“The role of capsaicin in carcinogenic processes is quite controversial. Although some investigators suspect that capsaicin is a carcinogen, co-carcinogen, or tumor promoter, others have reported that it has chemopreventive and chemotherapeutic effects.”

Young-Joon Surh, PhD – in a 2002 editorial for the Journal of the National Cancer Institute about research into capsaicum.

Seeking to unpick the different research findings about chillies suggests the following: 

Capsaicin is the active component of chilli peppers.

Likely to provide pain relief: As Wikipedia reports it is already, ‘currently used in topical ointments, as well as a high-dose dermal patch (trade name Qutenza), to relieve the pain of peripheral neuropathy such as post-herpetic neuralgia caused by shingles. It may be used as a cream for the temporary relief of minor aches and pains of muscles and joints associated with arthritis, simple backache, strains and sprains, often in compounds with other rubefacients. The treatment typically involves the application of a topical anesthetic until the area is numb. Then the capsaicin is applied by a therapist wearing rubber gloves and a face mask. The capsaicin remains on the skin until the patient starts to feel the "heat", at which point it is promptly removed.’

Sixwise reports that Capsaicin is known to inhibit Substance P, a neuropeptide that is the key transmitter of pain to the brain; that substance P can cause swelling of nerve fibers, which may result in headaches and sinus symptoms; and that studies have found that capsaicin both relieves and prevents cluster headaches, migraine headaches and sinus headaches

May help reverse diabetes: Substance P in capsaicin has been shown to reverse diabetes in mice but the effects to insulin secretion seems to be species dependent. In humans, substance P seems to decrease insulin release and cause fluctuations in blood sugar levels.

Mixed results and some concerns as regards stomach cancer: Epidemiological studies in Italy and laboratory studies in Korea (World J Gastroenterol) have suggested that chillies are protective against stomach cancer. However, a population study in Mexico conducted by the Mexican National Institute of Public Health suggested that high intake of peppers (9 – 25 jalapenos per day) was associated with increased stomach cancer rates compared with low intake (no more than 3 jalapenos per day). Population studies in the USA also found that those areas with the highest pepper content in their food (Mexican-American, Cajun and Creole) exhibited higher levels of stomach and liver cancer (Med Hypotheses). Having said this, in 1998 Surh reported that levels of stomach cancer in Mexico, where peppers are regularly consumed, were generally low – and other factors may be at work in the areas studies, including salty, smoked or pickled foods, cigarette smoking, insufficient fruit and vegetables and Helicopter pylori. Other research is also contradictory, for instance with a Yale study in 1994 suggesting chilli powder increased the risk of stomach cancer, whereas a Berkeley study concluded that chillies were protective against stomach cancer.

Given the mixed research findings so far, it would seem sensible not to regularly consume an excessive amount of chillies.

May have an adverse effect on arthritis and the bladder: Arthritis HelpCenters Inc report Harvard Medical School research suggesting that the receptor activated by chemicals in ‘hot’ chilli peppers (which may appear as a flavour enhancer in food) is also responsible for the ongoing, burning pain associated with inflammation, tissue damage and arthritis. Arthritis Health Centres Inc also report that eating ‘hot’ chilli peppers may upset your stomach, irritate the lining of your stomach, irritate your bladder so that you have to urinate more frequently or even make your urination painful.

May protect against prostate cancer – and possibly leukemia and lung cancer: Wikipedia advises that the American Association for Cancer Research reports studies suggesting capsaicin is able to kill prostate cancer cells by causing them to undergo apoptosis. The studies were performed on tumours formed by human prostate cancer cell cultures grown in mouse models, and showed almost 80% of prostate cancer cells in the mice died and that the tumours treated with capsaicin were about one-fifth the size of the untreated tumours. PSA Rising (Prostate Cancer Survivor website) reports similar positive research findings. Wikipedia also reports there have been several clinical studies conducted in Japan and China that showed natural capsaicin directly inhibits the growth of leukemic cells and that a study carried out at the University of Nottingham suggests capsaicin is able to trigger apoptosis in human lung cancer cells as well.

May prevent sinusitis and relieve congestion: Sixwise reports that capsaicin has potent antibacterial properties that fight and prevent chronic sinus infections, or sinusitis; that because it is so hot, it also helps to stimulate secretions that help clear mucus from your nose, thereby relieving nasal congestion; and that this phytochemical may also help relieve sinus-related allergy symptoms.

May protect your heart: Sixwise further reports as follows: That capsaicin may help to protect the heart by reducing cholesterol, triglycerides and platelet aggregation. It may also help the body dissolve fibrin, which is necessary for blood clots to form. Further, cultures around the world that use hot peppers liberally in their meals have significantly lower rates of heart attack and stroke than cultures that do not.

Drug interactions: Capsaicin is indicated as interacting with a number of drugs, including the commonly prescribed high-blood pressure drug Lisinopril, to induce a side-effect cough.


  • As with most natural products and their derivatives (like green tea and garlic for instance) where the nature, quantity and preparation can vary and where, in the case of epidemiological studies, other factors may be at work, further clinical trials are needed.
  • It would appear advisable to avoid excessive consumption of chillies (eg the 9 – 25 jalapenos per day quoted in one Mexican study) and to be wary of chillies if you have arthritis.
  • With these caveats regular moderate consumption of chillies appears likely to have a number of health benefits. 

Published 22/05/2011, Review date August 2014