The 5th International Scientific Symposium on Tea and Health was held in Washington DC at the US Department of Agriculture on September 19, 2012 – and Michelle Pierce Hamilton was there! The latest research on the role of tea in promoting health was presented by leading nutrition scientists from around the world. In opening remarks by Kathleen Merrigan, PhD, Deputy Secretary of the USDA, it was indicated that a substantial body of research on tea is being formed, and that in the past five years alone, over 5,600 studies have been conducted on tea. Tea remains the second most consumed beverage in the world, next to water, and the health benefits of tea are top of mind for an increasingly educated consumer base.
The research presented indicates compelling evidence that tea, an infusion of the Camellia Sinensis plant, may literally be the world’s healthiest natural beverage when prepared with good quality water. New findings reported tea’s preventative benefits to heart health, including blood pressure, cardiovascular diseases such as heart attack and stroke, as well as reduced risk of cancer, obesity, neurological decline and osteoporosis. Additional new research supported that consumption of tea improves cognition, digestion and may even play a greater role in the microbiota of the body than was previously known. More than ever before, this research supports what those of us who love tea have always felt – that the hundreds of thousands of bioactive components found in tea, once consumed, work synergistically within the cells of the human body; positively supporting the health of virtually every body system from the brain, the skin, heart, the bones and the gastrointestinal tract.
A meta-analysis of several studies found that 3 cups of tea per day resulted in 11% risk reduction of heart attack. Another randomized, double blind placebo controlled study of 19 males found that daily black tea increased blood flow by 7.8-10.3%, decreasing blood pressure with as little as one cup of black tea per day.
A review of epidemiologic studies involving populations of Australia, the U.S. and Europe found that a wide range of tea consumption, from light to heavy tea drinking of green black and oolong teas, supports preventive effects for stroke and benefits stroke outcomes.
A review of published clinical studies indicated that consuming 5 cups of green tea per day contributed to prevention of several types of cancer, including esophageal, lung, breast, prostate and bladder, as well as recurrence of colorectal cancer.
A human clinical trial of postmenopausal women with low bone mass found green tea polyphenols increased bone formation, reduced bone reduction and improved muscle strength at 6 months.
A review of several studies found that green tea consumption can increase energy expenditure and fat oxidation and can therefore have a positive effect on weight loss and weight maintenance.
Metabolism and Microbiota:
Studies on human feeding have confirmed that certain green tea catechins and black tea flavenols are efficiently absorbed into the small intestine and enter the circulatory system where they can benefit throughout the body. Other studies show that some tea polyphenols that are poorly absorbed in the upper GI tract, persist to the colon where they appear to have a beneficial prebiotic or probiotic effect on gut microbiota.
Cognitive Performance and Well-Being:
Collective studies indicate that caffeine and theanine in tea improves attention and cognitive function; specifically, alertness and performance related to accuracy in attention-switching tests. Other studies found tea to positively impact mood and complex problem-solving.
The major classes of tea include white, green, oolong, black and puerh, and although primarily green tea and some black tea have been represented in studies to date, certain polyphenic benefits reported may apply across classes of tea, since all tea contains polyphenic compounds. The catechins responsible for antioxidant effect in unoxidized teas, convert to another class of polyphenol antioxidants, theaflavins and thearubigins, through oxidation.