Effects of Taiwanese yam ( Dioscorea japonica Thunb var. pseudojaponica Yamamoto) on upper gut function and lipid metabolism in Balb/c mice

This study investigated the effects of a Taiwanese yam, Dioscorea japonica Thunb var. pseudojaponica Yamamoto, on upper gut function and lipid metabolism in adult Balb/c mice. Mice were randomly allocated to consume the control, 25%, or 50% yam diet in which yam in an uncooked lyophilized form was incorporated into the diet for 21 d. Growth rates were similar among groups, even though the apparent protein absorption rate was decreased by the 50% yam diet. Both yam diets decreased gastric villous width but did not significantly modulate other morphologic and proliferative indices. Brush-border leucine aminopeptidase activities in the small intestine were increased approximately 30% by the 25% and 50% yam diets, respectively. In contrast, sucrase activity was decreased 40% by the 25% yam diet and 50% by the 50% yam diet. The 50% yam diet consistently improved the cholesterol profile in the plasma and liver, whereas the 25% yam diet reduced only the level of low-density lipoprotein cholesterol in plasma. Changes in blood lipid levels were associated with reduced fat absorption. A 25% uncooked yam diet may benefit upper gut function and prevent hypercholesterolemia in humans, but the 50% yam diet negatively affected protein absorption.