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Hoeveel groene thee?*

Recente onderzoeken hebben aangetoond dat groene thee ook al goed is tegen reumatische artritis en voor de gewrichten. Tot op heden zeggen onderzoekers altijd dat 8-10 koppen groene thee per dag o.k. is. Uit een nieuw onderzoek blijkt nu dat gedurende lange tijd hoge dosis polyfenolen uit groene thee wellicht minder gezond kunnen zijn voor de lever en de nieren. Omdat vooral in groene thee extracten wel 50x meer polyfenolen kunnen zitten dan in de gewone thee lijkt het oppassen met het  langdurig gebruik van deze extracten. Uit het onderzoek bleek wel dat de mogelijke lever- en nierschade na het stoppen met de inname van de grote hoeveelheden groene thee verdween.

Can You Have Too Much Green Tea?

In a recent study published last month, researchers reported that green tea may help ease the inflammation and pain of rheumatoid arthritis.  In that study, isolated synovial joint cells were treated with the active compound in green tea, called epigallocatechin-3-gallate (EGCG).  The cells were then stimulated with a protein called cytokine interleukin-1 beta or IL-1B, known to cause cartilage in the joint to break down.  The same team also reported EGCG has the ability to block the activity of two potent molecules, IL-6 and cyclooxygenase-2 (Cox-2), which also play a role in breaking down bone in an RA joint.  In addition, it blocked the production of prostaglandin E2, another compound that can cause joint inflammation.  This research supports other research showing that green tea may help protect against certain autoimmune diseases, such as Sjogren’s Syndrome and Lupus.
One researcher suggested that people try drinking three or four 8-ounce cups of green tea per day, drinking it continuously throughout the day.  Others have suggested that 8-10 cups per day is ok. There are also green tea supplements on the market, purporting to give extra benefits of green tea in more concentrated doses.
But new research and articles are raising a caution to people who drink green tea or use the supplements, since the current research has not determined how much tea is safe for consumptions.  This research (published in Chemical Research in Toxicology, vol. 20) has found that ingesting too much green tea, especially in supplement form can cause liver and kidney damage. 
Green tea contains polyphenols, the antioxidant compounds in green tea that help rid the body of free radicals (chemical reactive atoms or molecules that damage cells).  But this new study found that ingesting too much of these polyphenols causes liver toxicity.  This is a higher risk for people who take green tea supplements, because the supplements can contain as much as 50 times the amount of polyphenol as a cup of tea.  While even someone who drinks 8-10 small cups of green tea a day will probably be fine, the supplements pose more risk. Extract
(Juni 2007)