High doses of caffeine present in yerba mate might lead to side-effects such as nervousness, heart palpitations and insomnia.1
Yerba mate should not be drunk by people who are supposed to refrain from drinking coffee or tea.
There is no evidence of any negative effects of yerba mate on the pregnancy or the development of the foetus. However, as it has a high amount of caffeine, it is advisable to limit the intake of yerba mate during pregnancy. The Food Standards Agency recommends a daily limit of 200 mg of yerba mate for pregnant women.2
Tests on 5304 new mothers were carried out in Pelotas in south Brazil between 1st January and 31 December 1993. There were 5189 single baby births in the group. The mothers were interviewed; the length of the pregnancy recorded and the newly born babies were measured. 68% of mothers confirmed that they drank yerba mate at least once a week throughout the pregnancy. The test results showed no correlation between the intake of yerba mate and the incidence of premature births or abnormally low birth weight among babies. In the Pelotas area people drink daily approximately 1.8 litres of mate containing c.17 mg caffeine per 100 ml of mate, which is the equivalent of drinking 300 mg of caffeine per day.3
Women who are breastfeeding should limit their drinking of yerba mate to a maximum of 2 cup a day. Caffeine passes into a mother’s milk and might cause hyperactivity in her child and difficulties with falling asleep.4 For this reason the amount and strength of all drinks containing caffeine, including tea and coffee, should be limited.