I have read of people using raw nuts and seeds to break a fast within a couple of days of a 40 day fast with only positive results. This is with severe illness that particularly wanted a LOT of repair of vital organs damaged by that illness- not a normal case at all. I personally prefer to wait nearly half the time I fasted before adding nuts and seeds in small quantities and make sure I fletcherise or chew them thoroughly before swallowing.
I can't comment on the flesh as my answer would be biased of course.