Comparison of Postsurgical Scars Between Vegan and Omnivore Patients | Hacker News Reader

Comparison of Postsurgical Scars Between Vegan and Omnivore Patients

pubmed.ncbi.nlm.nih.gov

115 pointsshadykiller108 comments

When I was younger and training very heavily in some sports, I experimented a bit with different diets. Bottom-line the more meat heavy my diet, the faster I would heal from injuries -- radically so. For a while I went on a low-carb diet and ate a very heavy animal protein diet. I shed pounds, had absolutely unstoppable stamina, had far fewer injuries, stretching improved, basically never bruised, and healed from sports injuries that would have taken weeks in days. I felt like Wolverine.

I also felt like a grease grenade all the time and got tired of the diet which is why I stopped, but it was definitely superhuman for me.

I felt the worst in this sports context was when I experimented with a vegan/vegetarian diets. The effects were virtually the exact opposite. I'm sure with a nutritionist and more dedication I could have overcome many of these issues, but I found building a decent diet harder and required more effort.

I found similar results when I tried a vegan diet. Like you, I suspect that I could have made it work if I spent the effort to figure out what was missing. If I actually lived my life according to my personal ethics that's what I'd do.

For now I've found vegetarianism significantly easier and a satisfactory compromise between ethics, health, and nutritional laziness.

What do you mean when you say you felt like a grease grenade?

Just very very greasy out of my pores. Oily all the time, 2 or 3 showers a day to keep the grease out of my hair. That sort of thing.

Did you ensure that you maintained protein level when you went vegan/vegetarian? It's easy to eat much less protein if you aren't careful.

I tried to but I'm very sure I didn't balance my macros the correct way at the time. I tried to eat lots of soy protein powders and things but have some kind of bad reaction to too much soy for some reason. By that time I had lost interest in eating that way and the noticeably negative effects on my sports training made me go another direction.

I lift heavy about 4x week.

A lower-carb calorie-restricted diet makes me more alert and focused. On the other hand, I sleep like shit, my anxiety levels skyrocket, and I also feel moodier, particularly in the mornings. I also lose strength fairly quickly.

Eating at a surplus with carbs makes me more lethargic, lazy and less focused, but I sleep far better, and I’m in a happier, more social, mood. And of course I can make strength gains.

I tried surplus keto a while ago but didn’t enjoy it and didn’t see any of its touted benefits.

If I found a diet that was all positives like you described, I would probably hold on to it with my dear life.

What did your it consist of? Did you eat at a surplus or a deficit? And what made you quit?

This is going on 25-ish years ago, but it was basically the Atkins diet. I didn't monitor calories in any way, but I lost about 35ish pounds eating that way (and exercising). I stopped because it was getting boring eating that way and I felt really greasy all the time. Plus it's kind of expensive and I was a poor college student.

Seems normal carnivore diet to me. Check out Shawn Baker for more.

Animal protein seems to be good for wellbeing, and there's a lot of overlap between veganism, wellness awareness, and alternative food choices.

Given that and the already-existing ability to create collagen/gelatin in a lab that's suitable for vegans, I've always wondered why nobody has managed to get it to market as a food.

There's already a growing group of wellness-focused people who don't want typical non-gelatin jelling ingredients like carrageenan and various gums in their foods; these provide only the jelling property and none of the nutrition of actual gelatin, and they are associated with inflammation.

Edit: Maybe all of the funding is going toward grail projects like synthetic beef patties that have an element of technical novelty, rather than the comparatively boring process of creating collagen at scale and getting FDA approval?

> Given that and the already-existing ability to create collagen/gelatin in a lab that's suitable for vegans, I've always wondered why nobody has managed to get it to market as a food.

Outside of some pastry applications (eg. mirror cake glazing), it's pretty much only used for Jell-O and aspic, neither of which are particularly trendy at the moment.

There's gelatin and collagen in soups as part of making broth, but it's not really something that people see as an ingredient.

Huge demand for collagen powder as a beverage additive lately though. Could definitely be a real opportunity.

For example, Nestlé purchased "Vital Proteins" last year and are making their collagen products to their Nestlé Health Science portfolio.

https://www.fooddive.com/news/nestle-to-acquire-majority-sta...

When I was last in the USA, I was very surprised to discover all the yoghurt in the store I went to contained gelatin.

This is a consequence of the low-fat craze that peaked in the 90s but still exists. When you remove fat from yogurt, you need to add sugar and gelatin back in so it has flavor and texture.

That said, you should be able to find plenty of real yogurt in the US now.

Ah, you may not be aware of this. Collagen supplements are trendy with the wellness crowd as a protein powder, and bone broth is too under closely related reasoning. People who buy these things are thinking, "I want my skin and tissues to be healthier, so I'm going to buy collagen or bone water that is full of it."

This study seems like it bolsters the reasoning. The market for both of these options is currently closed off to vegans.

IIRC from back when I was a vegan, and assuming what I heard was correct at the time, there was a single, very popular foreign supplier of "vegan" gelatin that was eventually exposed as a fraud. The gelatin they were selling was of animal origin. There were no competing products. Any new product will have to overcome the residual mistrust from that incident.

Found a source for the story that matches my recollection: https://aaww.org/the-vegan-marshmallow/

I've actually noticed this effect on myself too. It's very pronounced in fact.

I have a bad habit of biting my cuticles. I also happen to observe lent, effectively going vegan for 50 days every year.

Typically my cuticles heal the next day, or two at most. But every single time I enter lent, suddenly my cuticles take more than a week to heal the same amount. The difference is very obvious, to me at least.

curious what kind of lent you observe that's for 50 days not 40.

If you count Sundays, it’s closer to 50 than 40.

i see, so apparenly different traditions count it differently. i had always heard of it as 40 days of lent or cuaresma etc... didn't know it could go upto 46 days.

Gonna be orthodox christian for sure. They do the vegan diet for lent and have a few extra weeks at the beginning. The extra weeks have slightly different rules and technically aren't part of lent but it amounts to about the same thing.

Grew up in a family that did this and still do it because I like the structure and changes through the year.

> This study suggests that a vegan diet may negatively influence the outcome of surgical scars.

This is unusually damning to veganism-as-it-is-practiced if not to veganism itself. It would be interesting to see these results across a wide range of diets.

Agreed that there are probably ways to remediate some of these effects.

I definitely favor smaller less impactful scarring, but also, so what? Calling ths "unusually damning" seems like a significant overinflation of concern.

For all we know, it may have far more significant pro-recovery characteristics associated with it. "Oh you built too much scar tissue? Your vegan diet also stitched your blood vessels back together really well."

dang really needs to get YC to develop an AI that can automatically add /s to ironic comment.

I'd rather HN not allow such comments and we try to make debate here better than on the rest of the internet.

Or people could work on their ability to identify normal human modes of speech.

Given we’ve had the internet for over a generation with this issue being known that whole time, I don’t think that’s actually something we can do. Not in general, not from plain text.

I think only morons, autistics, etc have a habitually hard time identifying sarcasm. These are not the people we should optimize the web experience for.

Only when spoken, not when written: https://theconversation.com/why-is-sarcasm-so-difficult-to-d...

No, I have zero problem detecting sarcasm or irony in text. If you think about it for 5 seconds it's usually pretty clear.

If you have zero problem, you are unusual.

Please note who wrote this paper, considering what they are famous for, as well as the results: http://web-docs.stern.nyu.edu/pa/kruger_email_ego.pdf

Text inherently makes it difficult if not impossible to distinguish sarcasm that would be apparent with verbal/visual context clues.

One of several motte-and-bailey tactics used by vegans is going from

“Veganism is healthy”

“Veganism can be healthy if you exercise an impressive amount of restraint, discipline, and judgement in your vegan diet”

_If_ you can get enough exercise, you can be healthy on pretty much any omnivore diet because it's so hard to not get enough nutrition, and extra calories don't matter if you burn them off. I personally lost lots of weight when I was cycling regularly to work and school (10km and 50km round trip respectively), as well as caving and climbing on weekends. Almost everything I ate was fast food, because I had hardly any spare time. But I was definitely healthy and felt great so long as I took enough days off (I was getting enough exercise that I simply couldn't do it every day).

Meanwhile, I know lots of people who have given up on vegan diets because they felt like their health was declining, even with regular exercise. I'm sure with enough care and nutritional science they could have gotten it to work. But it's so much easier to just add some animal products to your diet.

I remember hearing the question asked someplace about whether any professional athletes are vegans, especially for the intense sports that require a lot of muscle rebuilding and maybe even contact sport healing and what not. That might illuminate things a bit.

There is an advocacy* movie called The Game Changers which highlights several vegan athletes and makes the case that their plant-based diet contributes to their success. https://gamechangersmovie.com/

* I would not consider it a documentary as it has a clear agenda, but I found it interesting nonetheless.

https://www.lonesomelands.com/new-blog/2019/9/16/t2amoscp1u1...

that guy may be able to make a statistical argument with this sort of data. Number of injuries and percent of time on the bench with the two pools and a simple t-test or something.

> This is unusually damning to veganism-as-it-is-practiced if not to veganism itself.

I don't think a sample size of 21 is especially damning. Nor do I think that the study's authors would come to that conclusion either.

Depends. Emotive language aside (i.e. "damning") the low sample size is actually "more evidence" in the presence of a convincingly low p value.

It means that this particular sample of 21 people would have to be extremely atypical under the null hypothesis of no difference. Therefore, given its low sample size (and thus wide standard error), it is 'some' evidence that the effect size is also probably quite large.

That doesn't sound right. The reason sample size is important is because the larger the group, the less likely the group is to be atypical. I don't think you can turn that around and then say "this group is small, which itself is evidence, because otherwise it would have to be extremely atypical to show a difference." That's completely circular.

The p-value is still the important thing because the p-value is itself affected by the sample size.

No, effect size very much informs all of that.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3444174/

> the larger the group, the less likely the group is to be atypical.

Not true (unless I misunderstood what you were trying too say). The probability that a sample will be atypical under the null is exactly the significance level, and does not depend on its size.

What does change with size is that the distribution around the statistic gets more concentrated, meaning your threshold moves to the left, towards lower effect sizes.

Which also means that for smaller sample sizes, it is harder to reach significance, unless you're dealing with a fairly large effect size.

I'm not sure any of the vegans I know would give up veganism in order to minimize their scars any more than the meat-eaters I know would give up meat based on studies that show it can be mildly unhealthy.

Maybe I'm reading into it too much, but the outcome of this study seems to suggest there may be other healing-related issues attached to veganism.

I wouldn't be surprised, though I would be similarly skeptical that other healing-related issues would sway people one way or the other either since (at least the vegans I know) don't adopt the lifestyle for health reasons.

Very large effects are unlikely given the number of long-term vegans who seem to maintain sufficient health. Whereas small effects might be considered a worthwhile sacrifice.

Agreed as a vegetarian, this study being called damning is a joke. Veganism has a pretty good track record with respect to health outcomes. Committed vegans that I know would still do it if it lowered their lifespan, because they are doing it for a higher cause (environmental, moral, spiritual, etc.)

I reject your premise that eating meat makes you “mildly unhealthy”

Exactly.

[To clarify: I am not qualified to judge the general healthiness of any particular diet -- any sufficiently popular diet seems to have conflicting studies showing it is "healthy" and others showing it is "unhealthy". The point I intended to make above was that most people either outright reject or remain unswayed by these kinds of studies.]

"Veganism" denotes an ethical stance, despite the plant-based health foods movement co-opting the label, or some activists (ab)using health claims to promote a vegan diet. A study about scar tissue is in no way "damning" of it.

What's the point of having a better looking scar if you're more likely to get colon cancer?

Also, given that study itself measured Iron and B12, supplementing Iron and B12 may help scar healing w/o the (red) meat eating downside.

> What's the point of having a better looking scar if you're more likely to get colon cancer?

I don't think it's worth going into the extremes with this. Omnivore doesn't mean a buttload of red meat.

I'm curious here: I am under the impression, possibly due to outdated info, that the issue with red meat was specifically that cooking it at high temperatures creates carcinogens (this being why bacon is especially bad). Would it be possible to avoid carcinogens by slow cooking all red meat at lower temperatures?

Attributing colon cancer to meat is, it turns out, complete bullshit, just like most other nonsense anti-meat fear-mongering (uric acid, cholesterol, etc.).

I'm not familiar with the data either way, so am reading to learn; why do you say it's bullshit?

In context, I think it’s as fair to call it bullshit as to claim it as a truth.

It was being claimed as a truth to rebut the implications a peer reviewed study, but without any data to support it.

Every time I get concerned about one of these things and look it up, it turns out to have been false.

I have the same experience when apparently anti-vegan results/studies appear on HN. Usually the headline is a million miles from what the study could claim to show. It would be nice to actually see this paper.

This was the last time I looked at one of these claims: https://news.ycombinator.com/item?id=23661158 (Article claimed 25% of vegans have low blood iron, and the study involved ..10 vegans.)

Before I became vegetarian I read as many papers as I could about why meat is good or bad for you.

Unfortunately a lot of papers don't provide very good data regarding what kind of meat is being eaten. At least, not in what I've read; I'd love to see something better.

Some very specifically included processed meats which, to me, invalidates the study as a study about meat. Processed meats are a completely different beast. On those grounds a significant number of studies I've read are hard to take seriously.

This could be a reason people are calling it bullshit.

I'd love to see a study involving conscientious meat eating habits in which people eat mostly vegetables, some whole meats, and otherwise avoid processed foods. This is how I'd want to eat if I ate meat, but it's rare to see balanced studies.

This does, however, make some sense: most people eat processed foods where these studies are done, so they're relevant to a broader part of the population.

They should not be used to condemn meat, though.

> Also, given that study itself measured Iron and B12, supplementing Iron and B12 may help scar healing w/o the (red) meat eating downside

Unless iron is the source of the (red) meat eating downside.

It's not even clear what's meant by "red meat". In all the studies they mix up consumption of unprocessed and processed meats. In my totally non-scientific metastudy I came to the conclusion that it's essentially processed meat with nitrates that poses the major health threat.

Note how the study compares vegan diets with omnivore diets, not with salami and bologna diets.

Personally I think that a good, healthy diet is one that does not require me to take supplements to counter deficiencies.

Obviously that does not mean that eating a lot of meat is good, but having to take supplements is not good, either.

Others already said below research on red meat and colon cancer correlation is imperfect. It not to distinguish processed meats with not processed. It not consider for difference in cook methods producing potential carcinogen, say grill vs. bake. Also many people maybe are not predisposed to colon cancer, they prefer to have better healing and take a risk such like that.

Also study is compare of vegan. Not veggietarian. This mean potential beenfit from dairy. ALso potential white meat not reds. You have made a link from red meat to scar outcome where above study no created one. This is bad thinking.

Also you are say for supplementing remedy all problem on vegans. This supplements expensive need much research. Maybe hard for getting right. Why benefit from this and use vegans diet? If same results are come from meat. There am also chance for benefits not iron and b12 related but maybe collogen and other meat things.

Iron and B12 seem like obvious avenues to explore here. Anemia in particular is very common among vegans and vegetarians, since it takes a good bit of care to reach optimal iron levels without consuming heme iron or supplementation.

> Conclusion: This study suggests that a vegan diet may negatively influence the outcome of surgical scars.

> Twenty-one omnivore and 21 vegan patients who underwent surgical excision of a nonmelanoma skin cancer

Interesting, but its a small group and stats are on the low end?

n=21 is not necessarily a small population from a statistical standpoint.

Anyway, would be interesting to get comments from doctors who trest vegans. I'm not surprised at the result (we are what we eat), so perhaps vegans really should be on vitamins.

This journal isn’t open access is it?

I wanted so see the effect sizes not just p values which are unhelpful. But if the vegans are all vitamin b12 deficient, it’s not a surprise their health has consequences.

And my other question is, is there self selection going on. People who go to hospitals have worse outcomes than people who don’t, so the best thing to do is to avoid hospitals. P < 0.001. Right? No, wrong. Did they become vegans due to digestive problems or other health issue?

I’d really like to read the article to see if they considered these things.

Strange way to word the two patient types: vegans as opposed to omnivores. Vegans are still omnivores, they just stopped eating animal products because of beliefs.

I also smelled once a vegan cake. It's a medical miracle they can survive on such a diet.

> Vegans are still omnivores,

No they aren't.

From New Oxford English Dictionary:

> omnivorous

> adjective (of an animal or person) feeding on a variety of food of both plant and animal origin.

Herbivores are reciprocal to omnivores. Vegans are not comparable to either. Vegans don't eat animals not because they can't, but because of their beliefs. The word vegan describes a belief, contrary to omnivore and herbivore that describe physiology.

A human may choose to walk on all fours because they're insane, but they will still be a biped.

That's not how language works.

As much as the results of this study confirm what I would expect, keep in mind it was an observational study and not a controlled experiment. There might be some other factor at play in the vegan group, say, other than just their diet.

Unfortunately I imagine an experiment to further investigate this would be hard to get past an ethics board. I.e. wounding the participants to see the effect on scar formation...

I would like to see a comparison between the top 10% vegan and omnivores. Most vegans are clueless when it comes to making up deficiencies in typical vegan diets.

Glycine is one of the relevant aminos that is very suboptimal or even scarce in vegetarian and vegan diets. It is also going to be one of the important (and likely most common) limiting factors in tissue repair.

Proline is also needed for collagen production, but not as deficient in Glycine as far as vegetarian diets. Glycine is also highly water soluble and a small molecule; it is constantly lost in urine. The need for glycine goes way beyond collagen production. It is essential for so many biological functions.

Glycine is not considered an "essential amino" because the body produces glycine itself, hence it is overlooked by many. It turns out the body produces only enough to usually barely scrape by. My guess is if another group of vegans were given Glycine (at around 4 to 5 grams/day) supplementation the disadvantage relative to omnivores would be erased.

I was completely vegan for a couple of years. I went that way to avoid gallbladder surgery - it worked, I had no gallbladder pain on a vegan diet. I Supplemented with B12 and Vitamin D as those are typically low to non-existent in the vegan diet.

But I started to have problems with my teeth chipping - hadn't had that before. I did some calculations and realized that there was no way I was getting anywhere close to the RDA for calcium. So I started supplementing some calcium.

After some gut problems I came to the conclusion that beans weren't working for me. I needed to quit eating legumes for a while which is highly problematic on a vegan diet as they're the major source of protein.

Now I eat a tin of sardines twice/week (and other fish occasionally) which means that technically I'm not vegan any longer. At least the addition of fish did not cause any gallbladder problems.

I can't remember the exact reference here, but I remember a research paper which showed that veganism is associated with an increased risk of cholecystitis.

This is despite the fact that a typical vegan diet is low in fat (which is the typical reason a vegan diet is promoted for gallbladder control). In fact, if I remember correctly, the 'lack' of fat was also the main risk; in that the occasional fact prompted a more violent reaction, thus increasing the risk for an impaction.

I can try and find the article for you if you're interested, though I remember last time I tried to find it it was no easy task trying to sift through the myriad of google results containing vegan blogs recommending vegan diets for cholecystitis... But in any case, if you're going vegan for fear of cholecystitis, be aware it may actually have the reverse outcome!

In my case I was found to have a gallstone - I was having occasional bouts of serious pain in the upper right abdominal region that were becoming more frequent. Ultrasound revealed gallstone.

But in the couple of weeks before I could get the ultrasound I was essentially eating a vegan diet because I wasn't sure what was causing the pain and I wanted to just concentrate on only eating plants to minimize possible triggers. And then when the results came back and the surgeon told me it was time to schedule the surgery, I realized that I hadn't had any pain on my minimal diet. And so decided to give veganism a try for a month or so to see what would happen - and I continued to have no pain.

I think what it comes down to is that some animal fats cause the gallbladder to contract more vigorously - especially red meat, eggs and dairy in my case would trigger pain. I've heard about the issue you're talking about as it's been suggested that since you no longer have vigorous contractions of the gallbladder the gall tends to pool up there. On the other hand I've also heard bitter foods and beets help with this issue.

I always thought being calcium deficient is very difficult to do. But I've never had a vegan diet. I've always had a significant amount of dairy (yogurt/kefir, cheese) in my diet though, which contains enough calcium. (Pesco-vegetarian for a decade+ was the furtherst I got.)

Sardines are great for DMAE---good brain food as well as other benefits (like plenty of calcium); good choice.

Boron deficiency is far more common than calcium deficiency, and it's very important for bone strength, or rather flexibility and cohesion. I highly recommend some Boron supplementation, since it's so easy to be deficient. Just as with all trace minerals, don't over do it (btwn 2mg and 5mg is a good dose for an avg weight adult). 3mg/day is a very common adult dose---that's what contained in 4.5 apples/day; apples are a really good source of boron.

Vit D supplementation is very important these days especially. But mega supplements (of 10k IU or higher) can cause calcium loss. It's better to take smaller doses spread more evenly/frequently than to take a huge doses every two weeks to monthly. 2000 IU per day with a meal should be fine for most avg weight adults; I see no reason to take more. 5000 IU twice a week, spread about evenly, and with a big meal is fine too. I wouldn't get any more coarse than that. Doses much larger than 5000 IU might cause calcium loss, ie. erosion.

> I always thought being calcium deficient is very difficult to do.

The RDA is 1000mg (goes higher as you get older, apparentlty). Broccoli is one of the higher vegan sources at about 100mg in a in a cup. Tofu (depending on how it's made) can be around 400mg in a cup. Beyond that tahini (seseme seeds) is pretty high at 420mg in 100 grams. But I wasn't consistently eating those foods every day. When I'd add up my total for a day I'd often come up with maybe 500mg.

> Most vegans are clueless when it comes to making up deficiencies in typical vegan diets

The same goes for non-vegans.

However non-vegans don't normally need to make up for the deficiencies in typical vegan diets.

yes, and omnivore diets are much much more forgiving as far as avoiding serious deficiencies.

I am not giving up my vegetarian diet due to one study (n = 21) of a potential negative affect (surgical scars). Meat-based standard American diet has negatives as well. Given that the iron and B12 levels were low for the vegans in the study it would be interesting if they supplemented that and check for an improvement.

edit: corrected study participants number

I'm curious if there are good, informative studies about mental health and veganism.

Arguably mental health is more important when considering a choice like veganism.

I found this: https://academic.oup.com/nutritionreviews/advance-article-ab...

also: https://www.psychologytoday.com/us/blog/animals-and-us/20181...

then there is the question: do people with mental health issues tend to gravitate towards veganism or is the diet itself is causing the issues.

I would like to see a study with a large number of participants from diverse backgrounds who are meat eaters and then go vegan and see if that affects their mental health. However a meat eater who is then forced to eat soy products/meat substitutes they dislike may be unhappy for that very reason. Its a difficult test condition to say the least.

You could have seven groups with varying levels of choice: group 1 is forced to be vegan, group 4 is the control group, and group 7 is forced to consume meat. Groups 2-3 would be nudged vegan, 5-6 would be nudged to eat meat.

Measure them all and get happiness and health curves after 5, 10, 15 years.

It would be expensive, but probably a better use of money than a lot of other stuff.

Related: the surgical scars of fasting mouse heal better (various publications report the same results)

The same seems to apply in human, with various individual anecdotal report: https://www.quora.com/Did-long-term-water-fasting-improve-an...

I was told that loading up on carbs helped with recovery and I have a load of stuff downstairs in case i get called in.

I notice the downvotes to my post, but what you was told is demonstrably wrong.

As for how/why it works:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7069085/

"Fasting before or after wound injury accelerates wound healing through the activation of pro-angiogenic SMOC1 and SCG2"

There are various other publications on autophagy (removing old stem cells and making new ones)

For those who are going to say "in mice", the effects of true (water only) fasting has been replicated in humans, in well done trials, in even harsher conditions than surgery: chemotherapy.

Fasting improves various things such as the severity of symptoms during chemo and the efficiency of the treatment:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5921787/

"Short term fasting during chemotherapy is well tolerated and appears to improve quality of life and fatigue during chemotherapy"

It may be counter intuitive, but there's a large body of evidence that fasting promotes healing (check the various reference of this 2018 trial: "Fasting cycles retard growth of tumors and sensitize a range of cancer cell types to chemotherapy" https://pubmed.ncbi.nlm.nih.gov/22323820/ etc

That's not what the senior colorectal doctor at the royal free told me last year.

Your best interest may differ from doctors best interest when treating you (not getting sued, following guidelines, getting paid for not rocking the boat)

So document yourself: medline is free, and with sci-hub, you can get the full versions of anything

EDIT: actually, no, don't document yourself. Ignorance is bliss. Why would I even care? After all, it's your life! And I care even less than your doctor, since we don't even have a contractual relationship (which you have with your doctor by virtue of paying him).

Yeh my amateur research is going to be better than their experience.

> Wound diastasis was more frequent in vegans (p = .008).

To me this is the bad part. Wound diastasis means that your incision opens up again. That is IMO a bigger complication than a scar since it likely requires medical intervention and puts you at risk for infection.

is effect size mentioned in the full text?

Take an iron and B12 supplement. Done.

Most vegans should be supplementing iron and all vegans should be supplementing B12 anyway..

Has anyone managed to actually get hold of the paper?

it would be interesting to see what the potential causality would be for this (vitamins/minerals? hormones from the meat? fats?)

Not a surprise. Collagen is important for healing skin wounds, and vegans get none from their diet. (Collagen is just a protein, so it can be generated by the body, but it's easier for the body to simply take collagen from dietary sources.)

Do you have a source for this? As far as I know, there is no way for the body to uptake and employ collagen directly. It needs to be broken down into smaller peptides, absorbed, and rebuilt, just like any other protein.

Yes, I should have been more specific that collagen gets broken down into collagen peptides. I didn't think I needed to be that specific since it's like the difference between Calorie and calorie (i.e., the distinction is not relevant to the discussion on hand).

We know that the body can use collagen without digesting it first because collagen masks are used to heal burn victims. See, for example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6565829/, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3081477/

Collagen is a protein. It is made up of several "peptides" referred to as "collagen peptides." When it is first digested, collagen is broken down into collagen peptides in the gut. The type of collagen determines the ratios of these peptides. Most, but not all of these collagen peptides get further broken down into amino acids in the gut. (Contrast to whey, which gets entirely broken down into amino acids.) However, a significant portion of collagen peptides can survive digestion, or leave the gut before they are digested. (Up to 10%, depending on the original source of the collagen.) The body can utilize these peptides directly to repair skin, because skin is mostly made of...collagen. The presence of collagen peptides simply lets the body go straight to creating collagen without having to wait while peptides are created from amino acids. (The body will still do that, but it's like starting a construction project with supplies on hand vs having to wait for supplies to arrive or be built.)

Maybe I wasn't specific enough here. When I said "smaller peptides," I should have instead written "free amino acids, dipeptides and tripeptides." The two papers you cited refer to topical application, but your statement in your first comment said that it is easier to get collagen from dietary sources. What I'm asking for is what size of peptide you're calling a "collagen peptide" and a source supporting a mechanism of absorption. Most references I find to "collagen peptides" are for unvetted dietary supplements.

There is not good evidence that peptides larger than 2-3 amino acids can be absorbed into circulation via the gut in more than trace quantities (1). Digested collagen will be rich in certain amino acids (glycine and proline in particular), but calling something as small as a di or tripeptide a "collagen peptide" seems like an oddly arbitrary choice. I am a medical student with significant background in biochemistry, so please don't feel the need to dumb it down for me when you explain.

1. https://www.cambridge.org/core/journals/nutrition-research-r...

Collagen peptides are some of the bioactive peptides referred to in your citation that are known to be capable of passing beyond the gut in more than de minimis quantities... (Though in this context, it's still a small amount of the collagen originally consumed, between 1-10%.)

See https://academic.oup.com/fqs/article/1/1/29/4791729 for a discussion of bioactive peptides.

> However, a significant portion of collagen peptides can survive digestion, or leave the gut before they are digested. (Up to 10%, depending on the original source of the collagen.)

Do you have a source where I can read more about this?

>it's easier for the body to simply take collagen from dietary sources.

Digestion doesn't work like that. Any ingested collagen is broken down to amino acids like all other proteins. Then the amino acids are re-polymerized into collagen.

Digestion doesn't work like that. A great deal of food is not fully broken down by digestion. In fact, many functions of the human body rely on various nutrients/whatever surviving their passage through the gut.

Most, but not all collagen is broken down into collagen peptides in the gut. Most of those collagen peptides are then broken down into amino acids. But not all collagen peptides are broken down, and the peptides that remain can enter the bloodstream where they can be utilized as needed.

(The collagen that doesn't get broken down in the gut tends to come out the other side of the digestive tract intact, because unlike collagen peptides, collagen is too large to enter into the bloodstream and there are no organs after the intestines that can make direct use of collagen.)

That right there would be surprising and disturbing. Collagen that shows up in the diet could arrive with subtle flaws.

Wikipedia: "as of 2011, 30 types of collagen have been identified"

Besides getting the wrong type, it could just be damaged. It also seems like an awfully big molecule to pass from the digestive tract to the blood. If that can pass through, then many poisons would also pass through.

Collagen is bigger than some viruses.

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