Arnaud Messager

Effects of soluble corn bran arabinoxylans on cecal digestion, lipid metabolism, and mineral balance (Ca, Mg) in rats

The effects of soluble corn bran arabinoxylans on cecal digestion, lipid metabolism, and mineral utilization [calcium (Ca) and magnesium (Mg)] were investigated in rats adapted to semipurified diets. The diets provided either 710 g/kg wheat starch alone (control) or 610 g/kg wheat starch plus 100 g/kg corn soluble fiber (arabinoxylans) and either 0 or 2 g/kg cholesterol (control + cholesterol and arabinoxylans + cholesterol, respectively). Compared with rats fed the control diets, rats fed the arabinoxylan diets had significant cecal hypertrophy (+50% after 3 days of the fiber adaptation) and an accumulation of short-chain fatty acids, especially propionic acid (up to 45% in molar percentage). Arabinoxylans enhanced the cecal absorption of Ca and Mg (from 0.07 to 0.19 micromol/min for Ca and from 0.05 to 0.23 micromol/min for Mg). Mg balance was enhanced by arabinoxylans (+25%). The arabinoxylan diet markedly reduced the cholesterol absorption from 50% of ingested cholesterol in controls up to approximately 15% in rats adapted to the arabinoxylans diet. Arabinoxylans were effective in lowering plasma cholesterol (approximately -20%). There was practically no effect of the diets on cholesterol in d > 1.040 lipoproteins (high density lipoproteins) whereas arabinoxylans were very effective in depressing cholesterol in d < 1.040 lipoproteins (especially in triglyceride-rich lipoproteins). Corn fermentable fiber decreased the accumulation of cholesterol in the liver. In parallel, the arabinoxylan diet counteracted the downregulation of 3-hydroxy-3-methylglutaryl-CoA by cholesterol. These data suggest that arabinoxylans may have a great impact on intestinal fermentation, mineral utilization, and cholesterol metabolism.

Making bread with sourdough improves mineral bioavailability from reconstituted whole wheat flour in rats

OBJECTIVE We compared the effects of different kinds of bread fermentation on mineral bioavailability. METHODS Wistar rats were fed one of the following experimental diets for 21 d: control, reconstituted whole wheat flour (white flour plus bran), yeast bread, and sourdough bread. The apparent mineral absorption and intestinal fermentation were measured in each animal. RESULTS Phytate contents in yeast and sourdough bread were lower than in reconstituted whole wheat flour (-52% and -71%, respectively). Total cecal pool of short-chain fatty acids, in particular the butyrate pool, was significantly increased by the ingestion of unrefined products. Calcium homeostasis was not modified by these nutritional conditions, whereas magnesium absorption was significantly greater in rats fed the control and sourdough diets than in those consuming whole wheat flour and yeast bread. Magnesium kidney excretion was slightly stimulated by sourdough bread. Compared with the control diet, iron balance was significantly reduced by reconstituted whole wheat flour diet. Yeast bread making counteracted the deleterious effects of whole wheat on iron absorption, whereas sourdough bread making enhanced iron absorption. Further, liver and plasma iron and transferrin saturation levels were lower in rats adapted to the flour diet than in other groups. Zinc absorption was strongly depressed in the presence of unprocessed reconstituted whole wheat flour in the diet, but yeast fermentation afforded a zinc assimilation comparable to the control diet, whereas the sourdough bread led to maximal zinc absorption. Copper absorption increased significantly when rats were fed the sourdough bread, whereas unprocessed whole flour depressed copper absorption (-41% versus control diet). CONCLUSION Mineral bioavailability from reconstituted whole wheat flour can be improved by bread making. Although yeast fermentation minimizes the unfavorable effects of phytic acid, sourdough bread is a better source of available minerals, especially magnesium, iron, and zinc.

Wheat Varie1y has a Maior Influence on Mineral Bioavailability; Studies in Rats

The aim of this study was to compare mineral bioavailability of four soft wheat varieties (Soissons, Hardi, KON2, BNC) in rats. If intestinal fermentation was stimulated by four diets compared to control diets, the incorporation of 70% of whole wheat flour in the rat diet did not modify Ca bioavailability. Nevertheless, Mg absorption and accumulation in bone were stimulated by the ingestion of KON2 and BNC varieties. Feeding KON2 or BNC varieties significantly increased iron absorption and status compared to the other three groups. Zinc absorption was significantly depressed by Soissons flour (- 28% ), whereas the three other whole wheat flour diets led to a better zinc assimilation compared to the control group. The consumption of Hardi, KON2 or BNC wheat varieties had percussions on liver zinc ( + 29%, + 36% and + 33% compared to control group, respectively). Copper absorption was significantly increased by KON2 or BNC varieties ( + 93% and + 88%, respectively), but copper status was not modified by nutritional differences. Moreover, phytate breakdown was higher when the diets contained KON2 or BNC varieties. Mineral bioavailabilities from KON2 or BNC varieties were higher than those observed with Soissons or Hardi varieties. Thus, genetic origin plays a major role in determining mineral bioavailability in whole wheat.