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Tea—the most widely consumed beverage in the world next to water—can be found in almost 80 percent of U.S. households. In 2017, people in the U.S. consumed over 84 billion servings of tea—that’s more than 3.8 billion gallons! Tea is versatile: served hot or iced, anytime, anywhere and for any occasion.

Herbal tea is gaining popularity among consumers. It is made by boiling herbs or dissolved plant compounds in water to extract the active herbal ingredients. Herbal tea infusions are believed to fight off heart attacks, cancer and other diseases. However, whether it’s healthier to drink herbal tea hot or cold is unclear.

Claire Maufrais, PhD, and colleagues from the University of Fribourg in Switzerland studied volunteers who drank unsweetened, caffeinated herbal tea (yerba mate) either cold or hot. Yerba mate is a plant native to the South American rainforests. Some research suggests that yerba mate may improve blood sugar and cholesterol levels. It is also sometimes used as a natural remedy for chronic fatigue, headaches and depression.

The researchers monitored the volunteers’ heart rate, blood flow, blood pressure, amount of oxygen their bodies used, and how much fat was broken down to release energy (fat oxidation) for 90 minutes after each drink was consumed. They found that drinking the tea at cold temperatures boosted a metabolic process in which the body burns calories to produce heat. Compared to hot tea, cold tea also increased fat oxidation without causing stress to the volunteers’ cardiovascular systems. Maufrais’ next goal is to evaluate if cold herbal tea could be effective for weight control.

Read the full study about herbal tea by the University of Fribourg’s research team in Frontiers in Physiology.

Nathalie Fuentes is a PhD candidate in the biomedical sciences program at Penn State College of Medicine. Her studies in Dr. Patricia Silveyra’s lab include the development of sex-specific therapies to treat lung diseases, sex differences in asthma-related lung inflammation triggered by ground-level ozone and the role of male and female sex hormones in lung disease. Nathalie is originally from Caguas, Puerto Rico.

Nathalie served as a meeting blogger for Experimental Biology 2018.