Nutritional significance of cyclodextrins: indigestibility and hypolipemic effect of alpha-cyclodextrin

Digestibility of alpha- and beta-cyclodextrin (CD) and nutritional consequences of alpha-CD and a CD mixture (n-dextrin, alpha-, beta-and gamma-CDs = 50, 30, 15 and 5% by weight) were investigated in rats. In contrast with beta-CD, alpha-CD was revealed to be indigestible. Growing rats were fed on diets supplemented with the CD mixture at 19.5, 39, 58.5 and 78% levels for 110 days, resulting in smaller weight gain and body fat deposition when they were fed on a higher CD diet. Rates of weight loss during the restricted feeding were faster in rats fed on a higher CD diet. These were due to food efficiency lowered by CD. Reduced serum and liver triacylglycerol (TG) levels were noted during a 110-day period of feeding of the CD diets, and the former was revealed due to a reduced hepatic-intestinal TG secretion rate. Rats fed on a 78% CD diet, which contained alpha-CD at the 24% level, showed abnormal symptoms such as poor appetite and constipation with gas accumulation in the large intestine, and some of them died during the first 2-week feeding period. However, the surviving animals showed adaptation to the diet in the later period of the 110-day feeding. These results suggest that alpha-CD may be classified as dietary fiber which can modulate lipid metabolism in rats. Furthermore, the CD mixture may be available as a calorie substitute for weight control, which may owe mostly to alpha-CD.