Lots of confusion I see
Vegetarians are usually fine, they eat some animal products such as milk. They just do not eat meat as opposed to extreme avoidance.
Aliens from a planet orbiting Vega though, usually are nutters, that story about no breast milk, beyond belief. This is a dietary fad.
My personal beliefs are as follows.
We are omnivorous, we have evolved that way, our digestive system is not designed for full vegetable nor carnivorus diet, but we have the acids of a carnivore, and a longer digestive tract, but not as long as a herbivore. Also look at what we can eat compared to a carnivore (look what can kill a dog).
We also must respect our food, not just buy whatever is cheapest, but what is good. This means meat which is of high welfare, no Auschwitz chicken or eggs, outdoor reared pork, decent welfare beef.
Our meat bill is higher than some people because we do not buy the value stuff where only normal welfare is used.
Funny really but British farm animal welfare is among the best in the world.
I never have ready meals, nor mass produced cooking sauces. My wife knows what goes into our food.