Author: John C. Martin
Author Date: 5/5/2003

Giving your body a boost to fight off disease-causing bacteria and
viruses may be as simple as sipping tea. At least that is the
message from a group of medical investigators who reported findings
from a study in late April.(1)

Doctors at Harvard Medical School and Brigham and Womens Hospital in
Boston claim they have found a certain chemical in tea that can
dramatically boost the bodys defenses against disease.

The chemical, known as L-theanine, can prime immune system cells to
attack invading viruses, bacteria and fungi.

Jack Bukowski, M.D., Ph.D., a Harvard professor and rheumatologist
at Brigham and Womens Hospital, led the study in which L-theanine
was isolated in a test tube, and then assessed in a small group of
21 people.

Their results showed that drinking at least five cups of tea per day
helped boost the bodys immune system against invading microorganisms
by stimulating so-called gamma delta T-cells, which make up part of
the immune system.

Crucial for Defense Against Infection
L-theanine is broken down in the liver to ethylamine, one of a group
of molecules known as akylamines. "We found that akylamines
stimulated gamma delta T-cells, crucial for defense against
infection, and found that these molecules were shared by bacteria,
and by fruits and vegetables," Bukowski told Priority Healthcare. "L-
theanine, the precursor, was at very high concentrations in tea."

The healthy effects of tea are well documented. Studies have pointed
to the benefits of drinking tea after heart attack(3), cancer(4),
and other conditions(5,6).

"Tea has been touted as a healthful and medicinal beverage for
centuries" wrote Bukowski and his fellow researchers. "However, no
in vivo data demonstrating an immunologic effect on human tissue
have been published."

As opposed to in vitro analysis, in vivo studies are those conducted
in living animals or humans.

This may not be the first time you have heard of L-theanine. It is
sold as a dietary supplement to produce a feeling of relaxation,
lower blood pressure, and enhance sex drive.

Naturally, however, L-theanine is a substance found in green, black
and oolong teas. This study showed that L-theanine stimulated gamma-
delta T cells, the first line of defense when attacking bacteria,
viruses, fungi and parasites invade the body.(2)

In turn, the T cells can prompt the body to secrete natural
interferon, a key part of the chemical defense against infection.

Tapping Teas Treasures
Bukowski and his colleagues first tested the effect of bacteria
exposed to ethylamine in a test tube. Then, to advance their
theories about the effectiveness of L-theanine in humans, they asked
eleven volunteers to drink five cups of tea per day, and compared
the outcome to that of a group of 10 volunteers who drank coffee
over the same period. Before the test began, blood samples were then
taken from each individual.

After one month, the researchers took follow-up blood samples from
the tea drinkers, and then exposed it to E-coli bacteria. The
investigators reported that the immune cells in the blood samples
secreted five times more interferon than did blood cells from the
same subjects before the tea drinking experiment began. Blood and
bacteria tests from those who had drunk coffee showed there was no
change in interferon levels prior to, or after, the experiment.

The investigators pointed out that their findings are proof that
consuming tea, and perhaps other fruits and vegetables containing
akylamines may prime gamma delta T-cells into fighting off pathogens
or even tumors.

Bukowski said it may be possible to further isolate and refine L-
theanine from tea, and use that in a form of a therapy to boost the
bodys infection.

"L-theanine is more of a preventive," he explained. "Stronger
molecules such as biphosphonates stimulate the same cells, and have
immunostimulatory effects that are being leveraged to treat cancer."

In addition to tea-drinking, Bukowski says it is important to
remember what you eat every day. "I hope people eat more fruits and
veggies," he added, "since I believe other substances found within
[those foods] will also enhance immunity."

1. Kamath AB et al. Antigens in tea-beverage prime human V{gamma}2V
{delta}2 T cells in vitro and in vivo for memory and nonmemory
antibacterial cytokine responses. Proc Natl Acad Sci USA 2003 Apr 28;
[epub ahead of print].

2. Molne L et al. Role of gamma-delta T cell receptor-expressing
lymphocytes in cutaneous infection caused by Staphylococcus aureus.
Clin Exp Immunol 2003 May;132(2):209-15.

3. Mukamal KJ et al. Tea consumption and mortality after acute
myocardial infarction. Circulation 2002 May 28;105(21):2476-81.

4. Gao YT et al. Reduced risk of esophageal cancer associated with
green tea consumption. J Natl Cancer Inst 1994 Jun 1;86(11):855-8.

5. Hegarty VM, May HM, Khaw KT. Tea drinking and bone mineral
density in older women. Am J Clin Nutr 2000 Apr;71(4):1003-7.

6. Shiozaki T et al. Effect of tea extracts, catechin and caffeine
against type-I allergic reaction. Yakugaku Zasshi 1997 Jul;117
(7):448-54.