‘Have you ever eaten fresh mint after chilli has burned your mouth? If you have you will have been relieved. Both capsaicin a compound that gives chilli its heat and menthol contained on the outer surface of mint act on the same receptor in the mouth – but in different ways.
The neurologist Professor Anand of the Imperial College London Pain Centre explains why:
The active component of chilli, capsaicin stimulates nerves in the mouth to feel heat and pain via a receptor known as TRPV1. It also makes nerves grow. Capsaicin is an ingenious compound because it deceives the body into thinking it is hot when it is not. Interestingly mint does the opposite. Menthol blocks the receptor and induces a cool sensation in the mouth. South East Asian cooks know this all too well and use minty aromatic herbs in their delicious salads to accompany hot spicy dishes and relishes.’
So does this action of menthol explain why enteric coated peppermint oil (marketed as Apercap, Colpermin or Mintec) is said to help people with IBS? I must admit when it was first released, I was sceptical, and suggested that the most beneficial action of delayed release peppermint oil might be the fact that it disguised the odour of intestinal gas by replacing it with a delicate aroma of mint. Peppermint was originally marketed as an antispasmodic, but a recent study from Adelaide suggests that it’s mode of action might be on pain receptors in the colon. The most recent study on chilli, from Thailand, suggested that it’s major effect was on the sensation of burning, not necessarily crampy pain. So how relevant is the action of chilli and menthol in IBS?