Alzheimer's & the Health Benefits of Green Tea

Green tea catechins, until recently thought to work simply as antioxidants, are now known to invoke a wide spectrum of neuroprotective cellular mechanisms. These include iron chelation, scavenging of free radicals, activation of survival genes and cell signaling pathways, and regulation of mitochondrial function. (The mitochondria are the energy production factories inside our cells. When they are not working properly, they generate many free radicals and little energy.) The end result is a significant lessening of damage to brain cells.

Iron accumulation in specific brain areas and free radical damage to brain cells are considered the major damaging factors responsible for a wide range of neurodegenerative disorders including both Parkinson's and Alzheimer's disease.

In the brain, epigallocatechin-3-gallate (EGCG) has been shown to act as an iron chelator, binding to and removing iron, thus preventing it from contributing to the production of free radicals. In addition to removing iron, EGCG also increases the activity of two major antioxidant enzymes, superoxide dismutase (SOD) and catalase, further helping to decrease free radical damage.

Another active compound in green tea, epicatechin (EC), reduces the formation of a protein called amyloid-beta. Plaque-like deposits of amyloid-beta in the brain are a defining characteristic of Alzheimer's disease.

-www.whfoods.org

Green Tea Keeps Elders Mentally Sharp: Research Showing Multiple Ways
Green tea helps slow the age-related decline in brain function seen as declining memory, cognitive impairment, dementia and Alzheimer's, shows a human study published in the February 2006 issue of the American Journal of Clinical Nutrition.

Researchers at Japan's Tohoku University studied 1003 subjects over age 70, comparing their green tea intake and mental sharpness, using a Mini-Mental State Examination, a well-accepted standardized test for measuring cognitive function.

Drinking more than 2 cups a day of green tea slashed odds of cognitive impairment in elderly Japanese men and women by 64%!

And at every level of cognitive impairment-from minimal to severe-those drinking the most green tea experienced significantly less mental decline than those drinking the least:

Compared with elderly Japanese who drank less than 3 cups a week, those drinking more than 2 cups a day had a 54% lower risk of age-related declines in memory, orientation, ability to follow commands and attention.

Those drinking 4 to 6 cups of green tea a week (1 cup a day) had a 38 lower risk of declines in brain function.

Green tea's primary protective agent is thought to be its catechin phytonutrient epigallocatechingallate or EGCG. Research shows this highly potent antioxidant:

• helps prevent the formation of B-amyloid, a protein whose accumulation is recognized as causing Alzheimer's (Basianetto S, Eur J Neurosci Jan 2006).
• protects brain cells by chelating (removing) iron, which might otherwise produce destructive free radicals (Reznichenko L, J Neurochem, March 2006).
• helps prevent oxidative stress-induced brain cell death by "talking" to brain cells' genes responsible for cell cycling and survival. Specifically, EGCG tells the genes in neurons to decrease production of caspase 3, an enzyme involved in initiating programmed cell death. (Park HJ, Life Sci Jan 2006; Levites Y. J Biol Chem, 2002)
• promotes memory-related learning ability by protecting cells in the hippocampus, a part of the brain involved in spatial cognition and memory-related learning ability, from free radical damage (Haque AM, J Nutr April 2006).

The body of research presented at the Symposium suggests tea may help maintain and improve brain health both directly and indirectly, said Dr. Greenwood, a Professor of Nutritional Sciences at the University of Toronto, a Senior Scientist at Baycrest in Toronto, and a leading authority on the relationship between diet and cognition.

"This new data adds to the growing evidence which shows that diet influences the likelihood and risk of an individual experiencing cognitive decline or dementia, including Alzheimer's Disease, with aging," said Canadian tea and health expert Dr. Carol Greenwood.

"The research shows that tea likely directly impacts brain health by maintaining brain cell function and by assisting in the repair of damaged cells," she said. "Drinking tea may further help because it reduces the risk of developing other disorders which increase the risk of cognitive decline and dementia."

"Dr. Mandel's work shows that tea may not only help prevent brain cells from dying, it appears that tea flavonoids may even rescue the neurons once they have been damaged, to help them repair," said Dr. Greenwood.

The latest findings on other potential health benefits of tea, including how it may play a role in shifting metabolism to favour weight loss and better manage blood sugar levels, were also unveiled at the Symposium. As well, other new studies which add to the existing body of knowledge about tea's potential ability to reduce risk for several chronic diseases were presented. These included research that shows tea flavonoids may improve cardiovascular health by reducing inflammation and improving blood vessel function.

All of these additional findings also support tea's potential role in preventing cognitive decline and dementia, said Dr. Greenwood. "The research shows that tea may help combat high cholesterol & atherosclerosis, type 2 diabetes and inflammation which are diseases and disorders that increase the risk of dementia."

Furthermore, she added, that tea's potential role in helping to maintain healthy body weight may also help prevent dementia because most of the diseases and disorders associated with risk for cognitive decline and dementia are more prevalent among with those with obesity.

Results from several ongoing human trials presented at the Symposium by Dr. John Foxe, Professor of Neuroscience, Biology and Psychology at City College of the City University of New York, found that theanine from tea actively alters the attention networks of the brain. Theanine is an amino acid present almost exclusively in the tea plant. After drinking tea, the amino acid theanine, which is present in Green, Black and Oolong varieties, is known to be absorbed by the small intestine and to cross the blood-brain barrier where it affects the brain's neurotransmitters, and increases alpha brain-wave activity. This alpha brain rhythm is known to induce a calmer, yet more alert, state of mind.

-Fourth International Scientific Symposium on Tea & Human Health, September, 2007

Chemical in Green Tea May Fight Alzheimer's
 An ingredient in green tea that researchers think might fight cancer may also protect the brain from the memory-destroying Alzheimer's disease, a study released Tuesday said. Scientists injected mice with an antioxidant from green tea called epigallocatechin-3-gallate (EGCG) and said it decreased production of beta-amyloid, a protein that forms the plaques that clog the brains of Alzheimer's victims. Several months of injections reduced plaque formation by as much as 54 percent, researchers from the University of South Florida wrote in the Journal of Neuroscience. The mice had been genetically programmed to develop an Alzheimer's-like disease.

-National Institute of Neurological Disorders and Stroke and the Alzheimer's Association, 9/20/2005

Drinking Tea Might Delay Alzheimer's Disease
3-4 cups of tea daily can improve the memory and help prevent Alzheimer's disease. The research team, based at Newcastle University's Medicinal Plant Research Center, investigated the properties of green and black tea, as well as coffee, in a series of laboratory experiments. The results showed that both types of tea inhibited the activity of enzymes associated with the development of Alzheimer's disease. Coffee, however, had no significant effect. In fact, drinking tea appears to affect the brain in a similar way as drugs prescribed for Alzheimer's disease the UK researchers report. According to scientists black and green brews fight enzymes that destroy chemical messengers in the brain. They said: "It's exciting as tea is popular and inexpensive without side effects."  

- Phytotherapy Research, August 2004

Green Tea - Alzheimer's, Parkinson's & Brain Injury
Both experimental and epidemiological evidence demonstrate that flavonoid polyphenols, particularly from green tea and blueberries, improve age-related cognitive decline and are neuroprotective in models of Parkinson's, Alzheimer's diseases and cerebral ischemia/reperfusion injuries. The article, in reference to 152 research publications, reviews the currently (Mar, 2004) established mechanisms involved in the beneficial health action and emerging studies concerning the putative novel molecular neuroprotective activity of green tea and its major polyphenol (-)-epigallocatechin-3-gallate (EGCG). 

-J Neurochem. 2004 Mar;88(6):1555-69 

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