Veganism might be unhealthy in the long term

[Third Person Groove]

This argument goes like this

1. There are little to no 3rd generation vegans.
Since you have to supplement for a vegan diet (b12) and these supplements are per-ity much non existent 50 years ago.

2.there is no way of telling how veganism will affect our health in the long term or through multiple generations.

3.there were no past vegan tribes/ societies that flourished and that are known

...


"Of course we can be obtain all essential nutrients from a vegan diet, also supplementing wouldnt be necessary if we werent so sanitized, maybe I mean im not sure of any study proving we can obtain b12 through the soil and being exposed to other things that seems more like a theory."

There are some long term studies of vegans that seems to show they live longer lives than most others... Although the data seems very limited and too some people it seems to risky because of its (early age) So what is a good reply to this type of comment?

[cornivore]

There are some long term studies you can read about from the National Center for Biotechnology Information. What is our knowledge about nutrtion based on otherwise? People have never known everything about it, yet I haven't read one peer reviewed article that discounts veganism as a healthy choice, while there are ones about the adverse effects of eating dairy, etc.

Conclusions
The use of indexing systems, estimating the overall diet quality based on different aspects of healthful dietary models (be it the US Dietary Guidelines for Americans or the compliance to the Mediterranean Diet) indicated consistently the vegan diet as the most healthy one. —Comparison of Nutritional Quality of the Vegan, Vegetarian, Semi-Vegetarian, Pesco-Vegetarian and Omnivorous Diet

[carnap]

I don't think there is any good reply because there is a real fundamental lack of research on vegan diets. There aren't that many studies on vegan diets and the ones that exist suffer from survivorship bias, that is to say, the studies only end up studying the people that stuck with the diet and the drop-out rates for vegan diets are rather high in western societies. The studies also suffer from selection bias because people choose to adhere to a vegan diet and the people that make such a choose may be differ in some fundamental way than others.

What you really would want to do is study a genetically diverse population of people that is more or less forced into a vegan diet but no such population exists. More realistically you'd design a study that tracked "failures" in vegans overtime (i.e., people giving up the diet) and do surveys and testing to try to see if there was any health reason that contributed to their "failure". You'd also want a longitudinal study that captures people becoming vegan to see if these people are characteristically different than the people that don't.

Personally I suspect that some people are less tolerant of vegan diets than others, we already know of some genetic variants that have an impact on this front and its likely there are many more we haven't discovered. For example mutations in the FADS1 and FADS2 genes impact how well you can convert plant-based fatty acids into the downstream fatty acids your body needs, populations of people that traditionally ate plant heavy diets have a mutation that allows for more efficient conversation.

[brimstoneSalad]

1. There are few to no 500th generation non-cannibals.

2. There's no way of telling how non-cannibalism will affect our health through hundreds of generations

3. There's no species of human that didn't historically practice cannibalism


What's the conclusion here, that we should eat other people?

We're getting a bit out of the domain of science and into philosophy, specifically that of knowledge and what justified true belief is. Stuff like Russel's teapot and unfalsifiability. You can always come up with an ad hoc excuse to stretch your requirements beyond the available knowledge for the sake of extreme skepticism.

There are people like carnap above who are uncharitably (and unreasonably) skeptical beyond what professions believe and recommend (just look at professional dietetic organizations; consensus is that properly planned veganism is fine). This idea of "survivorship bias" is one form of that unreasonable skepticism. There's no reason to jump to such extraordinary speculation.

Most people who quit veganism do it for social reasons, and there's no reason to believe those who have health problems weren't just generally eating very poorly (and there's plenty of anecdotal evidence of that). I'm sure there are rare exceptions of people with weird allergies or digestive conditions, but so far no evidence of such a prevalent condition to explain any meaningful percentage of the failures has ever been found. Kind of one of those "how long do you have to look for bigfoot until you decide he probably doesn't exist?" questions. There will always be true believers, be it in bigfoot or the "survivorship bias of veganism" (like carnap). You can't and won't convince them no matter how much evidence you have because they want to believe.

Look into the fatty acid thing he mentioned, for example; it's completely irrelevant to modern day veganism. Par for the course for those kinds of examples.

[carnap]

There are people like carnap above who are uncharitably (and unreasonably) skeptical beyond what professions believe and recommend (just look at professional dietetic organizations; consensus is that properly planned veganism is fine). This idea of "survivorship bias" is one form of that unreasonable skepticism. There's no reason to jump to such extraordinary speculation.

This comment is really just an ad honimem. And as I've pointed out a number of times, dietetic organizations aren't scientific groups and have no authority on scientific matters. Furthermore the position papers you have in mind aren't even endorsed by the organizations and don't represent the "consensus" of its members as they never voted on it in the first place. And I think the only reason you repeat this appeal to authority is because there is in fact a fundamental lack of research.

The idea that pointing out suvivorship bias in studies is a form of "unreasonable skepticism" is absurd, suvivorship bias can lead to a variety of false conclusions.

And your example with cannibal is just hyperbole, epigenetic changes that impact the 2nd and 3rd have been documented and the possibility of such changes with vegan diets is actually very likely. But whether or not there are any harmful modifications cannot be known until you actually conduct studies. This is not to mention that the issue with vegan diets is that its a new dietary approach and there are no traditional populations you can study.

Also the issue with fatty acid metabolism is by no means "irrelevant" to modern vegans, on the contrary, populations with the gene mutation seem to have higher rates of heart disease and some other diseases due to the high amount of omega-6 in modern diets. Those without the gene don't have the same impact but will instead have a more limited ability to synthesize downstream fatty-acids which may mean that they need fatty acids supplements on a vegan diet. We won't know until there is more research.