The type of fat used as a carrier for phytosterol in fortified foods and drinks could have a major impact on the ability of the ingredient to lower cholesterol, according to a new meta-analysis of trials.
Writing in Progress in Lipid Research, the Australian research team warn that the sort of fat used in functional spreads and dairy drinks that target lower cholesterol could have a major impact on the cholesterol-lowering potential of phytosterol.
Led by first author Jessica Ferguson from the nutraceuticals research group at the University of Newcastle in Australia, the team analysed data from more than 2,000 people pooled from 32 randomised controlled trials (RCTs) reporting on the effects of phytosterol (PS) on cholesterol.
“We report novel findings such that the carrier fat of common PS fortified foods does appear to modulate the cholesterol-lowering potential of PS,” said Ferguson and her colleagues, who added that the findings of this research provide industry with ‘useful evidence’ for optimising the cholesterol-lowering effects of PS-based functional foods.
While the findings of the study did show that all types of fat carrier tested resulted in lower measures of cholesterol in the RCTs, the team noted significant differences in exactly how much lower cholesterol was lowered.
“When compared across different carrier fats, rapeseed/canola (RC) as the main carrier fat, reduced LDL-C significantly more than the soybean/sunflower (SS) spreads,” they revealed.
Canola: The perfect carrier?
Ferguson and colleagues suggested that the combination of monounsaturated fatty acids, with adequate amounts of omega-3 fatty acids, as is evident in canola-based functional spreads “may be the superior carrier fat for the delivery of PS”.
Furthermore, the team noted that in addition to cholesterol-lowering potential of phytosterol fortified RC fat spreads, the health benefits of MUFA and omega-3PUFA, which are the predominant fats found in RC fat spreads, “support RC as an ideal carrier fat for PS, providing additional cardio-protective action to improve the lipid profile of atherogenic LDL-C by lowering its oxidation susceptibility,”
“The findings of this review suggest the importance of considering the fat composition used for PS fortified products in order to yield optimum cholesterol-lowering outcomes,” they said.
What about dairy?
The team noted that although dairy (D) products were analysed alongside SS and RC products, no significant differences between dairy and any of the other fat carriers were found.
“It is noteworthy that compared to the RC and SS groups, the D group contains a diverse range of products with differing fat content; including butter, cheese, yoghurt and low-fat milk,” they commented. “Moreover, compared to the SS and RC group, the D group is complex since the level of SFA varies greatly, making it less of a homogenous group to include in the comparison against RC and SS.”
As a result, Ferguson and colleagues reported that this greater heterogeneity due to varying fat content in the D group resulted in a larger confidence interval and consequently the difference did not reach a significant level compared to SS or RC groups.
Ferguson et al also noted that many ‘dairy’ products used in such RCT studies contained added vegetable fats, often in amounts that override the typical fatty acid composition of a regular commercial low-fat milk based on cow's milk.
“Therefore, in this meta-analysis we have only included dairy fat-based product studies which have a nutritional profile representative of commercial dairy milks.”
They concluded that given the diversity of the RCTs pooled on dairy-based studies, “the role of dairy fat in modulating the cholesterol-lowering effects of PS cannot be clearly established in the present analysis.”