What this means is that extra soy protein must be consumed to provide the needed amount of amino acids, and excess amino acids are wasted through the kidneys. Lesser quantities of milk provide more of the needed amounts of amino acids than soy does. While milk proteins can cause allergies in a few people, so can soy proteins. Milk fat differs from soy fat in unsaturated fatty acids and cholesterol content, but low fat milk, like 1 percent milk, has little or none of that difference. In yogurt the lactose is converted to easily digested lactic acid.
Most cheeses have no lactose contents, because it's lost into the whey during cheese making.
In fact, with its lactose sweetener and protein fortifier, commercial dry whey is a widely used in bakery products. Soy products contain no lactose, but they are also deficient in the valuable minerals and vitamins that distinguish real milk, primarily the calcium content. Most of the soybean's mineral and vitamin content is lost during processing into imitation dairy products, though supplements are often added. In terms of agronomic efficiency, it is possible to produce more than 400 pounds of soy protein per acre compared to maybe only one-third in milk protein. And don't underestimate the sociological value of milk production to the economic health of an entire country.