Hey there, time traveller!
This article was published 2/11/2012 (1496 days ago), so information in it may no longer be current.
A tea timeout is my favourite way to de-stress a day. It feels so civilized to relax with a warm cup of jasmine-scented green tea or perhaps the traditional English treat, black tea with milk -- "white," as they say. Still, with all the myths we hear about nutrition, I've always wondered: Is tea as healthful as many people believe?
Although tea has been enjoyed around the world for some 5,000 years, it wasn't until relatively recently that scientists started searching for the facts.
From the 1970s to the 1990s, epidemiological studies -- the kind following large populations' eating and disease patterns -- found tea drinking might be associated with better health. But no clear cause-and-effect relationship between health and tea was established.
"More careful clinical and laboratory studies are needed," said Johanna Dwyer, a professor at Tufts Medical School in Boston, at the fifth International Scientific Symposium on Tea and Human Health held in September at the U.S. Agriculture Department in Washington, D.C.
But recent studies have been promising. What did they find? Just about every cell in the body could potentially benefit from tea -- with virtually no downsides.
All true tea (white, green, oolong and black, as opposed to herbal varieties) comes from one plant: Camellia sinensis. The differences are in how they are processed, with white and green being the least processed, oolong in the middle and black the most processed. The processing changes the nutritional profile and some of the health effects. But no matter the process, all tea leaves are dense with flavonoids, health-promoting chemicals found in fruits, vegetables, whole grains and most plants.
"About one-third of the weight of a tea leaf is flavonoids, which is high, especially when you consider there are virtually no calories," said Jeffrey Blumberg, professor of nutrition science and policy at Tufts University and chairman of the tea symposium. "A serving of tea is like adding a serving of fruits or vegetables to your diet."
But can tea produce more health benefits than fruits or vegetables? Flavonoid research results are exciting but mixed, and there is still a lot to learn.
There are "small but possibly significant health effects, but study quality needs to improve. The variety, geography, processing and brewing of tea must be considered since it will dramatically change flavonoid content and possibly associated health benefits," Dwyer said, adding, "Tea is not a drug, and to expect a drug-like effect is unrealistic."
So, while not a miracle cure-all, there is some exciting news about tea:
It helps your heart by keeping blood vessels unclogged and flexible. Blood pressure and stroke risk were reduced in epidemiological and clinical studies (even with sugar added).
In a double-blind, randomized study in which hypertensive men drank one cup of black tea daily, both systolic and diastolic blood pressure were reduced. The blood-pressure-lowering effect was maintained even after a large intake of fatty, sugary food, which usually constricts blood vessels, showing "cardiovascular protection can be achieved even without much sacrifice and with normal intakes," said Claudio Ferri, a professor at Italy's University of L'Aquila School of Internal Medicine and co-author of the study.
Healthier blood vessels create better blood flow, which means all of your organs, including the brain, are receiving more blood, oxygen and nutrients, enhancing your body's ability to fight disease. So, healthier blood vessel linings might be one reason why tea consumption seems associated with so many benefits.
It improves bone health. After drinking four to six cups of green tea daily for six months, post-menopausal women with low bone mass (osteopenia) achieved an improvement in certain short-term measures of bone health in a National Institutes of Health-funded study conducted at Texas Tech University Health Sciences Center. They also improved muscular strength.
Tea reduced oxidative stress and inflammation, preventing the usual bone and muscle breakdown.
It can help your thinking. When your brain receives better blood flow and oxygen, and inflammation and oxidative stress are reduced, there is improved cognitive function, according to studies.
In fact, a 25 per cent reduction in impairments of activities of daily living was found when adults drank three to four cups of tea daily.
It can help you lose weight. Not only does tea have fewer calories than most beverages (zero without milk and sugar), but certain compounds in tea, and especially green tea, have been found to burn body fat.
Caffeine slightly increases fat-burning, but recent studies show "the combination of caffeine and green tea catechins (tea's antioxidants) is even more effective at increasing energy expenditure and fat oxidation, though the effect is small, burning 100 calories over 24 hours, or a loss of 2.8 pounds over 12 weeks," said Rick Hursel of Maastricht University, co-author of one study.
It can help you de-stress. An amino acid called L-theanine, in combination with caffeine, might reduce stress. Several studies have shown this combination, which occurs naturally in tea, reduces cortisol, the stress hormone, while improving mental alertness.
Tea is not a drug, which means the health effects are mild and might not even be noticeable, depending on your genetics.
That said, a wealth of evidence seems to show the British had the right idea. Perhaps it's time we all had a tea habit.
Katherine Tallmadge is a registered dietitian and author of Diet Simple: 195 Mental Tricks, Substitutions, Habits & Inspirations.