Ilex paraguariensis is native to the tropical rainforests of South America and is widely known as yerba mate. Highly valued for its reputed medicinal properties and often brewed into a tea, this evergreen herb increases energy, reduces appetite, burns fat, aids digestion, cleanses the bowels and improves cardiac function, according to Raintree Nutrition's Tropical Plant Database. However, yerba mate also can cause side effects and should be used with caution.
Carcinogenic Properties
An international study, published in the May 2008 issue of Cancer Epidemiology, Biomarkers & Prevention, examined the relationship between yerba mate consumption and the incidence of certain cancers. The study, conducted by medical researchers from the National Cancer Institute and two Brazilian medical centers, concluded that yerba mate leaves, as well as both hot and cold infusions of the herb, contained high levels of carcinogenic polycyclic aromatic hydrocarbons. Carcinogenic PAHs, including benzo(a)pyrene, are strongly linked to cancers of the bladder, esophagus, kidney, larynx, liver, lung and oropharynx. Researchers discovered that PAH levels remained relatively high even when the herb was infused into water, a surprising finding, because PAHs are generally believed to be hydrophobic, or resistant to absorption in water.
Insomnia and Anxiety
Proponents of yerba mate argue that the herb gives users a natural high without the jitters associated with beverages containing high levels of caffeine, such as coffee and cola drinks. Writing in the March 16, 2009, issue of the Los Angeles Times, Elena Conis, a health educator and author, points out that yerba mate's caffeine content averages 80 mg per cup, which is twice the amount found in a cup of black tea but only half of that in a cup of coffee. However, people with a sensitivity to caffeine should limit their consumption of yerba mate, particularly if they already are getting caffeine from other sources. Excessive caffeine consumption can cause irritability, anxiety, restlessness, headaches, nausea and insomnia, suggests MayoClinic.com, which points out that men are generally more sensitive to caffeine than women.
Interactions
The ilex herb in any of its varied forms may interact adversely with other drugs, foods and supplements, according to a fact sheet published by the U.S. Army Center for Health Promotion and Preventive Medicine. For example, yerba mate may potentiate or increase the effects---including the side effects---of a wide range of substances, including asthma medications, bitter orange, disulfiram, some antibiotics such as ciprofloxacin and levofloxacin, cimetidine, clozapine and estrogen. Yerba mate may also increase the effects of guarana, lithium, MAO inhibitors, diabetes medications, including insulin, migraine medications, mixiletine, oral contraceptives and terbinafine. Because of its caffeine content, yerba mate can reduce the effectiveness of medications taken for anxiety or insomnia.
References
- Raintree Nutrition: Tropical Plant Database: Yerba Mate
- High Levels of Carcinogenic Polycyclic Aromatic Hydrocarbons in Mate Drinks
- Los Angeles Times: Yerba Mate Tea: Drink in Moderation
- MayoClinic.com: Nutrition and Healthy Eating: Caffeine: How Much Is Too Much?
- Dietary Supplement Fact Sheet: Yerba Mate (IIex Paraguariensis)
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