[Yerba mate as a safe polyphenolic source during human lactation].

Background: Yerba mate intake is conditioned by assumptions about its benefits and risks for breastfeeding, with a lack of solid evidence. Objective: To evaluate the safety of yerba mate teas during human lactation. Material and methods: Cross-sectional study with 279 adult lactating women from Argentina (years 2013-2020), during the first six months postpartum, without current pregnancy or active pathologies. Social, reproductive, and food data were compiled. Body mass index and percentage of body fat were also established. The adherence to dietary patterns, intake of yerba mate and its phytochemicals were estimated. Milk biochemistry included nutritional, oxidative and tissue markers. Intake means were compared using the Wilcoxon's test depending on the data recorded, while the multiple nonparametric Kernel regression was used to evaluate the effects on body and milk. Results: It was found a wide range of intake, and tube-sipped tea was the main way of consumption. Concerning its constraints, in-cup tea was more used by women without a partner, whereas tube-sipped tea was consumed mainly by employed women, during late postpartum, and with 12 or more years of formal education. Additionally, these teas were an important source of 18 hydroxycinnamic acids and flavonoids. Moreover, yerba mate provided more than 35% of dietary polyphenols. No anthropometric effects or changes in milk nutrients and biomarkers were found. Conclusions: Yerba mate was a safe source of polyphenols, as it did not compromise lactation and maternal nutritional status.