|
By David Blyweiss, M.D.
Several years ago, you couldn’t turn around without seeing yet another story about green tea. Since then, the media has shifted its focus to newer compounds like pomegranate, acai and vitamin D. But, while these are all worthy of our attention, we shouldn’t forget about the amazing health benefits green tea has to offer.
Most of these benefits of green tea can be traced back to two basic constituents: a family of antioxidants called catechins, which includes epigallocatechin-3-gallate (EGCG), and an amino acid known as L-theanine. EGCG and the other antioxidants in green tea protect against cell damage caused by oxidation. As a result, it lowers the risk of a number of different types of cancer. One way it does this, according to researchers at the University of Rochester Medical Center, is by binding to a protein called HSP90. This jams an important gene-damaging mechanism that can lead to the formation of cancer cells.
Tea may also help stymie cancer development by interacting with toxin-neutralizing enzymes in the liver and by encouraging apoptosis, a process that causes cells to die when their useful life is over. But EGCG’s talents extend well beyond cancer. This potent polyphenol also supports healthy cholesterol levels and protects the arteries against free radical damage.
L-theanine is an amino acid and is the other primary compound in green tea. It has neurotransmitter-like effects, and can improve mental focus and foster relaxation. Clinical trials show that L-theanine creates this sense of calm approximately 30 to 40 minutes after ingestion via at least two different mechanisms. First, this amino acid directly stimulates the production of alpha brain waves, creating a state of deep relaxation and mental alertness similar to what is achieved through meditation. Second, L-theanine is involved in the formation of the inhibitory neurotransmitter, gamma amino butyric acid (GABA). GABA influences the levels of two other neurotransmitters, dopamine and serotonin, producing the key relaxation effect.
L-theanine also has a significant effect on the release or reduction of neurotransmitters like dopamine and serotonin. This results in improved memory and learning ability. L-theanine may also influence emotions due to its effects on the increased release of dopamine. L-theanine also reduces brain serotonin concentration by either curtailing serotonin synthesis or increasing its degradation in the brain.
For most of us, the brain, heart and anti-cancer benefits of green tea would be enough to warrant drinking it on a regular basis. But, now researchers have discovered that the catechins in green tea just might help protect against glaucoma and other eye diseases, too. These results were from a preliminary study recently conducted at the Chinese University of Hong Kong and the Hong Kong Eye Hospital. The researchers found that the lens, retina and other tissues in the eye absorb significant amounts of green tea catechins after it is consumed. This, in turn, may protect the eyes against oxidative stress that can undermine vision.
So how much green tea do you need to drink to reap these ever-expanding health benefits? Most of the studies I’ve run across are based on drinking four to 10 cups a day. If green tea isn’t already your beverage of choice, that amount can be a bit much. In fact, most of my patients who drink green tea on a regular basis typically don’t sip more than three cups daily. Luckily, you can augment that amount by taking a whole foods green tea supplement that is standardized to contain a minimum of 40 percent catechins and 60 percent polyphenols. It’s the perfect way to ensure that you are getting all the healthy goodness green tea has to offer each and every day.
References:
Chu KO. Green Tea Catechins and Their Oxidative Protection in the Rat Eye. Journal of Agricultural and Food Chemistry, 2010; 58:1523.
Kim TI. l-Theanine, an amino acid in green tea, attenuates beta-amyloid-induced cognitive dysfunction and neurotoxicity: reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-kappaB pathways. Free Radical Biology & Medicine. 2009;47:1601-1610.
Yin Z. (-)-Epigallocatechin-3-gallate is a novel Hsp90 inhibitor. Biochemistry. 2009;48:336-345. |
