Dietary supplementation with 0.5 and 1% blueberry anthocyanins was associated with 37 and 66% increases in bile acid excretion, according to data published in the European Journal of Nutrition.
Researchers from The Chinese University of Hong Kong also proposed a second mechanism involving an effect on gene expression linked to enhanced excretion of sterols, with sterol excretion increased by between 24 and 30%.
The doses used in this study were equivalent to 2,500 mg of anthocyanins in a 2,000 calorie diet, which is above the 900–1,800 mg per 2,000 calories doses recommended by supplement manufacturers, said the researchers.
“In this regard, the concentration of blueberry anthocyanins used in the present study could achieve its cholesterol-lowering activity under the normal physiological conditions in humans if the data could be extrapolated to humans,” they wrote.
“In addition, such high doses used in the present study had an advantage because it could maximize the biological activity of blueberry anthocyanins so that the underlying mechanisms could be thoroughly investigated.”
Blueberries, nature's only 'blue' food, are a rich source of polyphenols, potent antioxidants that include phenolics acids, tannins, flavonols and anthocyanins.
The berries are said to have a number of positive health effects, including cholesterol reduction, and prevention against some cancers and neurodegenerative diseases such as Alzheimer's.
The popularity of the berry has increased in recent years with the publication of more science supporting its health benefits, and an overall consumer move towards 'superfruits' and all things 'antioxidant'.
For the new study, the Hong Kong-based scientists supplemented the diet of hamsters with 0, 0.5 and 1.0 % blueberry anthocyanins for six weeks.
Results showed that both groups of animals fed with the blueberries displayed decreased total cholesterol levels of between 6 and 12%, in addition to the increase in in bile acid excretion and in the excretion of sterols.
The researchers proposed that the “cholesterol-lowering activity of blueberry anthocyanins was most likely mediated by enhancing the excretion of sterols accompanied with down-regulation on gene expression of [select] intestinal [genes].”
“In view that excess cholesterol in mammals is usually disposed via biliary excretion or by conversion to bile acids, the results suggest that based on the significant increase in bile acid excretion, this may be a primary mechanism,” they wrote.
Source: European Journal of Nutrition
Published online ahead of print, doi: 10.1007/s00394-012-0393-6
“Blueberry anthocyanins at doses of 0.5 and 1 % lowered plasma cholesterol by increasing fecal excretion of acidic and neutral sterols in hamsters fed a cholesterol-enriched diet”
Authors: Y. Liang, J. Chen, Y. Zuo, K.Y. Ma, Y. Jiang, Y. Huang, Z-Y. Chen