Hmm... I'm not sure that follows. The ACE-inhibitor drugs like lisinopril (and several others ending in -pril) are front-line drugs for treating high blood pressure. I take lisinopril myself, as do other friends and family members.

The ACE-inhibitors are modifications of a substance found in the venom of Bothrops jararaca, a South American pit viper. Scientists observed that when a prey animal is bitten by one of these snakes it experiences a sudden and profound drop in blood pressure (ideally to zero, from the snake's point of view).

You could argue that allowing yourself to be bitten by one of these snakes would somehow be more "natural" than taking a pill, but myself, I'm going to stick with the pill. :-)

While perhaps not as dramatic, vitamin A is also quite toxic in large amounts. Some of the early polar explorers came to grief from eating sled dog livers or other animal livers.