My Answer: Who cares?
I know, I know. It is a popular belief or canard (depending upon your position) found on both sides of the vegetarian debate. And the amount of energy being used to discredit the story is massive.
What is true? That’s difficult to suss out. What is known is that he did at least play with the idea of vegetarianism for a short period of time. A Slate article from 2004 that interviews noted vegetarian and author Rynn Berry, states:
While (Berry’s) book doesn’t quote any primary sources, the secondary sources Berry uses—newspaper articles, memoirs, other historical texts—seem reputable. The generally accepted idea about Hitler’s nutritional regime seems to be that he at least tried to be a vegetarian. Sometime in the early 1930s, after the mysterious death of his niece and confidant, Geli, Hitler swore off meat. Some say seeing her corpse turned his stomach away from flesh. Others say his doctors put the despot on a vegetable-only diet to relieve excessive flatulence and sweating.
After that, there’s little to any reputable evidence to support that he either stuck with the plan, or let it go.
But again? Why does it matter? The myth exists clearly to illustrate that being a vegetarian doesn’t allow one to stand on a higher moral ground. This is a true statement whether Hitler was a vegetarian or not.
And what if he was a vegetarian until the end? Does it diminish a movement’s compassionate stance in any way? Not at all. Hitler was a dog lover too. Does that compromise the work of the ASPCA?
What this is is the worst aspects of Reductio ad Hitlerum in action when people talk about vegetarianism. Hitler’s place in history is well known, and his personal nutritional choices bare little insight to anyone else’s character.
For the record? I don’t think he was. But it doesn’t change my perspective on meat eaters. After all, Abraham Lincoln, Winston Churchill, and Martin Luther King all were omnivores as well.