Peppermint (Mentha piperita), spearmint (Mentha spicata) and pennyroyal (Mentha pulegium) are closely-related members of the mint family and have many of the same components. However, unless otherwise noted, "mint" refers to peppermint in the discussion that follows. Mint has traditionally been used with varying degrees of success in the treatment of loss of appetite, irritable bowel syndrome, gallstones, common cold, headache, bronchitis, sinusitis, and pulmonary tuberculosis. While mint has been used in some healing traditions to combat nausea and vomiting, it has not been found effective in treating gastrointestinal side effects related to chemotherapy. Mint contains numerous volatile compounds and other substances that have powerful antioxidant, antibacterial, antiviral, antimicrobial, and antifungal properties. Carotenoids such as beta-carotene and beta-cryptoxanthin, as well as flavonoids such as apigenin and luteolin in mint have been found to have anti-cancer properites. Mint has also been found to reduce blood pressure in rats by means of vascular smooth muscle relaxation. Menthol, a secondary alcohol produced by peppermint, has been shown to have antiseptic, analgesic, and cooling effects.
Cancer-related effects of consuming mint
Several studies have shown mint oil to be protective against carcinogen-induced lung and skin cancers in laboratory mice. Menthol has been shown to enhance the anti-proliferative activity of vitamin D in human prostate cancer cells in the laboratory (however, please note that menthol is toxic when ingested). Various mint extracts have been shown to protect against radiation-induced damage in mouse liver, brain, bone marrow and testicles. It is not clear that these findings should be applied to people undergoing radiation treatment for cancer since mint's radioprotective properties could potentially protect cancer cells from the treatment.
Mint has been found to have hormonal effects at levels of consumption achievable by regularly drinking mint tea. Mint is thought to reduce libido according to some folk medicine traditions. Peppermint and spearmint have been found in several studies to have antiandrogenic effects in rats. For example, one study found that peppermint tea caused total testosterone levels to decrease in male rats and damaged testicular tissue at high doses. Another study found that while mint alone did not exhibit significant estrogenic activity in rats, it enhanced the estrogenic effect of estradiol when they were administered concurrently. One study of hirsute Turkish women found that drinking spearmint tea reduced their hirsutism and resulted a significant decrease in free testosterone and increases in luteinizing hormone, follicle-stimulating hormone and estradiol. We do not mean to overstate these hormonal effects. Women in countries such as Morocco that consume a great deal of mint tea tend to have low rates of breast cancer (which has been attributed to their low initial age of childbearing and non-Western diet, among other factors) and no large populations studies have been performed that assess the association between drinking mint tea and breast cancer. However, based on the very limited evidence available, it is possible that the combination of regular and frequent mint consumption and our estrogenic Western diet could contribute to breast cancer risk.
Men and women who are attempting to start a pregnancy and women who are pregnant or nursing should avoid mint. Mint has been used in various folk medicine traditions to induce abortion and has been shown to have an anti-implantation effect in rats. Regularly drinking mint tea instead of water has also been shown to cause testicular and uterine damage in laboratory rats.
Foods containing mint can promote reflux in some people with gastrointestinal reflux disease (GERD). Various cultivars of mint have been found to cause damage to the liver and brain at high dosages. Essential oil of any type of mint should not be ingested without medical supervision. When taken by mouth, mint oil can interfere with antacids, medicines for high blood pressure, and some other drugs. Mint tea has been shown to interfere with iron absorption and therefore should be limited by those who are anemic or undergoing chemotherapy.
Below are links to recent studies concerning this food. For a more complete list of studies, please click on mint.