Buddhist monks observe a strict code of conduct (vinaya) in order to discipline the body and mind. Food is regarded simply as a means of keeping the body alive so that the spiritual path may be followed. Food is not taken in order to beautify the body or because it has a pleasant taste.
A meal in the evening may cause drowsiness and make the practice of meditation difficult. Monks discipline themselves to be satisfied with very few material things, including food. Also by eating only one meal a day, they reduce the burden on the lay community which supports them. An exception to the rule of not eating after noon is made during an illness.
According to the vinaya rules, a monk should only eat what is offered to him and he should accept any item without showing pleasure or displeasure.The offering (dana) of food to the monks has been the tradition from the days of the Buddha.
Any type of food (not containing alcohol), which is normally taken by lay people, is suitable for offering to monks, bearing in mind that many monks prefer to be vegetarian. The monks are prohibited to eat meat of animals specially killed for the offering, if they are aware of it.
http://www.londonbuddhistvihara.org/qa/ ... practices6