In all circumstances they should conduct themselves with moderation; if the meal be only one course this is more pleasing in the sight of God; however, according to their means, they should seek to have this single dish be of good quality.

Bahá’u’lláh, Lights of Guidance, p. 294

Treat disease through diet, by preference.

Bahá’u’lláh, Bahá’u’lláh and the New Era, p. 106

"What will be the food of the future?"

"Fruit and grains. The time will come when meat will no longer be eaten. Medical science is only in its infancy, yet it has shown that our natural diet is that which grows out of the ground. The people will gradually develop up to the condition of this natural food."

‘Abdu’l-Bahá: Ten Days in the Light of 'Akká, p.8- 9

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 the molars. Likewise, God hath given to the four-footed grazing animals such teeth as reap the grass like 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 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 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, Lights of Guidance, p. 294

In regard to the question as to whether people ought to kill animals for food of not, there is no explicit statement in the Bahá’í Sacred Scriptures (as far as I know) in favor or against it. It is certain, however, that if man can live on a purely vegetarian diet and thus avoid killing animals, it would be much preferable. This is, however, a very controversial question and the Bahá’ís are free to express their views on it.

Shoghi Effendi,

In matters of diet, as in medicine, the Universal House of Justice feels that the believers should be aware that a huge body of scientific knowledge has been accumulated as a guide to our habits and practices.

Universal House of Justice, Compilation of Compilations Vol. I, p. 486

As a nursing mother, my wife apologized to ‘Abdu’l-Bahá for what she spoke of as her "great appetite." He however referred to her duties as a mother and the labors which make part of that calling, and to the need therefore for more than usual nourishment. Speaking of appetite and taking food, He said further in part: "Virtue and excellence consist in true faith in God, not in having a small or a large appetite for food, or in similar matters. Jinabi Tahirih (Qurrat-ul-Ayn) had a good appetite. When asked concerning it, she would answer, 'It is recorded in the Holy traditions that one of the recorded attributes of the people of paradise is "partaking of food, continually."' (Whatever may be the outward meanings of this tradition, in its spiritual sense it means that when man is brought into the Paradise of Divine Nearness, through faith, he perennially and perpetually partakes of the food of Divine Bounties and Favors.) "To be brief; when man takes food, it strengthens him in whatever mood or state of mind or condition he may be in at the time of eating. For instance, if a man is full of love, eating food increases his love; on the contrary, when a man is angry and eats food it intensities his anger. Thus it is necessary that man think only of the Love of God. Then if he eats a little more food than may seem usual, it does no harm. But otherwise, that is, if he does not possess the Love of God, to eat little or much food is all the same."

1906 Pilgrim Notes of Ali-Kuli Khan

As for your drink, focus your vision and at the beginning of each day take in your hands, by the might of God and His power, a portion of kundur (frankincense) and qarnaful (cloves) with an equal amount of pure sugar. Drink a cup of water in which the white leaf from China** has been boiled, for drinking it refines the (human) constitution, draws out moisture, and closes the paths of allusions. The one who drinks it is revivified by meeting the people of reality and in it are benefits that cannot be recounted for those who openly bear witness to the path of the Bayan. If you want more than one cup, then drink another, for verily God loves singularity under all conditions. If you like, drink it with milk if you are not cold. That is God's ruling regarding what you should drink an hour after the rising of the sun. Do not drink more than what I have commanded you (to drink) or anything after it except delectable sweets, for they are permitted for you under all conditions. Busy yourself as God has ordained. (The Báb, Sahifa bayn al-haramayn

Scripture between the Two Sanctuaries), Muharram 1261/ mid-January 1845, during his pilgrimage to Mecca and Medina

Eat ye, O people, of the good things which God hath allowed you, and deprive not yourselves from His wondrous bounties. Render thanks and praise unto Him, and be of them that are truly thankful.

Adib Taherzadeh, The Covenant of Bahá’u’lláh, p. 21-22

Some evenings His meal consisted only of a cup of milk and a piece of bread. He described it as a healthy meal, and recalled that Bahá’u’lláh had said that during His sojourn in Sulaymaniyyih His food was just milk most of the time, and sometimes milk and rice cooked together.

H.M. Balyuzi, ‘Abdu’l-Bahá - The Centre of the Covenant, p. 392