We examined the effects of raw Chinese yam (
Dioscorea opposita), containing resistant starch (RS), on lipid metabolism
and
cecal fermentation in rats. Raw yam (
RY
)
and
boiled yam (BY) contained 33.9%
and
6.9% RS, respectively. Male Sprague-Dawley rats were fed a cholesterol-free, control (C) diet supplemented with or without 15
and
30 g of
RY
or BY/100 g for 3 wk. Plasma total cholesterol concentrations in the tail vein of rats fed the 30%
RY
diet were significantly lower than in the C group throughout the feeding period. Compared with the C group, non-HDL concentrations in arterial plasma in the 30%
RY
group was significantly reduced. Liver cholesterol concentration in rats fed the 30%
RY
diet was significantly higher compared with those fed the C diet. Hepatic cholesterol 7α-hydroxylase mRNA
and
fecal bile acid excretion were significantly higher in the BY, but not the
RY
group, compared with the C group. Fecal cholesterol excretion in the 30%
RY
group was greater compared with the C group. Hepatic microsomal triacylglycerol transfer protein mRNA was significantly lower in the 30%
RY
group compared with the C group. Cecal pools of acetate, propionate
and
butyrate were 113-257%, 181-476%
and
410-789% greater in the
RY
group compared with the C group. These results suggest raw yam is effective as a source of RS
and
facilitates production of short chain fatty acid (SCFA), especially butyrate, in the rat cecum. In addition,
RY
has a plasma-cholesterol lowering effect, possibly due to the inhibited release of VLDL.
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