Apple pectin and a polyphenol-rich apple concentrate are more effective together than separately on cecal fermentations and plasma lipids in rats

To evaluate the effect of apple components on cecal fermentations and lipid metabolism, rats were fed diets containing 5 g/100 g apple pectin (PEC), 10 g/100 g high polyphenol freeze-dried apple (PL) or both (PEC + PL). The cecal pH was slightly acidic (6.49) only in rats fed the PEC + PL diet (controls, 7.02). The cecal short-chain fatty acid pool was enlarged by all the apple fractions, with a peak of 560 micromol in rats fed the PEC + PL diet compared with 189 micromol in controls. Butyrate concentrations were 2-fold greater in rats fed the PL diet than in controls. Substantial concentrations of galacturonate and succinate (approximately 40 mmol/L) were found in the cecum of rats fed the PEC diet and, to a lesser extent, the PEC + PL diet. The PEC + PL diet significantly lowered plasma cholesterol, whereas both the PL and PEC + PL diets lowered plasma triglycerides. Liver cholesterol and triglyceride concentrations were lower in rats fed the PEC and PEC + PL diets. Fecal bile acid excretion was markedly reduced, whereas sterol excretion was significantly increased by dietary PEC. Rats fed the PEC and PEC + PL diets also had lower apparent cholesterol absorption than controls (30 compared with 43%). In conclusion, apple pectin and the polyphenol-rich fraction were more effective when fed combined together than when fed separately on large intestine fermentations and lipid metabolism, suggesting interactions between fibers and polyphenols of apple.