In the latte-obsessed United States, tea is gaining ground as scientists and the public learn more about its benefits.
A growing body of research suggests that the worlds second-most-consumed beverage – only water is more popular – helps prevent cardiovascular disease, burn calories and ward off some types of cancer.
We dont clearly understand why tea is so beneficial, but we know it is, said Thomas G. Sherman, an associate professor in the Department of Pharmacology and Physiology at Georgetown University Medical Center.
There are lots of epidemiological studies, and so of course people see these studies and want to drink tea and gain these benefits.
Nationally, tea purchases have risen for 20 consecutive years, annual supermarket sales have surpassed $2.2 billion, and away-from-home consumption of tea has grown by at least 10 percent a year for a decade, according to the Tea Association of the USA, a New York-based industry group. On any given day, the association says, 160 million Americans drink tea.
Although coffee is still king in the United States, change is brewing. Department of Agriculture statistics show tea drinking has increased as coffee drinking has declined: Per-person tea consumption was nine gallons in 2009, up from 7.3 gallons in 1980; per-person coffee consumption was 23.3 gallons in 2009, down from 26.7 gallons in 1980, about half what it was in the mid-1940s.
And while studies also show that coffee is associated with many health benefits, including helping protect against diabetes and Parkinsons disease, a typical cup has much more jitter-producing caffeine than tea does.
Manelle Martino, co-owner of Capital Teas in Washington, said she has seen the explosion of interest in tea firsthand. Her sales of loose-leaf tea have risen substantially each year since she opened the business in 2007, she said.
People are becoming more health-conscious, she said. You have baby boomers who are into preserving their youth. You see them wanting to take better care of themselves.
Tea comes from the leaves of the warm-weather evergreen Camellia sinensis, and it is classified into five types: black, white, green, oolong and puerh.
Experts say all are healthful. Many scientists link health benefits to teas polyphenol antioxidants, which protect against oxidative stress, but others say they dont know exactly which chemicals or combinations of chemicals in tea produce the benefits.
Sherman, for example, said theres no evidence connecting teas antioxidants to beneficial effects, and he pointed to a study showing that black tea reduces LDL, or bad, cholesterol without affecting antioxidant levels, suggesting something else in tea is causing this.
Numerous epidemiological studies – which establish correlation, not cause and effect – focus on teas role in reducing cardiovascular disease, the nations biggest killer.
A 2004 paper in the Archives of Internal Medicine, for instance, looked at hypertension rates among people who drank tea for at least a year. The study, conducted in Taiwan, found that those who drank four to 20 ounces of tea a day had a 46 percent lower risk of developing high blood pressure than people who didnt drink tea regularly.
Another paper, published in 2002 in the American Journal of Clinical Nutrition, culled through the results of a large study concerning chronic disease and found that people drinking the greatest amount of tea – more than 12 ounces a day – had barely half the risk of heart attack as people who did not drink tea.
More recent cardiovascular research was presented last fall at the Department of Agriculture in Washington. One study found that black tea reduced blood pressure in all participants and counteracted the detrimental effects of high-fat meals in people with high blood pressure.
The more tea you drink, the better, Sherman said. Its astounding, really.
As for cancer prevention, the evidence is less compelling. Studies have suggested that green tea consumption helps prevent several cancers, but studies of its effect on breast cancer among Asian women yielded conflicting results.
Studies have also examined whether tea affects weight loss. One, from 2004, found that caffeine, theanine and perhaps other components in green tea powder suppressed weight gain and fat accumulation in laboratory mice.
There is also some evidence that drinking tea promotes digestive health generally. Gerry Mullin, an associate professor of medicine at Johns Hopkins School of Medicine and author of The Inside Tract: Your Good Gut Guide to Great Digestive Health, said tea appears to help control glucose and insulin and keep the gastrointestinal system running well.
These teas are anti-inflammatory in nature. They have anti-bacterial properties, Mullin said. They boost the immune system and provide a lot of different benefits.
A little advice
For Shermans wife, Guinevere Eden, the healthy brew stirs memories of her childhood in England.
First thing in the morning, it feels so good, said Eden, who drinks five or six cups over the course of a day.
Tea experts disagree on how much tea to recommend for better health. Some say two eight-ounce cups a day, while others say five or more cups.
Experts said teas relatively low caffeine levels make it possible to drink large amounts without the jitters, fast heartbeat and stomach upset that the same amount of coffee would probably induce. Black tea, which has more caffeine than green, oolong or white teas, has about half the caffeine of coffee.
Still, experts advise against overdoing it, noting that tea, unlike coffee, contains trace amounts of aluminum. But according to the National Cancer Institute, while aluminum can accumulate in the body and cause neurodegenerative disorders, theres no evidence of aluminum toxicity associated with drinking tea.
Sherman said iced tea should provide the same benefits as hot tea, as long as it starts out as hot and is then cooled, not just brewed in the sun or made from store-bought powdered mixtures.
He said adding milk to tea may make it less beneficial, since theres some evidence that protein in milk binds to the healthful chemicals in tea and prevents them from being absorbed. Sugar doesnt seem to reduce teas benefits, he and others said, although it comes with problems of its own, such as empty calories that can lead to weight gain.
Martino, of Capital Teas, said customers at her shops often ask about health benefits, especially after pronouncements by celebrity physicians such as Mehmet Oz. Whenever Oz mentions a certain tea, Martino said, people come flooding in looking for that tea.
Erika Sanchez, a manager at the Teaism shop in Washington, said customers do much the same at her shop – and then discover how many different types of teas are out there.
If youre new to the tea world, it can be surprising, she said.
Americas rising interest in tea has been attracting international attention.
Sundeep Mukherjee, principal adviser to the Darjeeling Tea Association, said three-quarters of the tea from that region of India is exported, with up to 10 percent going to the United States, a portion thats been rising over the last decade as health benefits become more widely known.
The tea industry is doing well, Mukherjee said. This is a product everyone drinks.