Colonic availability of apple polyphenols--a study in ileostomy subjects

Nutrition is thought to play an essential role in the pathogenesis of inflammatory and malignant gastrointestinal diseases. It is well known that plant ingredients such as polyphenols and flavonoids show anticarcinogenic effects both in vitro and in animal experiments, and may thus reduce the risk of colorectal cancer in man. The aim of the study was to determine the amount of polyphenols reaching the colon after oral intake of apple juice. After consumption of a polyphenol-free diet 11 healthy ileostomy volunteers drank 1 L of a polyphenol-rich cloudy apple juice. Ileostomy effluent was collected immediately before and 1, 2, 4, 6, and 8 h after consumption of apple juice. A broad spectrum of polyphenols was identified using HPLC-diode array detection (HPLC-DAD) as well as HPLC-ESI-MS/MS; quantitation was performed with HPLC-DAD. Most of the orally administered apple polyphenols were absorbed from or metabolized in the small intestine. Between 0 and 33% of the oral dose was recovered in the ileostomy bags with a maximum of excretion after 2 h. Phloretin glucuronide as product of polyphenol metabolism was detected in the ileostomy effluent. The present results show that most of the apple juice polyphenols are absorbed in the small intestine. Minor amounts of unmetabolized polyphenols are recovered in the ileostomy effluent, which would reach the colon under physiologic circumstances. These data have to be considered when polyphenols are used in model systems to show preventive effects in colorectal carcinogenesis.