Foods to avoid are;
All animal products (that's all meat, fish, eggs and dairy, especially cheeses); microwaved food, processed food, fermented products (yogurt, sauerkraut, soy sauce, pickles, miso etc.); yeast containing products; coffee, chocolate, all alcohol, overly ripe bananas and avocados, all beans, any supplements or protein drinks containing the amino acid " Tyramine". Avoid sugar and salt. All narcotics, antihistamines or analgesics and ephedrine (found in some herbal stimulants, cold remedies and often in Chinese herbal remedies).
What Can I Eat?
Salads, steamed veg, rice, millet, buckwheat, yeast free bread, seeds, nuts, soups, herbs and fruit. On the day of the ritual, it would be better to fast for the whole day. If you can, fast for as many days prior to the ceremony as feasible.
I hope this helps.