Tea Taste and Quality Affected by Climate Change
HerbalGram cover article addresses impacts of environmental
variation on botanical quality and activity
(AUSTIN, Texas, Sept. 15, 2014) The chemistry,
taste, and health effects of tea can vary with changes in climate, says a new
article published by the nonprofit American Botanical Council (ABC). Recent
research by Selena Ahmed, PhD, on climate change and its effects on the
phytochemical compounds in tea (Camellia sinensis) is part of an
extensive study conducted by Dr. Ahmed in the Yunnan province of southwestern
China and has implications for the future of medicinal botanicals. Dr. Ahmed’s report on her groundbreaking research is the cover article for the current
issue (#103) of HerbalGram, ABC’s peer-reviewed, quarterly scientific
journal.*
Dr. 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,” wrote Dr.
Ahmed. The idea that weather patterns could noticeably change the taste, and
thus the quality, of crops and 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 HerbalGram
Editor-in-Chief Mark Blumenthal. “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.”
Dr. Ahmed writes about 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 studies 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, Dr. Ahmed discovered that tea’s key health compounds (called
catechins) can decrease by almost 50% 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.
Dr. 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, in which she described the cultural significance
and medicinal use of pu-erh tea in Tibet. (Pu-erh is a highly valued and
relatively high-cost variety of Chinese tea.) She also has co-authored The Tea Horse Road: China’s Ancient Trade Road to Tibet (River Books Co. Ltd.; 2011) with photographer Michael Freeman about
the pu-erh trade and the merchants who traveled the fabled ancient trade route
to exchange tea and other goods between China and Tibet. Mary Lou Heiss reviewed the book in issue #94 of HerbalGram.
HerbalGram
is available at some bookstores and natural food stores and is mailed to
members of ABC. Dr. Ahmed’s feature article is posted on the ABC website,
accessible here.
* Ahmed, S. Tea and the taste of climate change:
understanding impacts of environmental variation on botanical quality. HerbalGram.
2014;103:44-51.