Tea is a source of many different types of antioxidants and phytochemicals, which may have wide-ranging health benefits. Black, green, white, and oolong are the most common forms of tea, and all come from different parts of the same plant. Herbal teas come from the flowers or roots of non-tea plants. Most of the research on tea has focused on green tea, because it is the most widely consumed beverage in the world, after water. The major phytochemicals in green tea include gallic acid, and epigallocatechin gallate (EGCG).
Possible benefits of tea
Stroke: Some animal studies have shown that green tea might help prevent stroke.
Cancer: Animal studies and cell studies have shown that extracts of green tea and tea polyphenols might help prevent the development and growth of many forms of cancer by limiting the growth of tumors, and stimulating the destruction of cancer cells.
Weight loss: Some studies have shown that, the green tea catechin epigallocatechin gallate (EGCG) does aid weight-loss efforts. Some evidence shows that the polyphenol content of tea can increase endurance during exercise because of improved fat metabolism (Roberts et al., 2015).
Memory: It does appear hopeful that either green or black tea may help to slow the memory decline that occurs with aging. In one large study, it appears that people who drank either kind of tea at least five times a week had roughly a 30% slower rate of decline on annual Mini-Mental State Examinations than those who did not consume any tea.
Cardiovascular disease: The study of tea in relation to cardiovascular disease remains inconclusive regarding catechin effects on lipid levels, blood pressure, and coronary artery disease. The US Food and Drug Administration has deemed the evidence regarding green tea and heart health as “supportive, but not conclusive.”
Diabetes: Findings on diabetes and tea also are inconclusive, and the evidence seems even less convincing as more studies are completed.
Osteoporosis: A recent meta-analysis which examined the association between tea drinking and the risk of osteoporosis found that tea consumption can increase bone mineral density, but the researchers were unable to draw any conclusions about whether it can prevent fractures due to osteoporosis
Tooth decay: Both black and green teas seem to inhibit bacteria that cause tooth decay.
Parkinson’s disease: A study published in Parkinsonism & Related Disorders found that coffee, black tea, Japanese tea, and Chinese tea all decreased the risk of Parkinson’s disease.
Immune function and autoimmune disease: Research from the Linus Pauling Institute at Oregon State University shows that green tea increases the number of regulatory T cells that play a key role in immune function and suppression of autoimmune disease.
Polyphenols: These are chemicals found in many foods, including tea. They are antioxidants.
Oxygen radical absorbance capacity (ORAC) scores: ORAC is a measure of antioxidants. Tea and many fruits and vegetables are ranked on the ORAC score.
Flavonoids: These polyphenols may have anti-inflammatory and anticarcinogenic properties.
Catechins: These are a form of flavonoids.
EGCG: EGCG is the catechin most present in tea and the catechin most studied for health benefits. EGCG is not fully absorbed by the body and is not “readily available” to the body.
A bottle of a popular tea beverage is not likely to do much for you. The content of actual tea in these drinks is very minor. To obtain any benefits from tea, freshly brewed tea is a much better option.
It is not known whether decaffeinated teas have the same polyphenols or level of polyphenols as traditional brews.
Milk in tea
Originally, it was thought that milk blocked the absorption of catechins. It is now known that it does not, unless you plan to make your tea with milk and then let it sit for 1 hour or longer before drinking it.