Scientists based in Wisconsin have identified the mechanism behind buckwheat protein's ability to reduce cholesterol absorption by about half.
The research, published in the Journal of Agriculture and Food Chemistry, used model Caco-2 cells to model absorption of cholesterol in the presence and absence of buckwheat protein and found that cholesterol absorption was cut by 47 per cent.
"We looked at how buckwheat protein modulated cholesterol uptake in Caco-2 cells from micelles to better understand a possible mechanism of action in the gut," said lead author Brandon Metzger, from Standard Process and the University of Wisconsin.
"When we conducted the cholesterol binding experiments in vitro, we found that a large proportion of the cholesterol was associated with an insoluble fraction of buckwheat protein."
High cholesterol levels, hypercholesterolaemia, have a long association with many diseases, particularly cardiovascular disease (CVD), the cause of almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
The new in vitro study looked at how protein from buckwheat (Fagopyrum esculentum Moench) could disrupt the solubility of micellular cholesterol with Caco-2 cells.
Metzger and co-workers incubated the buckwheat protein (0.2 per cent) with cholesterol and micelle lipid components before the formation of micelles, and found that cholesterol solubility was reduced 40 per cent.
However, when the protein was incubated after the formation of micelles, the solubility of the cholesterol was not reduced.
Dietary cholesterol is absorbed by combining with bile salts to form bile salt micelles, which can then be taken up by the cells lining the intestine. By inhibiting the absorption of these micelles, the cholesterol is excreted from the body.
While the buckwheat protein conferred benefits, buckewheat flour did not significantly affect cholesterol solubility, said the researchers.
Comparison with other protein sources showed that the buckwheat protein inhibited cholesterol to a greater extent. Indeed, bovine serum albumin, casein, and gelatin reduced cholesterol uptake by 36, 35 and 33 per cent, respectively, compared to 47 per cent for the buckwheat protein.
"Reduction in cholesterol uptake in Caco-2 cells was dose-dependent, with maximum reductions at 0.1-0.4 per cent buckwheat protein," stated the researchers. "In cholesterol-binding experiments, 83 per cent of the cholesterol was associated with an insoluble buckwheat protein fraction, indicating strong cholesterol-binding capacity that disrupts solubility and uptake by Caco-2 cells."
"Considering that the gut contains such a large pool of cholesterol, dietary interventions like buckwheat protein may be effective in altering cholesterol levels," said Metzger.
The research is said to be ongoing with evaluation of how manufacturing processes might affect the content of buckwheat protein in the seed flour and how the buckwheat protein content might be enriched with current available protein production methods.
Source: Journal of Agricultural and Food Chemistry
Published on-line, ASAP Article, doi: 10.1021/jf0709496 S0021-8561(07)00949-1
"Insoluble Fraction of Buckwheat (Fagopyrum esculentum Moench) Protein Possessing Cholesterol-Binding Properties That Reduce Micelle Cholesterol Solubility and Uptake by Caco-2 Cells"
Authors: B.T. Metzger, D.M. Barnes, and J.D. Reed