory substitute for regular espresso.

I’ve had some success by mixing in a minute amount of baking soda into the coffee immediately before brewing. Probably works best for French press. Literally the smallest amount I could get between my thumb and finger. Ie 1 mg might be more.

Apparently, decaf still contains about 25% of the normal level of caffeine. I read this in the "Why we sleep" book by Matthew Walker, but haven't double checked.

Basically, that would mean that drinking decaf is not really the same as not drinking coffee.

i also love coffee, so i do periods of decaf-only to re-balance my caffeine tolerance. decaf doesn't taste good by itself, but milk and sugar (which is how i usually drink coffee, whether espresso or not) tolerably dampens the inferior taste.

Caffeine addiction can hit you hard, but withdrawal should be done after just a few days. So give yourself two weeks!

The problem with these type of comments is that they never mention how much coffee, and what type of coffee, was consumed before the life-changing decision.

It is pretty much anecdotal evidence.

Agreed, it is anecdotal.

But for the record, I drank about 500ml of coffee per day. About a full single french press container.

I certainly drank a lot less than most people who swear that they felt fine drinking 5x as much as that per day... with some even claiming that drinking it just before bed helped them sleep.

I've found what was really bad, at least in my case, was drinking it every day. I was just insidiously sliding towards a state of perma-depletion.

Drinking it occasionally seems fine. As long as I think of it as a treat, it's not too bad, and may indeed help actually.

How do you define perma-depletion?

Tired all the time.

Was quitting coffee the only change you've made in your lifestyle? Or did you e.g. started working out, be more strict about your daily regime, be more careful with what you eat?

It was the largest single change, yes.

I have always eaten healthy food, I go for walks and hikes and bike rides regularly but I wouldn't say that I "work out".

I just developed a massive headache one afternoon, realized it was because I hadn't had my morning cup of joe, felt disgusted with myself as a result, and decided to quit drinking it altogether.

I figure that anything as addictive as that has no place being consumed daily.

I grew out of my nicotine habits and other addictive drug habits years ago for the exact same reasons.

But was it worth all the broken DNA!!

Well, I quit drinking coffee 3 years ago and I can confirm all this. Before quitting I drank approximately 3 mugs of coffee per day.

Withdrawal symptoms for me were a really bad migraine for one whole week and that actually made my final decision to never start drinking coffee casually again.

However, as I try to avoid all kinds of absolutism, I enjoyed a small cup of campfire coffee last autumn.

For some reason drinking tea doesn't make me anxious or tense.

I like to believe the calmness from tea comes from L-theanine, commonly present in tea leaves. https://en.wikipedia.org/wiki/Theanine

However, experimenting with putting theanine in coffee and consuming energy drinks with caffeine+theanine aren't as relaxing, perhaps because of the higher caffeine content, or other relaxing compounds in tea.

I drank about 40oz of coffee a day, and had the same symptoms if I stopped. I started replacing coffee with tea and the symptoms were a lot less severe. I'm now down to about 1c a day of coffee I grind and brew myself, as if it's a hobby enjoying the flavors and characteristics of different beans/grinds/brewing methods, not because I need caffeine to be a functional adult.

> Sleeplessness is down.

Curious when you got your last cup of coffee usually time-wise. E.g. I stopped drinking coffee after noon, my sleeplessness went down and consequently all other symptoms you described. And maybe I reduced some DNA damage by continuing drinking at the morning :-6

I really hate bad science, and this is an example.

Springer Science+Business Media (the publisher) does not transfer copyright of the paper from the author to the publisher like many other journals. This begs the question, why isn't this article open access? The primary author, Dorothea Schipp, is a statistics consultant in small town Germany [0] not associated with a University and the blood work was done in Slovakia. No PHDs or MDs among them. [1].

Digging deeper into their research method [2] the study looked at DNA breakage over a four month period in blood sampling for a coffee and non-coffee/caffeine group. I have a few questions about this, mainly around how effective the time period and method for determining total DNA stability. How many individual cell gnomes were measured in the before/after? What's the random variance for genome variability among cells in the same body? I suspect the variance is high enough to explain their unbelievably low p.

My guess is that the statistician is having fun with p-hacking [3] while collecting some funding from industry.

[0] https://en.wikipedia.org/wiki/Rosenthal-Bielatal


[2] https://www.mdlinx.com/journal-summaries/coffee-comet-assay-...

[3] http://psychology.wikia.com/wiki/P-hacking

Also the study was ordered by Tchibo - a producer of dark roast coffee. What a coincidence. So naturally they didn't have an interest in finding that (assuming that the result is valid at all - which I doubt) tea with caffeine (or maybe just caffeine pills) has the same effect. Also why did they use a blend on earth? This study doesn't make sense on so many levels. But nobody diggs into it so it's successfully feeding the nutrition misinformation circle jerk.

As you have access to the paper - do they take blood only once and compare the groups or do they they take 2+ times and compare the change? With such a small sample the first option would be very dubious.

Right. At root, the protocol was not published and the outcomes were not prespecified, ergo this is dogshit.

Quick googling indicates that tea has similar effect https://www.ncbi.nlm.nih.gov/pubmed/24585444 (very small study but effect size is good), another study is https://academic.oup.com/jn/article/138/8/1567S/4750818

What are the common ingredients in coffee and tea except caffeine?


It seems like black tea also, although I can't make sense of the biological jargon. https://pubs.acs.org/doi/abs/10.1021/jf010875c

Individual studies can't tell you too much. Eg there was a rather solid study like tea to throat cancer risk with the analysis that it might have been due to the drinkers drinking tea at very high temperatures, rather than the actual content of the tea.

In this case, what really made the effect? Maybe the coffee group was just more likely to take a break (de-stress) or walk an extra flight of stairs to get the brew!

Why couldn't caffeine be the main mechanism-of-action?

It's a diuretic, so those treated with coffee likely drank more total liquids during the study, and perhaps flushed more older/damaged cell material.

Not a biologist or a doctor, but I'm pretty sure you don't pee out damaged cells.

I was referring to the products of cell degradation. Autophagy – destruction of cell components or full cells – is a constant, natural, necessary process. Its waste products have to go somewhere, and biomarkers related to autophagy, and all the other waste-eliminating functions of the kidneys and liver, can be detected by byproducts in urine.

It's also the case that full red and white blood cells, and epithelial cells, are found in urine, and at higher-than-trace levels in various disease states... but that may just be incidental to kidney/urinary tract functioning.

Still, more peeing from regular use of a diuretic like caffeine, and commensurate higher water intake, is going to mean more flushing of anything unwanted in your blood, like the broken DNA strands detected by this study.

Which raises my question: is there really less DNA damage, or has the detectable evidence of the damage just been swept out more rapidly?

My semi-educated guess would be that kidneys work best when the volumetric output is average. These are not 100% passive systems like coffee filters, they have some active filtering mechanisms. If you overwhelm them with fluid intake, I would suspect they start to underperform.

Both contain tannins. I am not suggesting that these are the cause of the benefits observed in the study.

Beer contains tannins also. Not that I need any extra excuse..

Old school leather may be infused with tannins. Should I start licking those boots now?

Steep them in some hot water and serve with cream.

To what extent are "DNA strand breaks", as measured in a blood sample, correlated with other health outcomes?

Caffeine is a diuretic. The coffee group likely consumed more total liquids in the course of the treatment. So the mechanism might be simply more flushing of damaged cells – possibly beneficial, but not unique to coffee.

It's odd for the headline to highlight "dark roast" when lighter roasts weren't tested, for comparison.

Hypothesis: they tested both dark and light roasts, the light roast showed no effect or a bad one, hence this study. Just an hypothesis, I have no data to back that up.

I'm surprised (horrified?) that a control group's DNA deteriorates significantly enough in such a short trial to use as a comparison. #entropy

The study is likely useless since eight weeks total does not constitute long-term effects. You’d need to do this with a larger sample size over years to get reliable data.

8 weeks is not unusual for a study like this (randomized and controlled). Almost no study where researchers tell participants what to do will be longer. Epidemiological studies, of which there are many on coffee, do have more subjects over years, but rely on self-reported data.

Central Europe. Maybe they took the 50 or so older people still living in the Tschernobyl exclusion Zone?

I wonder if they took fast vs slow metabolizers into account. It seems to be healthy only with the fast metabolizers gene:


If you’re a slow caffeine metabolizer:

1. Increased risk of high blood pressure (hypertension).

2. Increased risk of heart attack.

3. Higher chance of digestive disorders.

4. More stress and measurable cortisol spikes.

If you're a fast metobolizer:

1. Longer life.

2. Faster metabolism.

3. Better memory and mood.

4. Lower cancer risk.

5. Better blood sugar + insulin balance.

I'm most assuredly a slow metabolizer since caffeine makes me feel terrible.

I'm a bit confused by the linked article. The only link to a study I found was to [1] published Advances in Psychiatric Treatment. The other study quoted is for some specific effects the article mentions. Any idea where the link between CYP1A2 and caffein comes from?

[1] https://www.cambridge.org/core/journals/advances-in-psychiat...

Hey guys Pub Med Labs developer here. Check out this very same fascinating article in the new Labs site and please give us your feedback! Much appreciated.


The increased white space and font size make it much easier to read. Responsive layout for mobile phones. Overall a much better experience. Thanks!

Looks good. Could you move the doi towards the top? I would rather not scroll for it.

It looks like the future. Thanks for the hard work on this. Great job!


Figure 2: The coffee-treated group is anomalously higher in the quantified metric BEFORE the treatment. This is entirely an artifact of stratifying the treatment vs. control group prior to wash-out. The only significant difference is between all groups and the PRE-treatment coffee group.

While the research may be compromised by a conflict of interest, I still have a legit question.

Trader Joe's discontinued my favorite dark roast coffee (Fair Trade Organic Guatemalan) and nothing I've found has come close to the taste and cost.


Does anyone have a suggestion for me that's ~$10-$12 per pound?

Have you tried Peet’s Big Bang? It’s medium roast but definitely has the flavor of darker roasts.

Haven't, no, but I'll swing by and see if I can try a cup. Thanks for the suggestion

> consumed 500 ml of freshly brewed dark roast coffee blend per day,

half a liter per day of coffee is a lot! I wonder if they controlled for caffeine

some highlights from my reading:

- 372mg caffeine per day

- water-only group specifically avoided caffeine

- coffee/caffeine group had to abstain from all caffeine for 4 weeks before study (baseline to 300+mg a day is a LOT for someone with no tolerance)

- they base their claim of the 'darkness' of the roast mattering on other similar studies, with less pronounced results, that used lighter roasts.

"Among several previous studies of the effects of coffee consumption on DNA damage, only two were randomised controlled trials, with DNA breakage rather than oxidative modification of DNA bases analysed [23]. Bakuradze et al. [14] also studied the effects of coffee C21 consumption, after 4 weeks of intervention, and found a decrease of DNA strand breaks by 27% in comparison to the control group with water consumption (p<0.001). Misik et al. [22] studied a much shorter intervention period (5 days) and a different coffee type and used isolated lymphocytes. In comparison to C21, the coffee had an approximately twofold content of caffeoyl quinic acids and trigonelline and about half of N-methylpyridinium. Therefore, the coffee used by Misik et al. is a light/ medium roast type while we used here a dark roast blend. We assume that the different degree of roasting accounts for the different outcome observed. "

It's 2-3 typical cups of coffee... 2 in the morning and one later in the day. Now, if it's laced with a ton of sugar or "sugar free" sweetener that metabolizes like sugar, that's different.

The first thing I notice is that both the first and last authors of this paper are industry-affiliated. Not to say there's anything inherently problematic with that, but at least raises an eyebrow about the motivation behind this study.

Too bad dark roast coffee also triggers a bunch of digestive tract ailments. Other than stomach ulcer, hemorrhoids, and all the bowl irritations, dark roast coffee is just fine. Noooooooooooooooot.

I'm willing to bet there is another study that coffee causes some sort of cancer (last I saw it was linked with colon cancer). I'll still drink my coffee, and tea, and probably continue to consume nicotine in one of many forms.

Life is too short to worry about maybe, probably is something you should likely worry about - that why I stopped inhaling burning things to feed my nicotine addiction, while cancer isnt all that likely, COPD, heart failure, and others issues sure as hell are.

Amongst other effects not stated in this study

While I'm always happy to hear good news about coffee (although as an espresso aficionado, I'd be hard pressed to consume half a litre a day), given the obvious difference between coffee and water, I don't see how this can be a 'single-blind' study.

Yeah, this is bullshit.

100 people were a part of this "controlled" study.

Please don't be one of those people that runs around telling people this. This is nothing more than biased surveying by a weak company in attempt to create self-promoting propaganda.

Thank you @1_over_n for doing the research

100 people can be enough. Single number like N is not going to tell much.

People should learn the basics of statistics before they start to have opinions.

...or the basis of where funding comes from? I think you missed what the parent was alluding to.

In what world would 100 people be enough to represent anything accurately enough to make a generalized claim like this? All I know from the article is that there were 50 women and 50 men involved. It says nothing of age, fitness, dietary regimen, etc. Based on the "statistics" provided, I could equally make the claim that "drinking a warm drink reduces DNA damage".

Also, please don't generalize "people" in your backhanded comment. I recommend that you study up on critical reasoning. Maybe then you would come to understanding that most "statistics" are unintentionally (or intentionally) biased, and are therefore bullshit, and not to be taken at face value.

I criticized your backhanded N = 100 comment because it's silly.

Your comment "In what world would 100 people be enough" shows your disbelief in basic statistics.

In typical well conducted study N=100 participants is close to the minimum sample size when the population is large.

No statistician says that N = 100 is not enough to represent things accurately without knowing other parameters and the design of the study. With large enough effect size N=1 is more than enough and. N = 1800 is enough even if the population size is infinite in the optimal case.

You've got me there. I believe most basic statistics are deterministically useless.

I asked 3 people if they agreed with me. 2/3 said yes. So I guess I'm right

I grew skeptical the moment I read "single-blind" test. So, the researchers know which group is what and that could involuntarily lead them to pick for what they are leaning to find (given it is funded by a coffee company)

Odd days: research shows coffee is good for you

Even days: research shows coffee is bad for you

It's both good and bad for you depending on which health indicators you look at. People tend to treat "Coffee prevents cancer" and "Coffee raises blood pressure" as if they contradicted each other but really they don't. The whole thing is very dose dependant too. Correlationally life expectancy maxes out at around 3 cups per day but I doubt that's the causal maximum.

I don't buy it. I love coffee and caffeine in general but it's just a stimulant.

I personally believe the net effect is to make your body work harder to get through the day.

I think it's bad unless you were funded by the coffee industry.

Even if being a stimulant were its only property, what makes it decidedly bad? Researchers understand it as a stimulant as it is, they're not evaluating its worth "despite" being a stimulant. If consumption in small doses poses a net harm for that reason, there ought to be stronger consensus, which is lacking.

I mean more often than not, news touts the good side. What's thought to be negative anymore, aside from cafesol which can be filtered?

As a stimulant coffee could be placing stress on the body leading cells with damaged DNA to act more aberrantly and subsequenttly rejected by the body.

"The study comprised two periods of 4 weeks: a preconditioning period, with daily consumption of at least 500 ml water but no coffee, nor tea, nor any other caffeine-containing product. During the subsequent intervention period the coffee group consumed 500 ml of freshly brewed dark roast coffee blend per day, the control group consumed water instead."

Apparently, it's caffeine, or perhaps hot beverages (as it doesn't seem like the control drank their water heated).

The information that would help me is an answer to the question: Why?

... and increases problems with X,Y,Z I wouldn't be surprised to learn, before anyone thinks about taking this as health advice.

Coffee remains one of the few things you can buy the best of, in the world, for less than $100usd and enjoy for several days.


Only grind what you are going to brew immediately. Use a conical Burr grinder. Technivorm coffee machine else bonavida.

If this is true, my DNA is so healthy.

All I can say... "Is Most Published Research Wrong?" https://www.youtube.com/watch?v=42QuXLucH3Q

TL;DR: Likely yes. Spinning statistics is not that hard, even with the best of intentions.

Can't see any evidence with "n=50"...

I have a simple rule in my life: Anything that is addictive is harmful to us. Coffee falls in that bucket.

You're going to need a bigger bucket then.

The problem with simple rules is it removes all nuance. For example, when smoked tobacco is extremely addictive and therefore harmful according to you. But then you would ignore all the other practical, medicinal uses that tobacco has when used with wound dressing and pain relief.

Of course that's not a perfect comparison to coffee and caffeine, but just because you've got people hard-addicted to Starbucks lattes and espresso doesn't mean caffeine is flat-out harmful to us all.

Watch out for carrots[1]. Lots of non-addictive things are also harmful, of course, but I suppose that doesn't by itself invalidate your principle. In the case of coffee and tea it seems possible that the benefits outweigh the harm.

1: https://journals.sagepub.com/doi/abs/10.3109/000486796090626...

simple rules aren't always good

Good. I will continue drinking French Roast then.

hhhhhhmmmmmmmm 4 weeks only?

>Our results indicate that regular consumption of a dark roast coffee blend has a beneficial protective effect on human DNA integrity in both, men and women.

What they established was that drinking water damages DNA. When they drank coffee there wasn't as much damage. It's a stretch to say that coffee is providing a protective effect though.

Without denigrating anyone, it's a bad study.

What was the chemical breakdown of the water? Was it tap water? Distilled? Bottled? Spring? etc.

A better designed study would have groups drinking different kinds of water. Was the fact that the water was boiled (in the coffee) providing the protective effect? i.e removing toxins etc, did the kettle they use have a filter that processed the water, whereas the water was drunk straight from a tap etc.

Coffee is great though!

Coffee contains water. If water is harmful, coffee will be just as harmful unless it has protective effects.

In any case, you can't say they "established that drinking water damages DNA" and then go on to argue that they should establish it with another study about water.

It's not clear to me that the control group drank 500ml of boiled water.

If they're drinking cold tap water, it could be that the act of boiling the water yields the desired effect. If they're drinking bottled water (and if the instructions said "drink 500ml of water", this would be my first inclination) then maybe the DNA damage is being caused by plastic that's leaching into the water as opposed to any preventative effect in coffee.

If it's the plastic, then we need follow up studies comparing people drinking coffee in plastic cup vs paper cups vs other non plastic non paper glassware!

I don’t think it’s the cup that leeches plastic, unless it contains BPA.

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