Vegans and vegetarians (once a month meat consumption isnt really an omnivore diet) are more likely to be deficient in Zinc, Iron and are more susceptible to osteoporosis due to poor Calcium uptake. Because animal protein does help the body to absorb minerals like Iron, Zinc and the like (it isnt known for sure why and phytates in certain plant foods also hampers mineral uptake) vegetarians and vegans need to overcompensate for those minerals in their food. On the order of about 50% higher than the RDA for omnivores.

Now I am not saying it cant be healthy, it can and there certainly are problems with how the average westerner eats, but I have no confidence in this being done correctly on a mass scale given the data that has come out. eg. 50% of vegans are deficient in B12 as measured by blood test and thats among a population that is likely much more aware of B12 being problematic since it is only naturally found in significant quantities in animal products and almost every meat and dairy substitute on the market is fortified with B12. And that widespread deficiency STILL happens. Vegetarians are less susceptible to B12 deficiency but still generally rely on the dairy industry to obtain that B12 along with Calcium and Zinc. And because B12 is water soluble not fat soluble, it needs to be obtained daily or in higher doses, semidaily. And the effects of B12 deficiency can be delayed months (pernicious anemia) or years (permanent nerve damage with the anemia hidden by excess folate consumption)

People need education and better meat and dairy substitutes that arent as processed to make this work. Right now, most of them have too much salt and saturated fats to be an improvement.