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Thee versterkt immuunsysteem.*
Volgens een Amerikaans onderzoek zou thee het immuunsysteem
versterken en mensen beschermen tegen infecties.
De onderzoekers lieten een aantal proefpersonen gedurende vier weken vijf koppen
gewone zwarte thee per dag drinken. Nadien werd hun bloed blootgesteld aan
E-coli bacteriën. Bleek dat bij de theedrinkers vijf keer meer interferon, een
natuurlijke afweerstof, werd gevonden in vergelijking met proefpersonen die
koffie hadden gedronken.
Basis van het effect is een stof L-theanine die voorkomt in gewone theebladeren
en die een stimulerend effect heeft op bepaalde T-cellen die deel uitmaken van
ons immuunsysteem, die op hun beurt de productie van interferon stimuleren. Op
basis hiervan besluiten ze dat vijf kopjes thee per dag (zowel zwarte als groene
thee) een effectieve bescherming tegen bacteriële, virale en schimmelinfecties
biedt.
Drinking tea appears to boost the immune system, perhaps helping people fight off or blunt the effect of infections, researchers said Monday. Non-tea drinkers who downed five to six small cups of black tea per day for two weeks appeared to be better able to fight off bacterial infections, according to the report. As an explanation for tea's benefits, experiments in the lab revealed that an ingredient found in black, green, oolong and pekoe teas boosted the ability of immune system cells to attack a bacterial invader. The experiments used ethylamine, which is produced when the tea ingredient L-theanine is broken down in the liver. Previous research suggests that ethylamine, which is also found in vegetables and wine, may target other pathogens as well, including parasites, viruses, and perhaps tumors. Based on these findings, people looking to ward off diseases might want to add certain teas to their menu, study author Dr. Jack F. Bukowski of Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts. "I think the elderly would benefit a lot from drinking tea," he said. "I think there's no downside to it." However, he added that regular tea drinkers still get sick, so people should not throw out their medicine cabinet or tell off their doctors just yet. "Drinking tea isn't a treatment or a cure for anything," Bukowski cautioned. "Probably most (tea drinkers) will still get sick. But people who do get sick will probably get a milder case," he said. The study findings appear in the online early edition of the Proceedings of the National Academy of Sciences. During the study, Bukowski and his colleagues measured the activity of immune system cells called gamma delta T cells in people who normally did not drink tea. Gamma delta T cells are an arm of the immune system charged with preventing and cushioning the blow of diseases. Previous experiments have shown that exposing these cells to ethylamine boosted the abilities of the cells to fight infections. During the study, Bukowski and colleagues extracted gamma delta T cells from people and exposed them to ethylamine. After the cells were mixed with bacteria, the researchers saw that those that had not been exposed to ethylamine mounted no attack against the bacteria. However, cells that had been previously exposed to the tea component multiplied by 10-fold, and therefore produced larger amounts of a chemical that fights bacteria. And in experiments with people, the researchers found that after drinking about 20 ounces of tea a day for two weeks, people's gamma delta T cells produced a wealth of anti-bacterial chemicals when exposed to bacteria. In contrast, people who drank coffee instead of tea during the study produced no disease-fighting proteins in response to bacteria. Despite the supposed power of tea to fight infection, Bukowski urged people to maintain a healthy perspective on the findings."If people are sick, they shouldn't start drinking tea to get better," he said. "They should go to the doctor." SOURCE: Proceedings of the National Academy of Sciences 2003;10.1073/pnas.1035603100.