From The Chandogya Upanishad

"From purity of food follows the
purity of the internal organ"
-Chandogya Upanishad, Vii.26.2
[Note:Mind is the internal organ]

"Mind is surely made of food, vital force
is made of water,and speech is made of fire"-
-Chandogya Upanishad VI.6.5

"Of curd when it is churned, that which is its
subtle part rises upward. That becomes
clarified butter. In this very way, of food when
it is eaten, that which is the subtle part, that
rises upward, and that becomes mind"
-Chandogya Upanishad, Vi.6.1 & 2

‘When nourishment is pure, reflection and higher understanding are pure, memory becomes strong. When memory becomes strong, there is release
from all the knots of the heart.’
-Chandogya Upanishad,  I.  vii. 

From The Bhagavad Gita

The food also which is dear to each is threefold.
– Gita,17.7

That food which increases life, purity, strength, health,
joy and cheerfulness, which are savoury and oleaginous, substantial and agreeable, are dear to the Sattwic (pure) people.
–  Gita, 17. 8

The foods that are bitter, sour, saline, excessively hot, pungent, dry and burning are liked by the Rajasic and are productive of pain, grief and disease. - Gita 17. 9

That which is stale, tasteless, putrid, rotten and impure
refuse, is the food liked by the Tamasic. – Gita, 17.10

From Sattwa (purity) arises wisdom or knowledge; from Rajas (passion) arises greed; and from Tamas (inertia) arises heedlessness, delusion and ignorance.
- Gita, 14.17

From Tattiriya Upanishad

Out of Brahman, who is the Self, came akasha (space); from akasha, air; from air, fire; from fire, water; from water, earth; from earth, vegetation; out of vegetation, food; out of food the body of man. The body of man, composed of the essence of food, is the physical sheath of the Self.
-Taittiriya Upanishad, II.i.3

Let him (the knower of Brahman) never condemn (deprecate) food; that is the vow.

The prana (vital breath or vital energy) is, verily food; the body is the eater of food; for the vital force is lodged in the body. The body rests on the prana; the prana rests on the body. Thus food rests on food.

He who knows this resting of food on food is established; he becomes a possessor of food. He becomes great in offspring and cattle (prosperity) and in spiritual radiance (luster of holiness) and great in fame.

-Taittiriya Upanishad, III.vii.1

[Note: Comments by Sri Sankaracharya, translated by Swami Gambhirananda: Since Brahman is realised through the portal of food, one should not deprecate food. The inculcation of the vow is meant for the praise of food; and food is worthy of praise, since it is an aid to the realisation of Brahman (The Supreme Reality).]
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Of all the restrictive rules, that relating to the taking of sattwic food in moderate quantities is best; by observing this rule, the sattwic quality of mind will increase, and that will be helpful to Self-inquiry.
- Sri Ramana Maharshi
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From The Mahabharata

A Brahmin (priest) should abstain from meat.
The Mahabharata
Anusasana Parva, Section XCIII

The sin of eating meat is ascribed to three causes. That sin may attach to the mind, to words, and to acts. It is for this reason that men of wisdom who are endued with penances refrain from eating meat. -The Mahabharata, Anusasana Parva, Section CXIV

Well-dressed, cooked with salt or without salt, meat, in whatever form one may take it, gradually attracts the mind and enslaves it.
The Mahabharata, Anusasana Parva, Section CXIV

[Note: By eating meat, one feels the desire for meat increasing. A taste or predilection for meat is thus created. Hence the best course is total abstinence from meat.]