Rice bran oil, not fibre, benefits cholesterol levels
Rice bran oil, being used by some US restaurants to eliminate trans fats, appears to be responsible for the cholesterol-lowering effect of the ingredient rather than its fibre content, say researchers.
They also found that unsaponifiable compounds in the oil, rather than fatty acids, are likely producing this effect.
This gives the oil similar properties to plant sterols used increasingly in food products designed for cholesterol reduction.
Researchers at Louisiana State University carried out two studies to test which element of rice bran was responsible for a widely known benefit on cholesterol levels.
In the first study they gave 26 healthy adults with moderately raised cholesterol levels a daily diet containing 1322g dietary fibre for three weeks. Then 13 of the volunteers were switched to a diet with defatted rice bran to double the fibre intake for five weeks.
In a second, randomized, crossover study over 10 weeks, 14 volunteers consumed a diet with rice bran oil (a third of the total dietary fat), which was then substituted for an oil blend that had a fatty acid composition similar to that of the rice bran oil.
The defatted rice bran did not lower lipid concentrations, the researchers report in this months American Journal of Clinical Nutrition (vol 81, no 1, pp 64-68).
In the second study, total cholesterol was significantly lower with consumption of the diet containing rice bran oil than with consumption of the control diet.
"There were no substantial differences in the fatty acid composition of the diets; therefore, the reduction of cholesterol was due to other components present in the rice bran oil, such as unsaponifiable compounds, write researchers.
Consumption of the rice bran oil diet led to a 7 per cent decrease in LDL cholesterol.