The exact components of milk vary by species, but it contains significant amounts of saturated fat, protein and calcium. These amounts are not large in comparison to other foods rich in them, including coconuts, fish, and kale respectively, because milk is predominantly composed of water. Aquatic mammals, such as seals and whales, produce milk that is very rich in fats and other solid nutrients when compared with land mammals' milk. Most milk packs a nutritional punch and contains protein, calcium, phosphorus, vitamins A and D, LACTOSE (milk sugar) and riboflavin. On the minus side, milk's natural sodium content is quite high. Most milk sold in the United States today is PASTEURIZED, which means the microorganisms that cause diseases (such as salmonella and hepatitis) and spoilage have been destroyed by heating, then quick-cooling, the milk. Pasteurization eliminates the possibility of disease and gives milk a longer shelf life. Most commercial milk products have also been HOMOGENIZED, meaning that the milk fat globules have been broken down mechanically until they are evenly and imperceptibly distributed throughout the milk. The end result is that the CREAM does not separate from the milk and the liquid is uniformly smooth. Cow's milk is generally available in several varieties. In some countries these are: Full cream (or "whole" in US, "homo milk" in Canada & some US dairies, about 3.25% fat) Semi-skimmed ("reduced fat" or "low fat", about 1.5-1.8% fat) Skimmed (about 0.1% fat) Milk in the U.S. and Canada is sold as: Whole varieties 2% (reduced fat) 1% (low fat) <0.5% (very low fat) Skim (nearly no fat) or fat free In the United States, skim milk is also known as "fat free" milk, due to USDA regulations stating that any food with less than Â½ gram of fat per serving can be labeled "fat free".