So many people think that eating meat is healthier, but that’s completely false. Also, the type of person that says that is usually not eating enough fruits and vegetables for optimal health, so that’s obviously just a ploy to justify meat eating. I don’t feel that eating meat is wrong, only that torturing animals (as in factory farming) is wrong, and have no issues with eating shellfish and other animals that don’t have an actual brain, but I digress. There is a lot of misinformation about diets in general, but especially around veganism/vegetarianism. Cats need to eat meat: they are obligate carnivores because they can’t make amino acids, etc on their own. Humans are not, but B12 can only be obtained through the sources such as fermented foods and animal products. However, a supplement would fix that. Plants are also good sources of protein and iron, if you eat the right kinds. But there are plenty of health reasons to avoid animal products that come from the supermarket. I do research on trace concentrations of things like sulfa drugs and endocrine disrupting compounds (EDC) and can tell you that these things do make it through processing and accumulate in the body. There’s also the issue of antibiotic-resistant microbes that are created by the massive use of antibiotics in agriculture, which is necessary due to overcrowding and filth. And it has been shown that a diet high in animal products is linked to an increased risk of a host of diseases, including cancer and heart disease.
The moral of the story is that being a healthy vegan is as difficult as being a healthy meat-eater. You’d have to pay attention to your diet regardless.