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Climate Change Alters Tea Quality

<p>New research on climate change and phytochemical compounds in tea shows the chemistry, taste and health effects of tea can vary with changes in climate.</p>

AUSTIN, Texas—New research on climate change and phytochemical compounds in tea shows the chemistry, taste and health effects of tea can vary with changes in climate. (HerbalGram. 2014. 103:44-51.)

Selena Ahmed, Ph.D., conducted an extensive study in the Yunnan province of southwestern China to discover more about the future of medicinal botanicals. Her report appeared in the American Botanical Council (ABC)’s peer-reviewed journal Herbalgram.

Ahmed has worked in the Yunnan province for eight years, studying how weather pattern variations impact the naturally occurring phytochemicals and beneficial health properties of tea. Her forthcoming research will investigate how the effects of climate change could alter the benefits of other medicinal plants.

Chinese tea farmers have a finely attuned sense of how differing weather patterns affect the taste and quality of their crop: In the dry seasons, the tea leaves are more potent; in the wetter monsoon seasons, the leaves have a gentler taste and aroma.

“The majority of tea farmers I have interviewed state that climate patterns have shifted noticeably over their lifetimes; such observed changes include warmer temperatures, greater unpredictability of weather such as increased variation of rains, and changing phenology of plants (i.e., the effect of weather patterns on plant growth cycles, including flowering and fruiting seasons, etc.), including earlier bud burst," Ahmed said in the report.

The idea that weather patterns could noticeably change the taste and quality of crops, as well as influence the livelihoods of the farmers, prompted her to analyze samples of tea from successive growing seasons to ascertain what differences are present on a chemical level.

“Tea is the world’s most widely consumed beverage, after water," said Mark Blumenthal, HerbalGram editor-in-chief. “A vast body of scientific and medical research in the past several decades shows many strong correlations between tea, particularly green tea, and abundant health benefits. Dr. Ahmed’s research has compelling implications not only for tea, but for other food and medicinal plant crops, for which changes in climate can cause alterations in taste, and, accordingly, the plants’ nutritional and medicinal values."

Ahmed wrote that her tea research and connects the phenomenon in China with tea growers in other regions, including Sri Lanka, Hawaii, and Japan. In collaboration with researchers from Tufts University and the University of Florida, she studied the chemistry behind the shift in functional quality and secondary metabolites in the tea plant. Plants produce secondary metabolites as a defense mechanism in response to environmental stressors, and a high concentration of these metabolites often correlates to higher nutritional and therapeutic benefits for the consumer.

Through laboratory studies of extracts made from tea samples collected from the Chinese farms, Ahmed discovered tea’s key health compounds (called catechins) can decrease by almost 50 percent when the leaves are harvested after the monsoon season as compared with leaves harvested after a drought. This is consistent with anecdotal observations concerning changes in tea flavor noted by the farmers she interviewed; the differences in flavor correspond with her analyses of the plants’ overall chemistry, including the catechins.

Ahmed is an assistant professor of Sustainable Food Systems at Montana State University. She previously wrote another cover article for HerbalGram, “Pu-erh Tea and the Southwest Silk Road: An Ancient Quest for Well-being," featured in issue 90 in 2011, where she described the cultural significance and medicinal use of pu-erh tea in Tibet.

Previous research shows green tea may provide benefits to eye health.

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