Pectin from both apple pomace and citrus could reduce LDL cholesterol by between 7 and 10% when consumed at a level of 15 grams per day for four weeks, but these results were only observed for pectin with a structure that included numerous methanol groups in its structure: High methoxyl (HM) pectin or pectin with a high degree of esterification.
“Based on the present work it appears that such [cholesterol-lowering] effects depend on the ability of the pectin type used, to induce a viscous gastro-intestinal content, which, in turn, is shown to depend strongly on the specific molecular composition, notably [degree of esterification] and [molecular weight],” wrote researchers from Maastricht University and Cargill R&D. The study was funded by Cargill European R&D Center.
“Generic claims for all pectin types to reduce cholesterol cannot be supported based on our data, and molecular characterization of pectin and dose should be considered for health claims.”
The chemical structure of pectin is based on a chain of repeating galacturonic acid units. In very basic terms, galacturonic acid has a ring structure with a carboxyl (CO2-) group jutting out. In nature, a large portion of these carboxyl groups have methanol (CH3OH) bonded via a reaction called esterification.
A high degree of esterification, or many bonded methanol groups, produces a high methoxyl (HM) pectin, while a low degree of esterification gives a low methoxyl (LM) pectin.
The ratio of esterified to non-esterified galacturonic acid units plays a central role in determining the properties and behaviour of the pectin, and determines which food applications it can be used in.
According to the results of the new study published in the European Journal of Clinical Nutrition, the degree of esterification also influences the pectin’s ability to lower LDL cholesterol.
Indeed, the European Food Safety Authority’s (EFSA) Panel on Dietetic Products, Nutrition and Allergies issued a positive health claim opinions for pectin for cholesterol lowering and effects on glycemia.
For maintaining normal blood cholesterol concentrations, EFSA considered that a cause-and-effect relationship has been established with 6 grams of pectin consumed in at least one serving.
The new study notes that the EFSA opinion does not go far enough and should “require a minimum level of characterization”.
The researchers recruited 30 men and women with mildly elevated cholesterol levels and assigned them to receive either 15 grams per day of pectin or cellulose for four weeks. Seven different types of pectin were used in the study: Citrus pectin with degrees of esterification of 0, 35 and 70, apple pectin with degrees of esterification of 35 and 70, orange pulp fiber with a degree of esterification of 70, and one pectin with a low molecular weight.
Results showed that both the citrus and apple pectin with the degrees of esterification of 70 performed equally well at reducing LDL cholesterol levels by 7-10%, while both types of pectin with degrees of esterification of 35 were the next best performers. The worst performer for cholesterol reduction was the citrus pectin with a degree of esterification of 0.
In a second study, volunteers were randomly assigned to receive six grams of citrus pectin with a degree of esterification of 70 or pectin with a high molecular weight and a degree of esterification of 70.
Results from this study indicated that consumption at a level “more realistic for daily inclusion in food” reduced cholesterol by 7-9%, compared with cellulose.
Implications for health claims
The researchers note that EFSA’s recently published health claim – ‘Consumption of pectin contributes to the maintenance of normal blood cholesterol levels’ – should also include information for the consumer that at least 6 grams of pectin per day is required to obtain these beneficial effects.
“In addition, EFSA (2010) concludes: ‘Consumption of pectin with meals contributes to the reduction of the blood glucose rise after those meals’. In order to bear this second claim, information should be given to the consumer that at least 10 g of pectin should be consumed per meal when wishing to control blood glucose levels,” they added.
Source: European Journal of Clinical Nutrition
Published online ahead of print, doi:10.1038/ejcn.2011.208
“Cholesterol-lowering properties of different pectin types in mildly hyper-cholesterolemic men and women”
Authors: F. Brouns, E. Theuwissen, A. Adam, M. Bell, A. Berger, R.P. Mensink