>I am irritated by the weak justification though

Pot, kettle.

>Humans evolved the ability to eat meat because it increased their chances of survival in a hostile environment with scarce resources.

It doesn't stop there. Humans have subsequently evolved to thrive on fatty foods. Our understanding of nutritional evolution is incredibly weak. Despite agriculture predominantly giving us access to carbohydrates, human brains are mostly fat-adapted. Many of today's health epidemics are linked to a lack of fat and an excess of carbohydrates. Try finding fatty fruits and veggies: they were incredibly scarce for most the human population until the last 100 years. Several people have noticed significant improvements going predominantly meat. There's more going on here than just the scarcity argument, the scarcity argument is a gross simplification.

>Comfort is the only reason why healthy people eat meat

No. Plenty of people are eating meat to be healthy. People are, in fact, getting frustrated by listening to the advice of the average western diet, listening to dietitians when they get fat, and unable to get in shape despite putting in an insane amount of effort listening to their dietitians putting their hormones out of whack, making them hungry and agitated 24/7, while they keep saying "just keep going". We don't process meat-based products the same way we do plant-based products.

This is not to moralize meat. Rather, this is to indicate people jump on the "meat is bad / lazy / immoral" bandwagon way too quickly, being spoonfed the common narrative without doing an ounce of research and frequently without experience. Just like the average person doesn't eat meat for any other reason than their own comfort, so does the average person stop eating meat because everyone and their mother claims eating plants will save the world. It's becoming a story of "my propaganda is better than yours".

>Many of today's health epidemics are linked to a lack of fat and an excess of carbohydrates.

I'm genuinely curious as to what you're getting at. When you say "excess of carbohydrates", are you referring specifically to processed foods or refined sugars?

>Try finding fatty fruits and veggies: they were incredibly scarce for most the human population until the last 100 years.

Maybe fatty fruits and veggies were scarce for most humans 100+ years ago, but I highly doubt nuts and seeds were. But that doesn't really matter if we're talking about what we can do today. Things like avocados, olives, coconuts, and the above-mentioned large categories of nuts and seeds, are readily available for most people making these sorts of arguments. Plus, if you're vegetarian and not vegan, then you have access to cheese, yogurt, milk, and eggs. It's easy to eat high fat and low carb while avoiding meat, so the argument for eating meat to be healthy on these grounds seems quite weak to me.

> I'm genuinely curious as to what you're getting at. When you say "excess of carbohydrates", are you referring specifically to processed foods or refined sugars?

Long story short: many diseases are insulin linked. Insulin spikes highest by repeatedly eating carbohydrates throughout the day. Fiber decreases those spikes somewhat, but still doesn't compare at all to a fat-based diet or protein-based diet. There are ways to cope with an excess in carbohydrates (heavy exercise is one, fasting is another), but there is no way to cope with a lack of fat. Additionally, mitigation strategies can cause their own problems (many joggers, especially vegetarian and vegan ones, start developing iron deficiencies). The whole "it is just processed sugar" thing is just the tip of the iceberg.

>I highly doubt nuts and seeds were.

Put in perspective: foraging for nuts and seeds is a lot more difficult and intensive than hunting a giant mammal. Plus, the former is a lot more seasonal than the latter.

>But that doesn't really matter if we're talking about what we can do today.

It does. Human evolution and mutation is slow. By looking at what our primary diet was up until recently, we can understand the macronutritional and micronutritional needs of our body and how a vegetarian/vegan diet may or may not influence that.

>Things like avocados, olives, coconuts, and the above-mentioned large categories of nuts and seeds, are readily available for most people making these sorts of arguments. Plus, if you're vegetarian and not vegan, then you have access to cheese, yogurt, milk. It's easy to eat high fat and low carb while avoiding meat, so the argument for eating meat to be healthy on these grounds seems quite weak to me.

The main thing currently under scrutiny is the bioavailability and toxins (for lack of better term) of plant-based foods compared to meat. Turns out a lot of plants don't want to be eaten, and when you can't move, you start developing ways to protect yourself without requiring locomotion. Not only are various of these toxins decreasing bioavailability (zinc is a big one, eating beans with oysters is a terrible way to decrease bioavaialability of zinc), these toxins are actively causing harm and inflammation, whereas a meat-based diet is seen as the "ultimate restriction diet". Avocados, coconuts, olives and nuts stand out here, being more fat heavy, but as most of the population does not have a history with these compared to animal products, it is difficult to say its all good. Beyond that, it is very difficult to get all your minerals and vitamins just on those alone, which isn't the case for meat and seafood, which results in either tapping into the remainder of the veggies and fruit, or tapping into animal products.

Obviously, the argument is more than macros. If macros were all that mattered, you could just stuff your face with whey protein and vegetable oil and call it a day. The argument in favor of meat is a lot more nuanced and without that nuance, will be ruthlessly picked apart by the pro-vegan gang who tend to be a lot more zealous than their carnivorous counterparts (the carnivores have nothing to lose if vegan diets prove to be better, they are already on the moral low). To explain this in its entirety would take far more than a HN comment.

What's concerning is just how much meat-eaters have to play the defense. We don't know that much about vegan and vegetarian diets compared to an ancestry and entire tribes of carnivores. We put forward theoretical models devoid of animal products, using obscure plants to fill in some deficiency, but never test whether it will work on the larger scale. The ecology argument is thrown about as if people don't understand how carbon cycles work. It's humans going vegetarian and vegan which deviates from the status quo, not the other way around. We should be questioning the long term (multi-generational) effects of it as long as we haven't put hoards of people on a vegan or vegetarian diet that didn't include some shady 10 ingredient meat-replacement containing added sugar. We should also be questioning our current understanding of the "cows bad beans good" narrative, and what truly is the cause of the problem (human greed).

Thanks for the response. I won't respond to every point because (1) that would be long and (2) I don't disagree with everything.

> Human evolution and mutation is slow. By looking at what our primary diet was up until recently, we can understand the macronutritional and micronutritional needs of our body and how a vegetarian/vegan diet may or may not influence that.

What was "our" primary diet though? Depending on where a group of humans lived, presumably the diet varied greatly. It seems to me that humans can successfully adapt to a wide variety of foods. I'm sure early humans ate meat, but vegetarianism and pescetarianism date back at least to antiquity. And just because a diet kept us alive doesn't mean it's "good" for us in the modern sense. Say, hypothetically, that a meat-heavy diet increases the risk of early death. That would be irrelevant in the context of natural selection if that age is much older than that of typical reproduction. Our "goals" are different now, too. Does a person sitting at a desk all day require the same nutritional profile as a hunter?

> The main thing currently under scrutiny is the bioavailability and toxins (for lack of better term) of plant-based foods compared to meat.

This is interesting to me and something I've been researching too. It does seem that a lot of the "toxins" can be mitigated by using very old cooking techniques: soaking beans/lentils, cooking vegetables (rather than eating raw), sprouting, fermenting. These techniques can weaken the plants' defense systems, so to speak.

> Avocados, coconuts, olives and nuts stand out here, being more fat heavy, but as most of the population does not have a history with these compared to animal products, it is difficult to say its all good. Beyond that, it is very difficult to get all your minerals and vitamins just on those alone, which isn't the case for meat and seafood, which results in either tapping into the remainder of the veggies and fruit, or tapping into animal products.

To be pedantic: meat doesn't really have a lot of vitamins, right? If you want a complete mix of vitamins and minerals, you would need to eat the kidney, liver, brain, heart, etc, which for whatever reason we don't really do anymore (in the US at least). For the average person (again in the US), this means you will need to step into non-meat sources for e.g. vitamin A or vitamin C. I only bring this up because the topic at hand is specifically about meat, not necessarily eschewing all animal products, so they are presumably allowed in this context.

Sure, you can find subsets of the population whose health depends on incorporating meat in their diet (that's what I meant with "healthy people", although I misworded it; people who need meat in their diet aren't necessarily unhealthy, their health is conditional on consuming meat). I accept that much.

This argument is not very powerful though. For one, it only justifies eating meat for those who have tried to cut meat from their diet and noticed adverse health effects (which should be safe for most people who don't already suffer from some risk factor, like anemia, to try); in my anecdotal experience a tiny minority of the people who make health-based arguments. And secondly, it only justifies the minimal meat consumption necessary to be healthy, and no more.

From a strict evidence-based medicine standpoint we don't have clear evidence for or against vegetarian diets. But if you look at elite athletes whose livelihoods depend on keeping their bodies in peak condition the vast majority consume at least some animal products. So empirically that should tell us something.

There could be a lot of reasons for that. I doubt the reason is that meat is the healthiest option for them; meat contains a lot of saturated fat, which athletes try to avoid too much of. It's more likely that meat is healthy enough for athletes who enjoy eating meat. This wouldn't mean they need meat, and they most certainly don't as there are a lot of successful vegan bodybuilders.

There is no evidence that saturated fat inhibits athletic performance. Vegan bodybuilders are a small fraction of the total, and that's just one sport. What percentage of elite athletes across all sports are vegan?

The overall portion of athletes are vegetarian or vegan is low, but the ones who are can still perform very well. This suggests that the difference is based, at least in part, on preference.

There have also been many athletes who tried vegan diets and found that their performance declined, or they had more difficulty recovering from injuries. So preference is only one factor.