Findings Published in August Issue of Journal of Nutrition
NEW YORK, July 18 /PRNewswire/ -- Drinking four to five cups of tea a day may help maintain a healthy mind and body, according to new research published in a supplement to the August issue of the Journal of Nutrition. One study's results suggest that four to five cups of tea a day may improve attention and focus. This and other studies on tea polyphenols, including research on neurological health, genetic susceptibility to cancer, and insulin sensitivity are included in the Proceedings of the Fourth International Scientific Symposium on Tea and Human Health. The supplement also provides an update on the evidence in support of tea's role in cardiovascular health, and the bioavailability of its beneficial flavonoids.
"This supplement highlights many of the new frontiers being investigated regarding black and green tea's potential public health benefits," said Tea Symposium co-chair, Jeffrey Blumberg, Ph.D., 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. Lenore Arab, Ph.D., Professor of Internal Medicine at the University of California, Los Angeles and Blumberg's partner as Tea Symposium co-chair adds that, "There are tremendous advancements to better understand the mechanisms by which tea may reduce risk for heart disease, certain cancers, type II diabetes, and help maintain neurological function."
Theanine in Tea Increases Attention and Focus
The results of a new human, placebo-controlled, trial published in the Proceedings of the Fourth International Scientific Symposium on Tea and Human Health found that theanine, an amino acid present almost exclusively in the tea plant, including black, green, and oolong varieties, actively alters the attention networks of the brain. "Our results show that after having theanine, individuals had significant improvements in tests for attention, and that activity in cortical regions responsible for attention functions was enhanced," said author John Foxe, Ph.D., Professor of Neuroscience, Biology and Psychology at City College of the City University of New York. "What's more, we have seen that just 20 minutes after consuming theanine, the blood concentrations increase and the brain's alpha waves are impacted. It lasts about three to four hours, which we have speculated may be why people tend to drink a cup of tea every three-to-four hours during the day," added Dr. Foxe.
The new research from Dr. Foxe and his team used electrophysiological measures to monitor brain activity after individuals drank solutions containing a placebo, 50 mg caffeine, an amount of theanine equivalent to five to six cups of tea, or a combined treatment. The subjects were asked to complete a variety of attention-related computerized tasks.
The results from Dr. Foxe's laboratory, the Cognitive Neurophysiology Laboratory at the Nathan S. Kline Institute for Psychiatric Research in Orangeburg, New York, supported by the Lipton Institute of Tea, suggest that the effects of theanine in combination with caffeine are even greater than with either one alone in improving attention. Theanine may work synergistically with caffeine to help induce a more calming, relaxed state, but one that allows the mind to focus and concentrate better at tasks Theanine is known to be absorbed by the small intestine and cross the blood-brain barrier where it affects the brain's neurotransmitters, and increases alpha brain-wave activity. This alpha brain rhythm is known to induce a calmer, yet more alert, state of mind. A cup of brewed tea typically contains between 10 and 20 mg of theanine.
Tea May Protect Aging Brains from Alzheimer's and Parkinson's Diseases
Newly published study by Sylvia Mandel, Ph.D., of the Eve Topf Center for Neurodegenerative Diseases in Israel, show that the active flavonoids in tea may have multiple mechanisms of action on a cellular level on maintaining neurological health. Mandel, who has been studying the effects of tea on brain functions in laboratory and animal models for over a decade, looked at animal models of neurological diseases such as Parkinson's and Alzheimer's. An amount of purified EGCG equal to about two to four cups of green tea per day was provided to animals with induced Parkinsonism as part of their diet to evaluate how their symptoms improved or progressed. They found that when the animals are fed green tea EGCG, the polyphenol appeared to prevent brain cells from dying, and showed improvements in reducing compounds that lead to lesions in the brains of animals with Alzheimer's disease.
"In the past, it was thought that once brain cells were damaged, there was no way to repair them. Not only may the EGCG help prevent brain cells from dying, it appears that the polyphenol may even rescue the neurons, once they have been damaged, to help them repair," says Dr. Mandel.
While numerous studies have concluded that diets rich in fruits and vegetables support the body in fighting neurological decline through antioxidant mechanisms associated with their high flavonoid content, the importance of tea's polyphenolic flavonoids in supporting healthy brain cells appears to go beyond the simple oxygen species scavenging, involving pleiotropic effects on numerous biological pathways to help keep human brain cells from dying and even help repair them when they are subjected to insults that damage the cells' DNA.
Human epidemiological and new animal data from around the world suggests that drinking tea -- especially those rich in flavonoids named catechins -- may help support the brain as we age. Recent publications from earlier this year also contribute to the growing body of research on the potential neuroprotective benefits of tea polyphenols. Tan et al found an inverse association between black tea and Parkinson's disease, based on a 12 year prospective study of over 63,000 men and women, that was due to black tea ingredients separate from its caffeine content. A retrospective study, by Kandinov et al, of nearly 300 patients with Parkinson's disease found that drinking three or more cups of tea per day delayed motor symptoms by 7.7 years. In addition to epidemiological data, results from recent animal studies showed that tea polyphenols may improve memory in Alzheimer's disease (Rezai-Zadeh et al), and be neuroprotective against oxidative stress (Hague et al).
Tea May Alter Cancer Genetics
Results from a tea intervention on the role of green tea on the prevention of cancer provided insights into the cutting-edge field of nutri-genomics, or how gene susceptibility toward chronic diseases can be altered through dietary interventions. Iman Hakim, M.D., Ph.D., M.P.H., Professor and Dean of the Mel and Enid Zuckerman College of Public Health and Professor at the Arizona Cancer Center, University of Arizona, has conducted several human clinical trials over the past decade on the role both green and black tea may play in certain cancers. Her latest human clinical trial suggests that bioactive compounds in tea have a significant effect on genes that impact cancer susceptibility and repair from environmental insults.
"The good news is that we are seeing that green tea is impacting genes that play a role in cancer, but we cannot pinpoint who will be responders versus non-responders at this time," noted Dr. Hakim. "In addition, our recent preliminary data show a beneficial effect of green tea on lipid profile among smokers and former smokers. Since there are no known negative effects of consuming tea, and it may be beneficial, there's no reason not to recommend drinking it." Dr. Hakim recommends at least four cups per day.
Growing Body of Evidence
The Proceedings of the Fourth International Scientific Symposium on Tea and Human Health provides the latest scientific update from key research scientists from top medical institutions in North America, Europe, the Middle East and Asia, based on their clinical, laboratory, and epidemiological studies related to the role of tea in promoting healthfulness and reducing the risk of disease. The ongoing scientific exploration of the health benefits of drinking tea has led to a growing body of research that points to tea as an important contributor to overall health. The Proceedings extends the base of credible, published data supporting the health benefits of tea, encouraging the scientific community to continue exploring this exciting area.
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