Yerba mate is a traditional South American beverage, an infusion made from the dried leaves and stems of the Ilex paraguariensis plant. It is typically consumed from a hollowed gourd using a metal straw called a bombilla. This herbal drink is popular in countries like Argentina, Uruguay, and Paraguay, where it is consumed daily. This article evaluates the safety of yerba mate during pregnancy, focusing on its composition and the lack of dedicated clinical research.
Understanding Yerba Mate’s Composition
The stimulating effects of yerba mate stem from its content of xanthines, which are naturally occurring alkaloids. The primary xanthines present are caffeine, theobromine, and theophylline, with caffeine being the most significant component. The leaves are harvested, dried, and then steeped in hot water, typically between 70–80°C.
The infusion is also rich in various polyphenols, such as chlorogenic acids and flavonoids, which contribute to its antioxidant capacity. While these compounds may offer health benefits, their interaction with the developing fetus has not been extensively studied. The concentration of these compounds varies widely depending on growing conditions, processing method, and preparation technique.
The Central Issue: Caffeine and Pregnancy Limits
Caffeine is the primary substance of concern in yerba mate because it can cross the placental barrier. The developing fetus lacks the enzymes needed to efficiently metabolize caffeine, causing the stimulant to remain in its system longer than in the mother’s. Exposure to caffeine has been linked to adverse outcomes like low birth weight and an increased risk of premature delivery.
Major health organizations recommend that pregnant individuals limit their daily caffeine intake to a maximum of 200 milligrams (mg) per day. The caffeine content in a single serving of yerba mate varies significantly, ranging from approximately 70 mg to 90 mg per 250 ml cup, though traditional preparations can contain more. Factors like the amount of herb used, water temperature, and steeping time influence the final concentration. For instance, a traditional gourd of chimarrão (a Brazilian preparation) may contain up to 135 mg of caffeine in a 500 ml serving.
Beyond Caffeine: Other Safety Considerations
Secondary concerns relate to yerba mate’s high content of tannins, which are a type of polyphenol. Tannins bind with non-heme iron, potentially inhibiting its absorption in the digestive tract. Iron and folic acid are essential nutrients for healthy fetal development and preventing maternal anemia, making any interference with their absorption a concern during pregnancy.
Another safety consideration is the potential presence of Polycyclic Aromatic Hydrocarbons (PAHs) in the dried leaves. PAHs are contaminants introduced during the traditional smoke-drying process used to cure the leaves. Although studies have found that PAH content is generally low, similar to levels in grilled meats, some research suggests that high exposure to PAHs during pregnancy may be associated with negative fetal outcomes.
Official Guidance and Safe Consumption Practices
Given the lack of definitive clinical trials on yerba mate safety during pregnancy, the general medical guidance is caution and moderation. Experts, including the European Medicines Agency (EMEA), advise restricted consumption due to the high caffeine content and insufficient data. Pregnant individuals should treat yerba mate as a caffeinated beverage and strictly adhere to the established 200 mg daily caffeine limit.
For those who choose to continue consumption, certain preparation methods can help mitigate the risks. Using cooler water, below the traditional 70–80°C, and reducing the steeping time will extract less caffeine and fewer tannins from the leaves. Since PAHs are a concern, selecting brands that are explicitly labeled as “air-dried” or “unsmoked” can help avoid these compounds. Any decision regarding consumption during pregnancy should be made after consulting with a healthcare provider.