Relationship between fermentations and calcium in the cecum of rats fed digestible or resistant starch.

The present studies were undertaken to investigate the effects of the dietary calcium (Ca) level on the Ca balance and on large intestine physiology in rats fed diets providing carbohydrate as digestible wheat starch (DS) or resistant starch (RS). Resistant starch was a high-amylose maize starch. The Ca level ranged from a marginally sufficient level (3 g/kg) to a level in excess of nutritional requirements (6 g/kg). The cecal fermentations were more developed in rats fed RS diets and they were affected by the dietary Ca level, compared to rats fed the DS diets. In rats fed a low Ca RS diet, the cecal fermentations were more acidic than with a high Ca level and there was an accumulation of lactic acid together with depressed concentrations of short-chain fatty acids. There was a considerable accumulation of Ca and phosphate (Pi) in the cecum of rats fed the 6 g/kg level; on the other hand, the concentrations of minerals (Ca, Pi) were very low in the cecum of rats fed the low Ca RS diet. The proportion of soluble Ca in the cecum was markedly enhanced by active fermentations, especially in rats fed the high Ca RS diet (16.3 mmol/l). In rats fed the RS diet, there was a substantial absorption of Ca from the cecum, which was relatively proportional to the dietary Ca level. The above data suggest that in these rats, Ca absorption in the large intestine made a substantial contribution to the digestive balance, probably at the expense of absorption in the upper part of the intestine.(ABSTRACT TRUNCATED AT 250 WORDS)