I had a vegetarian boss at one time. He was perpetually sick and he finally got a cold that just wouldn’t go away even after he went to his naturopath at read the latest vegan diet book.
I finally got tired of his coughing, sneezing, and whining and told him to go home tonight and eat a steak.
He actually did and came in the next morning and told me he felt much better and had much more energy.
He looked much better and had more color in his face. He had a classic case of anemia.
He seemed much happier after that.
Most “vegetarians” have a dreadful diet consisting of refined grains, fake meat substitutes, and dairy. There are excellent vegan sources of protein (nuts and legumes) but a modest amount of meat is beneficial if the rest of the diet is heavy on plant-derived foods. Look at how primates eat in their natural habitats... breastmilk as infants and then about 8-10% meat (insects, birds, cannibalized young) and the remain 90-92% is vegan (fruit and leaves). They are some of the strongest animals on earth.