“Some persons in Europe carry their notions about cruelty to animals so far as not to allow themselves to eat animal food. Many very intelligent men have, at different times of their lives, abstained wholly from flesh; and this too with very considerable advantage to their health. … The most attentive research which I have been able to make into the health of all these persons induces me to believe that vegetable food is the natural diet of man; I tried it once with very considerable advantage: my strength became greater, my intellect clearer, my power of continued exertion protracted, and my spirits much higher than they were when I lived on a mixed diet. I am inclined to think that the inconvenience which some persons experience from vegetable food is only temporary; a few repeated trials would soon render it not only safe but agreeable, and a disgust to the taste of flesh, under any disguise, would be the result of the experiment. The Carmelites and other religious orders, who subsist only on the productions of the vegetable world, live to a greater age than those who feed on meat, and in general herbivorous persons are milder in their dispositions than other people. The same quantity of ground has been proved to be capable of sustaining a larger and stronger population on a vegetable than on a meat diet; and experience has shewn that the juices of the body are more pure and the viscera much more free from disease in those who live in this simple way. All these facts, taken collectively, point to a period, in the progress of civilization, when men will cease to slay their fellow mortals in the animal world for food, and will tend thereby to realize the fictions of antiquity and the Sybilline oracles respecting the millennium or golden age.”

Philozoia; or Moral Reflections on the Actual Condition of the Animal Kingdom, and on the Means of Improving the same, Brussels: Deltombe and W. Todd, 1839, pp. 42 https://books.google.it/books?id=hdVq93Ypgu0C&pg=PA42-43.