ânanda, all beings live if they eat wholesome food and
die if they take poison. In their search for Samàdhi, they
should abstain from eating five kinds of pungent roots (i.e.
garlic, the three kinds of onions and leeks); if eaten cooked,
they are aphrodisiac and if raw, they cause irritability.
Although those who eat them may read the twelve divisions
of the Mahàyàna canon, they drive away seers (çùi) in the ten
directions who abhor the bad odour, and attract hungry
ghosts who lick their lips. They are always surrounded by
ghosts, and their good fortune will fade away day by day to
their own detriment. When these eaters of pungent roots
practise Samàdhi, none of the Bodhisattvas, seers and good
spirits come to protect them, while the mighty king of
demons takes advantage of the occasion to appear as a
Buddha as if to teach them the Dharma, defaming and
breaking the precepts and praising carnality, anger and stupidity;
at their death, they will join his retinue, and at the end
of their time in his realm, they will fall into the unintermittent
hell. ânanda, practisers of Samàdhi should never eat these
five pungent roots.
Full text here. Above excerpt taken from page 230.