Capsaicin, computer model. Atoms are represented as spheres and are colour-coded: carbon (red), hydrogen (white), oxygen (purple) and nitrogen (green). This chemical gives chilies their heat and causes a burning sensation when ingested. It is a secondary metabolite of the chili plant (Capsicum sp.) and probably evolved to deter herbivores. As of 2006, capsaicin is being investigated as a potential treatment for prostate cancer, as it has been shown to promote prostate tumour cell death in culture. The increased consumption of chilies is not recommended as a preventative measure against prostate cancer because capsaicin has been linked with stomach cancer.