Lab animals fed a cholesterol-raising diet benefited significantly from the combination of pea protein with oat fiber or apple pectin, compared to the ingredients on their own, according to findings published in the British Journal of Nutrition .
Both protein and soluble fiber have previously been linked to cholesterol improvements, and the new study deepens this understanding by showing that the interventions affect gene expression.
Cholesterol is broken down in the liver to replenish the bile acid pool, and this is controlled by an enzyme called CYP7A1, explained the Milan-based researchers. In their study, they observed a “significant increase of this enzyme […] in rats fed both oat fibers and apple pectin.
“A significant reduction in hepatic cholesterol content was observed with both soluble fibers, possibly as a consequence of reduced intestinal cholesterol absorption and increased bile acid synthesis,” they added.
High cholesterol levels, hypercholesterolemia, have a long association with many diseases, particularly cardiovascular disease (CVD), the cause of almost 50 per cent of deaths in Europe and the US.
A report from the American Heart Association predicted a tripling of direct medical costs of cardiovascular disease from $272.5 billion to $818.1 billion between 2010 and 2030 (Circulation, March 2011, Vol. 123, pp. 933-944).
The new study, led by Giulia Chiesa, indicates that the combination of pea protein and soluble fiber may help, and supports findings from a human study published last year in the same journal (Br J Nutr Vol. 107, pp. 1176–1183).
Chiesa and her co-workers divided lab rats into six equal groups of 12 animals each and fed them all a hypercholesterolaemic diet for 28 days. The groups were further supplemented with casein and cellulose (control group), pea proteins + cellulose, casein + oat fiber, casein + apple pectin, pea proteins + oat fibres, and pea proteins + apple pectin.
Results showed that all the vegetable-fed animals displayed lower total cholesterol concentrations compared with the control, with the combination groups showing the biggest reduction in cholesterol.
In addition to the changes in CYP7A1, the researchers also observed changes in expression of a protein called NTCP that is responsible for the uptake of bile acids in the liver.
“Pea proteins, apple pectin or oat fibers are dietary components extremely effective in reducing cholesterolaemia in rats,” they wrote.
“The combination of these ingredients in the diet results in an additional efficacy with respect to soluble fibers alone, mainly consequent to reduced cholesterol and bile acid absorption.”
Source: British Journal of Nutrition
Published online ahead of print, FirstView Article, doi: 10.1017/S0007114513000639
“Effect of the combinations between pea proteins and soluble fibres on cholesterolaemia and cholesterol metabolism in rats”
Authors: C. Parolini, S. Manzini, M. Busnelli, E. Rigamonti, M. Marchesi, E. Diani, C.R. Sirtori, G. Chiesa