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in the human gastrointestinal tract, dietary ellagitannins are not absorbed
as such, but are hydrolyzed to yield ellagic acid, which is then further
metabolized by colonic microflora to more bioavailable derivatives
(Cerdá et al. , 2004, 2005).
8.4.4 Cancer prevention
A food-based approach utilizing berries concentrated by freeze-drying
has been extensively investigated in the prevention of esophageal and
colon cancer in rodent model systems (Stoner et al ., 2006, 2007). These
studies have used berries rich in ellagic acid (black raspberries and
strawberries), since pure ellagic acid had been shown to inhibit
chemically induced tumorigenesis in rodent esophagus. The freeze-dried
berries (10% in the diet) inhibited chemically induced cancer in the rat
esophagus by 30-60% and in the colon up to 80%. The berries affect
both the initiation and promotion/progression stages of tumor
development. So far, the results point to anthocyanins as the active
components, and the role of ellagitannins and other berry components are
under investigation. Several clinical trials are being conducted in patients
at high risk for esophagus and colon cancer. Patients with Barrett's
esophagus, esophageal dysplasia or colonic polyps consume freeze-dried
black raspberry powder daily, and various biomarkers of development of
the diseases are determined.
The effects of cloudberries on intestinal tumorigenesis have been
investigated in Apc -mutated Min mice. Although these mice develop
tumors mainly in the small intestine, they are used as an experimental
model for colon carcinogenesis. Freeze-dried cloudberries (10%) in a
modified rodent diet, with a composition and content of fat as in a typical
Western-type diet, prevented adenoma formation (Misikangas et al .,
2007). However, when cloudberry seeds and pulp were studied
separately, no effect on adenoma formation was observed (Päivärinta et
al. , 2006). One explanation for the lack of effect is the lower content of
ellagitannins in the seed and pulp diets; they were only half of that in the
whole cloudberry diet. Pure ellagic acid in the diet (1.5 g/kg) had no
effect on the number or size of adenomas in the distal small intestine, but
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