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Green Tea
and Bioavailability of Catechins
Researchers can
easily determine the catechin content of a given cup of green tea.
What’s not so easy is determining how many of those catechins actually
make it through the digestive system and into the bloodstream -- in
scientific terms, their "bioavailability." Unfortunately, the catechins
are rather unstable in non-acidic environments like the intestines and a
great many of them “bite the dust” before they can do your body any
good. But can the catechins be protected when combined with certain
additives? In 2007, researchers from the Department of Food Study at
Purdue University looked into the topic and published their findings in
Molecular Nutrition and Food Research.
For the study, the
researchers prepared a beverage containing specific amounts of four green tea
catechins (EC, EGC, EGCg and ECg). The beverage was then mixed with common
commercial beverage additives, including citric acid, BHT, EDTA, ascorbic acid
(vitamin C), milk (bovine, soy and rice) and various types of citrus juice
(orange, grapefruit, lemon and lime). Each mixture was then subjected to
simulated digestion -- a recreation of the conditions in the stomach and small
intestines.
When no additives were
included, less than 20 percent of the catechins remained after digestion.
Bovine, soy and rice milk increased catechin recovery 52% - 69%, while ascorbic
acid increased it as much as 82%. But adding citrus juice (lemon, orange,
grapefruit or lime) was the real winner – increasing the recovery of some
catechins by as much as 98%!
The study doesn't say if
the citrus juice was fresh or bottled, although it seems both should work since
their nutritional value is much the same. However, fresh citrus juice can have
almost twice as much vitamin C as the bottled kind. And since vitamin C
(ascorbic acid) has a stabilizing effect on catechins, fresh juice might be your
best choice.
Green RJ, Murphy AS, Schulz B, et al. Common tea formulations modulate in vitro
digestive recovery of green tea catechins. Mol Nutr Food Res
2007;51(9):1152-62.
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Nadine Taylor, M.S., R.D. presents
GreenTeaLibrary.com, the most
comprehensive collection of scientific information describing the
health benefits of green tea.
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