Diet is an important factor influencing meditative concentration (dhyāna)

Diet is also an important factor affecting meditative concentration (samādhi). If the body takes in too many nutrients beyond what it needs, the body will react; this then affects the conscious mind, whose reactions become somewhat restless and agitated, the mind not pure, the emotions difficult to control, or requiring forced restraint.

These nutrients include not only meat, fish, tobacco, alcohol, scallions, garlic, and other non-vegetarian and pungent substances, but also vegetarian food. If vegetarian food is nutritionally excessive, it can likewise cause overly intense reactions in the body and emotions, increasing physical and mental burdens, making the mind difficult to purify, and thereby affecting meditative concentration.

Therefore, many people complain that meditative concentration is hard to cultivate; they should then examine their own dietary structure to see whether their nutrition is excessive and superabundant. Nowadays, because material life is rich and colorful, people crave the pleasures of the palate and nutrition, cherishing the physical body and delicious flavors too much, resulting in impurity of body and mind. Greed and anger become difficult to subdue, afflictions are heavy, and of course meditative concentration cannot be accomplished; the contemplative practice (vipaśyanā-caryā) and realization of the Buddha's Dharma become doubly difficult. Thus, although a learner of Buddhism may be broadly learned, fluent in theory, and eloquent in speech, the realization within his mind ultimately never comes to fruition; he merely becomes a disciple who only understands doctrine and a jack-of-all-trades in theory. 

In the Śūraṅgama Sūtra, the World-Honored One required his disciples to abstain from non-vegetarian and pungent foods and to subdue the desiring mind and the angry mind, so that their progress on the path could advance rapidly. But in modern society, material life is too abundant; even vegetarian food likewise affects the purity of body and mind, increasing the desiring mind and the angry mind, so that progress on the path cannot advance rapidly. This should draw the attention of us, the vast body of Buddhist disciples, to adjust our own dietary structure for the benefit of our practice.