No, the fruits grown on cereus jamacaru are not poisonous. In fact, they are sweet and succulent to taste. They are berries that have seeds in the middle therefore, be careful when taking a scrumptious bite!
Besides from the fruit itself, some people do use the stems to cook and eat as a vegetable. On top of that, as a fun fact, the juices of cereus jamacaru can be used for medicinal purposes.
The juice can treat lung and skin diseases and when applied onto the skin, it can help with treating ulcers.