Interesterified fats: What are they and why are they used? A briefing report from the Roundtable on Interesterified Fats in Foods

Interesterification rearranges the position of fatty acids within triacylglycerols, the main component of dietary fat, altering physical properties such as the melting point and providing suitable functionality for use in a range of food applications. Interesterified (IE) fats are one of a number of alternatives which have been adopted to reformulate products to remove fats containing trans fatty acids generated during partial hydrogenation, which are known to be detrimental to cardiovascular health. The use of IE fats can also reduce the saturated fatty acid (SFA) content of the final product (e.g. up to 20% in spreads), while maintaining suitable physical properties (e.g. melt profile). A novel analysis was presented during the roundtable which combined data from the UK National Diet and Nutrition Survey (2012/2013–2013/2014) with expert industry knowledge of the IE fats typically used in food products, to provide the first known estimate of population intakes of IE fats among UK children and adults. IE fats were found to contribute approximately 1% of daily energy across all ages. The major contributors to overall IE fat intakes were fat spreads (~54%) and bakery products (~22%), as well as biscuits (~8%), dairy cream alternatives (~6%) and confectionery (~6%). Increasing use of IE fats could contribute towards reducing total SFA intakes in the population, but would depend on which food products were reformulated and their frequency of consumption among sub-groups of the population. Studies comparing the effect of IE and non-IE fats on markers of lipid metabolism have not shown any consistent differences, either in the fasted or in the postprandial state, suggesting a neutral effect of IE fats on cardiovascular disease risk. However, these studies did not use the type of IE fats present in the food supply. This issue has been addressed in two studies by King's College London, which measured the postprandial response to a commercially relevant palm stearin/palm kernel (80:20) IE ‘hard stock’, although again no consistent effects of the IE fat on markers of lipid metabolism were found. Another study is currently investigating the same IE hard stock, consumed as a fat spread (blended with vegetable oil), and will measure a broader range of postprandial cardiometabolic risk factors. However, further long-term trials using commercially relevant IE fats are needed. Subsequent to the roundtable, a consumer survey of UK adults (n = 2062; aged 18+ years) suggested that there is confusion about the health effects of dietary fats/fatty acids, including trans fats and partially hydrogenated fats. This may indicate that providing evidence-based information to the public on dietary fats and health could be helpful, including the reformulation efforts of food producers and retailers to improve the fatty acid profile of some commonly consumed foods.