Quote
Cottonseed contains about 22% protein, and the cotton already produced worldwide has enough protein to meet the requirements of 500 million people. But it also contains the toxin gossypol, making it poisonous to animals, including humans.
In people, gossypol lowers blood potassium to dangerous levels, resulting in fatigue and even paralysis. A surprising side effect is that gossypol is an effective male contraceptive, but research on this aspect was abandoned in the late 1990s. Attempts to eliminate gossypol from cotton plants in the 1960s and 1970s failed: insects that had previously been kept at bay by the toxin happily ate the modified plant.