Gut-related metabolic effects of lipid emulsions and emulsifiers

Abstract: The metabolic impact of dietary lipids needs to be considered beyond their fatty acid profile and energy value. Fatty acids are the building blocks of the different lipid molecules, including triacylglycerols, phospholipids and other polar lipids, which are organized within various supramolecular structures, either natural or formulated, such as lipid droplets. We will first highlight how emulsified structures and the food matrix can modulate postprandial lipemia and lipid metabolism. Moreover, even if more than 95% of dietary fatty acids are absorbed by the intestine to reach the bloodstream within the chylomicrons, thereby providing various fatty acids and lipids for metabolism, a small unabsorbed proportion is however able to interact with the microbiota and the cells of the distal intestine. Now, gut health including its barrier function and microbiota is now recognized as a major player in cardiometabolic health, which may be altered by some synthetic food additives as higlighted by recent research. Considering the growing need for sustainable and clean label ingredients, functional lipids can offer an advantageous alternative to synthetic emulsifiers. In this context, we will review recent findings on the impacts of polar lipids such as lecithins, on lipid metabolism and inflammation. We will highlight underlying mechanisms related to intestinal lipid absorption and to the metabolic fate of specific polar lipid residues in the distal intestine, the microbiota and some actors of the intestinal barrier. Considering dietary polar lipids, either as functional food ingredients or in native food matrixes, can thereby open perspectives in the nutritional management of metabolic disorders.