After water, tea is the most consumed beverage in the world. Not only is it comforting with a pleasant flavor, but it has been known for centuries to confer a variety of health benefits. As research progresses, we are finding more and more reasons to consume tea on a regular basis.
Tea leaves come from the same plant, Camelia sinensis, but differ in the way they are produced. The four major forms of tea are black, oolong, green and white. Black tea is fermented and more processed than the other types. Oolong is semi-fermented as compared to black tea. There are more varieties of flavor from oolong because of the degree of fermentation. Green tea is unfermented and undergoes less processing. White tea is also minimally fermented and processed, but is made from leaves that are picked before they are fully open.
As would be expected, the degree of processing has an influence on the potential health benefits. Beverages made from tea that are more processed, such as instant tea products, would show less benefit.
Herbal teas are not made from tea, but from assorted other plant components. They vary in flavor and potential health benefits based on the ingredients they contain.
Most of the positive research on tea to date has been done on black and green tea. Oolong and white teas have been less studied. Tea contains a category of antioxidants called “polyphenols.” These include a broad number of flavanoids found in many plant-based foods. Tea provides an extremely high percentage of the dietary flavanoids consumed in the United States.
On a daily basis, our bodies are exposed to substances and situations where “free radicals” are produced. Unless countered, these can cause damage to the body – such as damage to blood vessel walls or changes in fats in the blood (like cholesterol) that allow for plaque build-up and resulting atherosclerosis. Many cancers are also related to the production of free radicals. Antioxidants help to counter free radicals and the damage they can cause.
Many Americans are choosing tea for the possible health benefits, many related to the polyphenols they contain. The strongest evidence for the consumption of tea so far, has been related to heart disease and cancer. Studies show an inverse relationship between tea consumption and heart attack risk and death. In the areas of heart disease and stroke, there are substances in tea that may improve blood vessel function. They may also lower levels of total and LDL cholesterol, as well as reduce their oxidation, thus reducing plaque build-up.
When it comes to cancers, those showing the most positive effect from tea are rectal, colon and skin cancers. Other cancers are being studied as well, such as digestive, urinary tract, ovarian and gastric. Much of the benefit comes from the protection against free radical damage. It also appears that the substances in tea may decrease the growth of abnormal cells.
Beyond heart disease and cancer, other promising areas of study involve cognitive health, immune system function, oral health, and weight control. Most of the positive research results on cognitive health has been with green tea. A substance besides the antioxidants in tea has been shown to strengthen the immune system and protect the body against infection (bacteria, viruses and fungi).
When it comes to oral health, tea may act in several ways. It may inhibit plaque formation, reduce cavities, and reduce the risk of oral cancer. Studies are currently investigating the relationship of tea to weight control. Some suggest influences on insulin. Being a non-calorie beverage, tea can also be used to replace higher calorie beverages and contribute to the overall decrease in calorie consumption. Green tea extract has also been used to assist with weight loss, but there is concern for possible toxicity with higher intakes.
What are the amounts of tea needed to confer health benefits? The studies that have been done so far have used a wide range of intakes. Some show benefit from as little as one cup of tea a day. Generally, within reason, the higher the intake, the greater the health benefit.
Obviously, it is not a single food substance or supplement that is responsible for keeping us healthy. However, it appears that tea as part of a healthy diet, can assist with reaching positive health goals. In the research to date, at least one cup a day may prove beneficial. Since there are no negative concerns with moderate tea intake, it might be a good addition if you are not already doing so.
Pamela Stuppy, MS, RD, LD, is a registered, licensed dietitian with nutrition counseling offices in York, Maine, and at Whole Life Health Care in Newington. She is also the nutritionist for Phillips Exeter Academy.
Visit Teas.com.au to start getting the many benefits of tea.
(By Pamela Stuppy, www.seacoastonline.com, June06)