Ultrafiltered milk, also known as UF milk, UF skim, or diafiltered milk, is a subclassification of milk protein concentrate that is produced by passing milk under pressure through a thin, porous membrane to separate the components of milk according to size. Specifically, ultrafiltration allows the smaller lactose, water, mineral, and vitamin molecules to pass through the membrane, while the larger protein and fat molecules are retained and concentrated. The removal of water and lactose reduces the volume of milk, and thereby lowers its transportation and storage costs. Ultrafiltered milk is used in cheese manufacturing to make the process more efficient. Ultrafiltered milk is also sold directly to consumers under brands like Fairlife and Simply Smart, who tout its higher protein content, lower sugar content, and creamier taste. The process of creating ultrafiltered milk involves passing skim milk through one or more membranes to filter out about half of the milks water content along with about half of the lactose, or milk sugar, while letting the milk protein molecules through. What youre left with is essentially concentrated milk—all the protein, plus half the water and half the lactose. Ultrafiltered milk is higher in protein and lower in sugar compared to regular milk, and it is lactose-free. It is appealing to a wide range of people, including fitness enthusiasts who like the extra protein, people who are lactose intolerant, and those that need to limit their sugar intake, such as diabetics.