Yes, it’s true that peach pits, or peach seeds are poisonous.
When ingested, peach pits release what’s called hydrogen cyanide, a gas that, in enough quantity, will kill you.
Fresh almonds also release hydrogen cyanide gas when digested.
Inadvertent cyanide poisoning happens periodically in countries like Turkey where fresh almonds are regularly eaten, roasting eliminates this danger, by the way.
Other pits to avoid: cherries, plums, apricots, apples, and crabapples. And you thought fruits were good for you.