 Magic beans fight diabetes
A diet rich in black soya beans could help control weight, lower fat and cholesterol levels, and aid in the prevention of diabetes, reports Lisa Richards |
 A new study in rats reveals that a diet rich in black soya beans could help control weight, lower fat and cholesterol levels, and help in the prevention of diabetes. Yellow soya beans already feature prominently in western diets, whereas black soya beans are more commonly associated with oriental medicine.
Previous laboratory studies suggest that the makeup of black soya beans should make them more potent than yellow soya beans at preventing cholesterol buildup (Journal of Agricultural Food and Chemistry 2005, 53(11), 4578). Now a team of Korean researchers has shown that this is indeed the case, at least in rats, and that eating black soya also prevents weight gain (Journal of the Science of Food and Agriculture, February 2007 doi: 10.1002/jsfa2808).
The researchers, led by Shin Joung Rho at Hanyang University, Seoul, allowed 32 rats to gorge on a fatty diet. The rats were divided into four groups. Three groups obtained two, six and 10% of their energy from black soya protein and a control group did not get any black soya.
After two weeks, those getting 10% of their energy from black soya had gained half as much weight as those in the control group. Total blood cholesterol fell by 25% and LDL (so-called bad) cholesterol fell by 60% in the rats in the 10% group.
The mechanism of action of the black soya is unclear. But David Bender, sub-dean at the Royal Free and University College Medical School, London, thinks that the soya protein may be having an effect on fat metabolism in the liver and adipose tissue, reducing synthesis of new fatty acids and cholesterol. (This differs from the action of obesity drugs such as Roche’s Xenical, which simply inhibit absorption and digestion of dietary fat.)
It is this metabolic effect that may explain the traditional (oriental) use of black soya in the treatment of diabetes. ‘The key problem in type II diabetes is impairment of insulin action, mainly as a result of excess abdominal adipose tissue – so loss of weight often improves glycaemic control,’ said Bender. But he still doubts whether black soya will be a useful treatment for obesity. ‘If food intake is greater than energy expenditure then the excess will have to be stored somehow, and that will be storage as fat – even if the black soya is inhibiting fatty acid synthesis to some extent.’
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