When fat molecules come into contact with digestive enzymes, the fatty acids at the sn-1 (alpha) and sn-3 (gamma) position are detached and ‘freed’, while most ones at the sn-2 (beta) position stay connected to the glycerol backbone. Now, the fat energy can be absorbed into the bloodstream. But as this is happening, the ‘free’ fatty acids can also start binding with other compounds.

The saturated fatty acid palmitic acid has the particular tendency to clump together with calcium, forming an insoluble ‘soap’. When this happens, neither the fat nor the calcium in the soap can be absorbed and they both end up being excreted in the stool. But when the palmitic acid stays connected to the glycerol backbone, it cannot bind with calcium. This is why the position of this saturated fatty acid on the molecule is so important – it can positively or negatively impact the infant’s energy and calcium supply, as well as the consistency of the stool.

Lipid digestion and fatty acid absorption pathways.