Decades worth of research show that tea may help prevent chronic illnesses. And new research shows tea helps promote weight loss and maintain a healthy weight, improve bone health and activate areas of the brain that bolster attention, problem solving and mood.
While there are differences in the way tea is processed, all tea leaves are packed with flavonoids, health promoting chemicals found in fruits and vegetables, whether the less processed white and green teas or black, the most processed. The less processed tea leaves are, the more health-promoting catechins, a type of antioxidant found in tea, they contain.
The December 2013 issue of the American Journal of Clinical Nutrition featured 12 new articles about the relationship between tea and human health.
Twelve internationally renowned researchers and scientists contributed papers to the AJCN supplement, including experts from USDA, National Institutes of Health, UCLA, University of Glasgow and University of L’Aquila, among others.
They participated in the Fifth International Scientific Symposium on Tea and Human Health, held at USDA in September 2012.
“The scientists who contributed their original research and insights are among the best in the world, and together, this body of research has significantly advanced the science of tea and human health,” said compendium editor Jeffrey Blumberg, PhD, Professor, Friedman School of Nutrition Science and Policy and director, Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston.
“These new peer-reviewed papers add to the previously-published body of evidence that shows that tea can improve human health—both physically and psychologically,” added Blumberg. “Humans have been drinking tea for some 5,000 years, dating back to the Paleolithic period. Modern research is providing the proof that there are real health benefits to gain from enjoying this ancient beverage.”
Highlights of some of the compelling reports published through the AJCN include the following five papers:
Tea Leaf Polyphenols May Promote Weight Loss
Tea polyphenols and the caffeine content in tea increase energy expenditure and fat oxidation, providing benefits for achieving and maintaining an ideal body weight.
Researchers concluded that subjects consuming green tea and caffeine lost an average of 2.9 pounds within 12 weeks while adhering to their regular diet. Population-based studies also show that habitual tea drinkers have lower Body Mass Indexes and waist-to-hip ratios and less body fat than non-tea drinkers.
Tea May Reduce Risk for Some Cancers
Green tea polyphenols may play a role in arresting the progression of certain cancers. For example, in a double-blind, placebo-controlled study, supplementation with 600 mg/d green tea catechins reduced the progression of prostate cancer. The researchers reported that after a year, 9% of men in the green tea supplemented group had progressed to prostate cancer whereas 30% of men in the placebo group had progressed.
Hundreds—if not thousands—of laboratory, epidemiological and human intervention studies have found anti-cancer properties in compounds present in tea. The types of cancer that have shown benefits of tea include cancers of the gastrointestinal tract, lung, prostate, breast, and skin. The proposed mechanisms of action for providing protection against cancer include antioxidant effects, inhibition of growth factor signaling, as well as improving the efficacy of chemotherapy agents.
Tea Catechins are Cardioprotective
Numerous studies suggest tea supports heart health and healthy blood pressure, and appears to be associated with a reduced risk of cardiovascular disease, including stroke and heart attack. New research, published in the AJCN provides further support. Study results published by Claudio Ferri, MD, University L’Aquila, Italy, found that black tea reduced blood pressure, and among hypertensive subjects, it helped counteract the negative effects of a high-fat meal on blood pressure and arterial blood flow.
“Our studies build on previous work to clearly show that drinking as little as one cup of tea per day supports healthy arterial function and blood pressure. These results suggest that on a population scale, drinking tea could help reduce significantly the incidence of stroke, heart attack and other cardiovascular diseases,” concluded Dr. Ferri.
Tea Flavonoids Improve Bone Strength and Quality
Osteoporosis is a major public health concern but new research suggests that polyphenols in green tea may help improve bone quality and strength through many proposed mechanisms. In fact, one study found that tea drinking was associated with a 30% reduced risk in hip fractures among men and women over 50 years old.
Tea Improves Mood, Alertness and Problem Solving
Results from new research published in the AJCN found that drinking tea improved attention and allowed individuals to be more focused on the task at hand. In this placebo-controlled study, subjects who drank tea produced more accurate results during an attention task and also felt more alert than subjects drinking a placebo. These effects were found for 2-3 cups of tea consumed within a time period of up to 90 minutes.