Actually, if you're breastfeeding, there're quite a number of things that you cannot eat.
You can't take alcohol because it will pass into your milk which would be bad for baby because their young livers cannot break it down. Some people overcome this by drinking their DOM immediately after they breastfeed hoping that it will pass out in their urine before the next feed.
Ginger will also cause jaundice in babies. This was told to me by my pediatrician as well as doing some reading up on the internet. So I would say, dont't overdose on ginger if you're breastfeeding.
Broccoli, cauliflower and cabbages are harder to breakdown by babies' tummies too. So eating too much will cause more gas to build up in their tummies which if they dont't pass it out, will become painful and cause them to cry.
Some confinement food also features peanut soup. Though it can be nutritious, peanuts are a high allergen food and might cause allergic reactions in some babies. My baby broke into rashes when I had peanut soup and breastfed him.
There're old folks who also tell me that I cannot drink plain water during confinement and MUST drink longan and red dates tea. I have nothing against that just that if you're breastfeeding that you must keep yourself adequately hydrated or else your milk supply will be affected. Milk is liquid. Your body needs liquid so that it can turn it into liquid milk.
Some people tell me that by drinking more milk, you will produce more milk. Well, your body produce more milk when you drink milk because milk is hydrating your body. Milk is good for you as well as for your baby because of its calcium content and especially so if you're drinking those specially formulated for breastfeeding mums. But some babies, like mine, are lactose intolerant and the lactose that is passed on to the milk will cause allergic reactions like rashes.
Also some confinement food is delicious, but could be damaging to your health, like pig's trotters.
Moral of the story, if you're breastfeeding, whatever you eat, your baby will be receiving it too. So be watchful of what you eat.
As for poisonous or not, to me, it's only poisonous if it's not prepared hygenically.
If you're afraid, you could stick to the common confinement food.
To me, petai doesn't sound poisonous, but if it's fried in chilli, the spiciness could pass on to your milk too. Eat nutritiously. Ensure that you have enough carbo, proteins and fibre and you're on the right track.