Green Tea May Do Wonders for the Brain

17, 2006 -- Elders who drink green tea regularly may have sharper minds than those who don't drink green tea.

The finding comes from a Japanese study published in The American Journal of Clinical Nutrition.

The study included about 1,000 Japanese people aged 70 and older. Participants took tests of mental status including memory, orientation, ability to follow commands, and attention. They also told the researchers how often they drank beverages including green tea.

Those who reported drinking the most green tea were least likely to show cognitive impairment, based on their test scores, write Shinichi Kuriyama, MD, PhD, and colleagues.

Kuriyama works in the department of public health and forensic medicine at Tohoku University's medical school in Sendai, Japan.

How Much Green Tea Does It Take?
Drinking at least two daily cups of green tea was tied to the lowest risk of cognitive impairment in Kuriyama's study.

Compared with people who drank a cup of green tea up to three times weekly, those who drank two or more daily cups of green tea were 54% less likely to have test scores in the range of cognitive impairment.

Drinking green tea a little less often wasn't bad. People who drank a cup of green tea four to six times per week were 38% less likely to show cognitive impairment than those drinking green tea less than three times weekly.

Coffee, black tea, and oolong tea didn't show the same results. Green tea is a popular drink in Japan. More than seven in 10 participants reported drinking at least two cups of green tea daily.

Reading the Tea Leaves
The study doesn't prove that green tea deserves the credit for the elders' sharp minds.

The researchers didn't ask anyone to change their tea consumption for the study's sake. Instead, they checked test scores and tea habits.

Data was only gathered once. So it's not clear if participants' tea habits had lasted a lifetime or if their test scores changed over time.

Kuriyama's team considered factors linked to cognitive impairment, including diabetes, smoking, and advanced age. They also adjusted for potentially helpful habits, such as physical activity, social ties, consumption of fish and vegetables, and self-reported overall health.

Even after considering all those factors, high consumption of green tea was still associated with a lower risk of cognitive impairment, the study shows.

Next Steps
"To our knowledge, this is the first study to examine the association between consumption of green tea and cognitive function in humans," Kuriyama's team writes.

They note that natural compounds in green tea -- especially a chemical called EGCG (epigallocatechin-3-gallate) -- have shown promise in experiments on brain diseases in animals.

However, something else about green tea might help the brain, the researchers write.

For instance, people in Japan often socialize over green tea. Socializing could be good for the brain, note Kuriyama and colleagues.

They add that healthy people might be more likely to drink green tea. If so, those people would have a built-in brain advantage because of their general good health.

By Miranda Hitti
WebMD Health News

Reviewed by Louise Chang, MDFeb.

SOURCE: Kuriyama, S. The American Journal of Clinical Nutrition, Feb. 1, 2006; vol 83: pp 355-361.
© 2006 WebMD, Inc. All rights reserved.

Green Tea Fights Fat: Green Tea Ingredient May Promote Healthy Weight Loss

Jan. 26, 2005 -- Need another healthy reason to drink green tea? Aside from fighting heart disease, cancer, and other diseases, a new study shows that drinking green tea may also fight fat.

The study showed that people who drank a bottle of tea fortified with green tea extract every day for three months lost more body fat than those who drank a bottle of regular oolong tea.

Researchers say the results indicate that substances found in green tea known as catechins may trigger weight loss by stimulating the body to burn calories and decreasing body fat.

The findings appear in the January issue of the American Journal of Clinical Nutrition.

Green Tea: Fat Fighter?
Black tea, oolong tea, and green tea come from the same Camellia sinensis plant. But unlike the other two varieties, green tea leaves are not fermented before steaming and drying.

Most teas contain large amounts of polyphenols, which are plant-based substances that have been shown to have antioxidant, anticancer, and antiviral properties.

However, green tea is particularly rich in a type of polyphenols called catechins. These substances have also been shown to have anti-inflammatory and anticancer properties, but recent research in animals show that catechins may also affect body fat accumulation and cholesterol levels.

In this study, researchers looked at the effects of catechins on body fat reduction and weight loss in a group of 35 Japanese men. The men had similar weights based on theirBMI (body mass index, an indicator of body fat) and waist sizes.

The men were divided into two groups. For three months, the first group drank a bottle of oolong tea fortified with green tea extract containing 690 milligrams of catechins, and the other group drank a bottle of oolong tea with 22 milligrams of catechins.

During this time, the men ate identical breakfasts and dinners and were instructed to control their calorie and fat intake at all times so that overall total diets were similar.

After three months, the study showed that the men who drank the green tea extract lost more weight (5.3 pounds vs. 2.9 pounds) and experienced a significantly greater decrease in BMI, waist size, and total body fat.

In addition, LDL "bad" cholesterol went down in the men who drank the green tea extract.

The catechin content varies by amount of green tea used and steeping time. But general recommendations, based on previous studies on the benefits of green tea, are at least 4 cups a day. Green tea extract supplements are also available.

Researchers say the results indicate that catechins in green tea not only help burn calories and lower LDL cholesterol but may also be able to mildly reduce body fat.

"These results suggest that catechins contribute to the prevention of and improvement in various lifestyle-related diseases, particularly obesity," write researcher Tomonori Nagao of Health Care Products Research Laboratories in Tokyo, and colleagues.
A little extra support goes a long way when it comes to diet goals. Get the free help you need from WebMD!

By Jennifer Warner
WebMD Health News

Reviewed by Michael W. Smith, MD

SOURCE: Nagao, T. American Journal of Clinical Nutrition, January 2005; vol 81: 122-129.

© 2005 WebMD, Inc. All rights reserved.

Chemicals in Green Tea May Help With Memory and Learning Problems Associated With the Common Sleep Disorder

May 16, 2008 -- A cup of green tea may be just what the doctor ordered if you have learning and memory problems related to obstructive sleep apnea, the most common type of sleep-related breathing disorder.

Obstructive sleep apnea (OSA) starves the body of oxygen during sleep. Persons with the condition experience pauses in breathing while sleeping. This condition can cause a drop in oxygen levels, which can affect organs of the body. OSA increases your risk for high blood pressure, heart attacks, and strokes, and affects cognitive function such as learning and memory.

The powerful antioxidants found in green tea may help thwart such cognitive problems, according to a study published in this month's second issue of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine. Green tea contains compounds called polyphenols, which animal studies suggest can protect against neurodegenerative changes related to Parkinson's and Alzheimer's disease. Green tea polyphenols (GTP) work by counteracting oxidative stress in the brain. Oxidative stress is cell damage brought on by harmful molecules called free radicals. Antioxidants protect against this damage. Oxidative stress is believed to play a role in many diseases.

Signs of oxidative stress and changes in the brain have been documented among some patients with OSA, the study cites.

"OSA has been increasingly recognized as a serious and frequent health condition," study author David Gozal, MD, professor and director of Kosair Children's Hospital Research Institute at the University of Louisville, says in a news release. "A growing body of evidence suggests that the adverse neurobehavioral consequences imposed by [intermittent hypoxia] stem, at least in part, from oxidative stress."

The current study involved male rats that were intermittently deprived of oxygen during a 12-hour "night" cycle for two weeks. The intermittent oxygen deprivation was similar to that experienced by adults with OSA. The researchers gave half the rats water containing GTP and the other half plain water, and then tested the rats for markers of inflammation and oxidative stress.

After receiving the GTP cocktail or plain water drink, the rats entered a maze designed to test their spatial learning and memory abilities. In this case, the rats had to remember the location of a hidden platform.

The experiments showed that the rats treated with GTP made their way through the maze better than the other rats. The researchers say their findings suggest that the chemicals in green tea can calm learning problems related to OSA-induced hypoxia. They also found that there was chemical evidence of less oxidative stress in the rats given GTP.

GTPs "may represent a potential interventional strategy for patients" with sleep-disordered breathing," Gozal says.

Polyphenols are found in many foods and beverages, including tea, wine, and certain fruits and vegetables.

By Kelli Miller Stacy
WebMD Health News

Reviewed by Louise Chang, MD

SOURCES:

News release, American Thoracic Society.

Burckhardt, I. American Journal of Respiratory and Critical Care Medicine. May 2008: vol 177; pp 1135-1141.

© 2008 WebMD, LLC. All rights reserved.