Niacinamide boosts barrier lipids and lowers water loss (2000)

This is mostly a laboratory study. In cultured human skin cells, niacinamide increased production of ceramides several-fold, along with other fats that make up the skin barrier. A smaller part of the study applied it to real skin and found more barrier lipids and less water lost through the surface. Laboratory results do not automatically translate to visible benefit, so read this as the mechanism behind niacinamide's barrier claims rather than proof of how well it works. The authors worked for a cosmetics manufacturer.