Skim milk is made by physically separating and removing the fat content from whole dairy milk. Since fat removal also strips the milk of all its fat-soluble vitamins, skim milk must be fortified with vitamins A and D to make up for the loss of nutrition. For the general population, skim milk serves as an excellent nutritional substitute for whole milk. It is the more favorable choice if you are on a reduced fat diet or have a higher risk of heart disease. However, there are experts who question the safety of the skimming process and argue that drinking skim milk instead of whole milk can result in adverse health effects.