That's why this isn't great. Because this is not "we went vegan to save the oceans". It is "the oceans look like they are already destroyed".
Besides that, I haven't seen any studies that show a vegan or vegetarian diet makes someone healthier.
We can attempt to fix it before ecosystems collapse, if we do it afterwards, the only meat you will be eating will be worms.
That's not evidence that they're healthier for it.
This is an extensive review of many papers from 10 years ago, most data agrees that vegetarian diet is considerably healthier.
More modern literature merely adds that if you go full vegan you need to eat quite some if you want to preserve lean mass.
Most people who are vegan are more likely to be health conscious
Obviously, physically active vegetarians who carefully consider their diet (and eat specifically balanced non-ultraprocessed food) compares well to 100% fast food eating couch potatoes. Also obviously, it's far easier to have a nutritional deficit with vegetarian food.
I have yet to see a study where vegetarianism is just imposed with no other guidance. If you have one, I would love to see it.
There's plenty of Harvard studies too.
There's an abundance of literature that meat causes cancer, cardiovascular diseases, etc, but people aren't different to 50s smokers.
Seriously. It's so obvious that cattle farming is among the most earth destroying activities but people prefer not to see, because it impacts their life. Easier to she'll 50k on a Tesla to feel good.
Also, just to point out, I'm not a vegan, all I'm saying is that meat should be heavily limited, which is what I do myself.
[1] https://med.stanford.edu/news/all-news/2023/11/twin-diet-veg...
Or copy-paste vegetarian culinary traditions. They have worked out most of the dietary kinks.
You must not have looked. Almost all (except for commercially funded) studies prove plant-based diets are much healthier; it's literally the scientific consensus in nutrition.
Otherwise, there are plenty of studies that show that those vegans who neglect to take appropriate supplements have various health problems, e.g. osteoporosis or anemia.
I also have heard of many (and I know personally someone) who were forced to abandon the vegan diet after some time due to health problems, but it is very likely that all such problems have been caused by not taking a complete set of supplements, because most have heard only about B12, and that is not the only substance missing from plants.
Non-vegans have just as many nutritional deficiencies, if not more, like a total lack in fiber. And for every neglectful vegan, there are ten unhealthy animal product-eating individuals with even more debilitating diseases, like diabetes, for example.
Also, DHA/EPA is synthesized in the body; it's not necessary to supplement them, nor any other vitamins you had listed, other than B12 and possibly D3 (depending on your latitude).