With so many claims about the health benefits of tea, it’s difficult to separate the facts from the fannings and dust.
Nutrition scientists have sifted through the tea leaves for us and presented their findings at the 5th International Scientific Symposium on Tea and Human Health held at the U.S. Department of Agriculture in Washington DC in September.
Jeffrey Blumberg, Chairman of the symposium and Director of the Antioxidants Research Laboratory at Tufts University in Boston, listed “a multiplicity of potential benefits” — relating to arthritis, cancer, diabetes, high blood cholesterol, memory function, osteoporosis, and weight management — that can come from drinking tea.
Even the process of brewing and enjoying tea may turn out to improve health.
According to Johanna Dwyer, Senior Nutrition Scientist at Tufts and at the NIH Office of Dietary Supplements, drinking tea has had “inconsistent but generally positive associations with some health benefits.” She cautioned that “we need to find and fill in gaps in evidence” to make a convincing case.
Much research has focused on flavonoids, compounds found in tea, as well as in other plant foods.
One big plus regarding tea consumption as a healthful option is that it is associated with few safety concerns. The drawback, Dwyer said, is that “tea is complicated.” Many variables affect flavonoid content, including the type of tea, whether or not the tea is oxidized, whether it is blended and how it is brewed.
Dwyer called for more clinical studies but, with government money limited, she urged private-sector assistance. “Some industry-funded studies on cocoa did very good research [on flavonoids]. I encourage the Tea Council to invest.”
She also encouraged the researchers to do a better job of sending consumers “specific, actionable messages about the benefits of consuming flavonoids,” based on the evidence that has been gleaned so far.
Tea for Heart Health
Dr. Claudio Ferri reads a lot of good news in black tea leaves.
Black tea may help counter the adverse effects of high-fat foods on blood vessels, potentially reducing the risk of atherosclerosis, or hardening of the arteries, the most common cause of death in the United States.
Ferri, Director of the Division of Internal Medicine at the University of L’Aquila in Italy, conducted a small study in which subjects were given a cup of black tea before eating a high-fat meal. The tea drinkers did not experience the usual increase in blood pressure that normally is associated with a fatty meal.
“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,” said Ferri. The results suggest that “on a population scale, drinking tea could help reduce significantly the incidence of stroke, heart attack and other cardiovascular diseases.”
Lenore Arab, professor at the UCLA School of Medicine, specializes in examining the cardiovascular benefits tea may provide. She’s looked at studies that have included a wide range of tea consumption, from light tea drinking to heavy tea drinking populations and included populations that favor black, green or oolong teas.
Among the studies is one that found that three cups of tea per day is associated with an 11 percent reduction in risk of myocardial infarction or heart attack.
Arab also said there is evidence, so far only in animal studies, that tea may reduce stroke-related brain damage.
Suzanne Einöther, with Unilever R&D, Vlaardingen, the Netherlands, reported on a study designed to measure attention, task performance and alertness. Subjects drinking tea were more accurate in performing the assigned task and also felt more alert than subjects who were given a placebo.
This work supports earlier studies on the mental benefits of tea. In addition, two other studies have shown benefits for tiredness and self-reported work performance, as well as mood and creative problem solving.
Green Tea and Weight Control
Obesity is another serious health threat that many be eased by tea drinking. The good news is that not only does tea have no calories, but it may help burn calories.
Drinking green tea, which is high in catechins, can help maintain body weight or promote weight loss, according to Rick Hursel, a researcher at Maastricht University in the Netherlands. Catechins, in combination with caffeine, can increase energy expenditure by 4 to 5 percent and fat oxidation by 10 to 16 percent, Hursel said.
The conclusion, he said, is that “green tea contributes to body weight regulation.”
The Cancer Question
Whether drinking tea plays a role in preventing cancer is not clear. So far there are plenty of laboratory studies that indicate that it can help prevent cancer in animals, according to Joshua D. Lambert, assistant professor of Food Science at Pennsylvania State University. Unfortunately, the benefits of tea for cancer prevention in humans “remains to be conclusively demonstrated.”
A review of clinical studies does suggest that drinking five cups of green tea a day can help prevent several types of cancer and may protect against the recurrence of colorectal cancer.
Continued research is critical because “there are so many people who drink tea, that whatever we find is important from sheer scale,” Lambert said.
Tea for Healthy Bones
Green tea also seems to promote bone health and help prevent osteoporosis, a degenerative bone disease particularly common in post-menopausal women. Research shows that the bioactive components of green tea increase bone formation and reduce bone resorption.
“Osteoporosis is a non-curable disease, so prevention is key,” said Chwan-Li (Leslie) Shen, associate professor of Pathology at the Texas Tech University Health Sciences Center.
The research presented at the symposium confirms that tea drinkers have the right idea. While taking catechin supplements may offer some type of benefit, supplements are no substitute for the beverage.
The many bioactive compounds in tea appear to work together “to impact virtually every cell in the body to help improve health outcomes, which is why the consensus emerging from this symposium is that drinking at least a cup of green, black, white or oolong tea a day can contribute significantly to the promotion of public health,” Blumberg said.
