What should be man's natural food diet?

Words from the Master

"All the teeth of man are made for eating fruit, cereals and vegetables..."

1. Regarding the eating of animal flesh and abstinence therefrom, know thou of a certainty that, in the beginning of creation, God determined the food of every living being, and to eat contrary to that determination is not approved. For instance, beasts of prey, such as the wolf, lion and leopard, are endowed with ferocious, tearing instruments, such as hooked talons and claws. From this it is evident that the food of such beasts is meat. If they were to attempt to graze, their teeth would not cut the grass, neither could they chew the cud, for they do not have molars. Likewise, God hath given to the four-footed grazing animals such teeth as reap the grass like a sickle, and from this we understand that the food of these species of animal is vegetable. They cannot chase and hunt down other animals. The falcon hath a hooked beak and sharp talons; the hooked beak preventeth him from grazing, therefore his food also is meat.
   
        But now coming to man, we see he hath neither hooked teeth nor sharp nails or claws, nor teeth like iron sickles. From this it becometh evident and manifest that the food of man is cereals and fruit. Some of the teeth of man are like millstones to grind the grain, and some are sharp to cut the fruit. Therefore he is not in need of meat, nor is he obliged to eat it. Even without eating meat he would live with the utmost vigour and energy. For example, the community of the Brahmins in India do not eat meat; notwithstanding this they are not inferior to other nations in strength, power, vigour, outward senses or intellectual virtues. Truly, the killing of animals and the eating of their meat is somewhat contrary to pity and compassion, and if one can content oneself with cereals, fruit, oil and nuts, such as pistachios, almonds and so on, it would undoubtedly be better and more pleasing.
         ('Abdu'l-Bahá, from a Tablet - translated from the Persian)
   
   
2. Thou hast written regarding the four canine teeth in man, saying that these teeth, two in the upper jaw and two in the lower, are for the purpose of eating meat. Know thou that these four teeth are not created for meat-eating, although one can eat meat with them. All the teeth of man are made for eating fruit, cereals and vegetables. These four teeth, however, are designed for breaking hard shells, such as those of almonds. But eating meat is not forbidden or unlawful, nay, the point is this, that it is possible for man to live without eating meat and still be strong. Meat is nourishing and containeth the elements of herbs, seeds and fruits; therefore sometimes it is essential for the sick and for the rehabilitation of health. There is no objection in the Law of God to the eating of meat if it is required. So if thy constitution is rather weak and thou findest meat useful, thou mayest eat it.
         ('Abdu'l-Bahá, from a Tablet - translated from the Persian)

Who is Abdu'l-Baha?