Besides agreeing with the aims of vegetarianism for aesthetic and moral reasons, it is my view that a vegetarian manner of living by its purely physical effect on the human temperament would most beneficially influence a lot of mankind.
Source, in full
From a letter to Hermann Huth, Vice-President of the German Vegetarian Federation (27 December 1930). Supposedly published in German magazine Vegetarische Warte, which existed from 1882 to 1935. Einstein Archive 46-756. Quoted in The Ultimate Quotable Einstein by Alice Calaprice (2011), [//books.google.it/books?id=G_iziBAPXtEC&pg=PA453 p. 453]. ISBN 978-0-691-13817-6