Beginners of Vajrayana need not and are, in fact, forbidden to accept the five meats and five nectars. There is an analogy in the Kalacakra Tantra: Some people can cure their illness and prolong life by taking a medicine called Nectar of Brahmā directly, while others are not allowed to drink it but can only carry the nectar in a gawu box around their neck because they will die if they drink the medicine. Similarly, some people may greatly benefit from undertaking the kind of tantric practices that accept the five meats and five nectars, but beginners who try to do the same will incur much harm with no progress to show for it. Therefore, these practices are off limits to them. If and when we reach a state of realization whereby we perceive all phenomena as a dream, with no attachment, we can then adopt the practices to speed up our progress.

- Quote from Gateway to the Vajrayana Path, "The Parable of a Black Snake"