Green Tea: Vital Immune Support
Written by Nicole Crane BS, NTP
After water, green tea (along with its white and black variants) from the Camellia sinesis shrub, is the most consumed beverage in the world. There may be no beverage more salubrious. The tea plant is rich in valuable antioxidants known as polyphenols. The polyphenols in green tea are called catechins, of which EGCG (epigallocatechin gallate) is the most active and well known. Other beneficial compounds like the relaxation amino acid L-theanine and the energizing, mind sharpening alkaloids theobromine and theophylline may also be present. Green tea has numerous health benefits, from quelling the fires of inflammation to protecting healthy heart and brain function, from supporting immunity to improving metabolism while impacting blood sugar balance. This time of year, green tea piques the interest of anyone looking to keep the flu at bay, and the evidence is impressive.
How Does Green Tea Support Immunity?
Nobody wants their winter holiday season to be plagued with a cold or the flu. When you need a simple and effective immune boost, look towards green tea. This mighty leaf strengthens and supports the immune system in several significant ways. Green tea has long been recognized as having powerful antiviral properties. Tea actually alters the structure of the virus itself, which suppresses the ability of the virus to cause an infection. EGCG has the ability to attach to the cell membrane of the flu virus. EGCG binds to a glycoprotein on the flu virus called hemagglutinin, which blocks the ability of the virus to infect other cells.i This makes green tea a potent weapon against contracting the flu, and can aid in a quick recovery as well. Recent research shows that green tea also inhibits the neuraminidase enzyme slowing the spread from cell to cell of many viruses. Another component of green tea, L-theanine, has been shown to increase immune responses. L-Theanine activates and aids in the production of a type of white blood cell called gamma-delta-T lymphocyte ii , a quick acting immune cell that launches a mighty attack on invading pathogens like the flu virusiii . L-Theanine also helps to make interferon-gammaiv , an important cytokine (signaling protein of the immune system) that has powerful antimicrobial propertiesv . These immune cells are an essential part of the body's defenses against viruses and other invaders. By directly stimulating the action of the immune system and inactivating viruses, green tea offers unrivaled protection against illness.
The research on green tea and flu prevention and recuperation is exciting and notable. One study examined 197 healthcare workers over a period of 5 months during the winter. One group of 98 participants received green tea capsules containing 378 mg of catechins (supplying 270 mg of EGCG) plus 210 mg of L-Theanine. The control group with 99 participants received a placebo. The study participants were asked to report on the occurrence of flu like symptoms including fever plus at least one other symptom such as cough, sore throat, headache or body ache. In the green tea group far fewer got truly sick compared to placebovi . It showed that green tea offers more than 3-fold protection against contracting an illness, especially when exposure is significant.
Gargling with green tea also seems to offer significant protection. A study of elderly residents in a nursing home had subjects gargle with or without green tea catechins (60% EGCG) three times a day for three months. All participants had received a flu shot, but in the catechin group, only one participant out of 76 contracted the flu, while 5 subjects out of 48 in the control group got the flu.vii This means high catechin green tea improves the level of protection after immunization against the flu.
Green tea offers a plethora of benefits to the body and there are so many convenient ways to take it. Whether you choose to drink green tea (make sure it is organic!) or a liquid extract or in capsule form, it can go a long way to keep you healthy and well. Let green tea be your ally and avoid the flu this winter and for all winters to come.
i Nakayama, Mikio, et al. "Inhibition of the infectivity of influenza virus by tea polyphenols." Antiviral research 21.4 (1993): 289-299.
iii Rowe, Cheryl A., et al. "Specific formulation of Camellia sinensis prevents cold and flu symptoms and enhances γδ T cell function: a randomized, double-blind, placebo-controlled study." Journal of the American College of Nutrition 26.5 (2007): 445-452
v Bukowski, Jack F., and Susan S. Percival. "L-theanine intervention enhances human γδ T lymphocyte function." Nutrition reviews 66.2 (2008): 96-102.
vi Matsumoto, Keiji, et al. "Effects of green tea catechins and theanine on preventing influenza infection among healthcare workers: a randomized controlled trial." BMC complementary and alternative medicine 11.1 (2011): 15.
vii Yamada H, Takuma N, Daimon T, Hara Y. Gargling with tea catechin extracts for the prevention of influenza infection in elderly nursing home residents: a prospective clinical study. J Altern Complement Med 2006 Sep;12(7):669-72.
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