How can botulinum toxin in improperly processed canned food cause paralysis?

Botulinum toxin causes paralysis by interfering with the body's nervous system at the biochemical level. When food is improperly processed—specifically when it is not heated to a sufficiently high temperature to kill heat-resistant spores of the bacterium Clostridium botulinum—these spores can germinate in the anaerobic environment of a sealed can. As the bacteria multiply, they secrete botulinum toxin, a highly potent protein poison.12

Once ingested and absorbed into the bloodstream, the toxin travels to the nerve endings in muscles. It acts by blocking the release of acetylcholine, a vital neurotransmitter responsible for signaling muscles to contract. By preventing the release of this chemical messenger, the toxin stops nerve impulses from reaching the muscles. Consequently, the muscles become unable to contract, leading to the condition known as flaccid paralysis. If this paralysis affects the respiratory muscles, it can be fatal, as it prevents the individual from breathing.123