Salicylic acid: a link between aspirin, diet and the prevention of colorectal cancer.

Aspirin was introduced into clinical practice more than 100 years ago. This unique drug belongs to a family of compounds called the salicylates, the simplest of which is salicylic acid, the principal metabolite of aspirin. Salicylic acid is responsible for the anti-inflammatory action of aspirin, and may cause the reduced risk of colorectal cancer observed in those who take aspirin. Yet salicylic acid and other salicylates occur naturally in fruits and plants, while diets rich in these are believed to reduce the risk of colorectal cancer. Serum salicylic acid concentrations are greater in vegetarians than non-vegetarians, and there is overlap between concentrations in vegetarians and those taking low-dose aspirin. We propose that the cancer-preventive action of aspirin is due to its principal metabolite, salicylic acid, and that dietary salicylates can have the same effect. It is also possible that natural salicylates contribute to the other recognized benefits of a healthy diet.