If you're one of the many adults who can't consume dairy products because you struggle with lactose intolerance, you can consume lactose-free milk and dairy without difficulty. Dairy manufacturers can make lactose-free versions of milk and other dairy products by chemically reacting the lactose in milk, which removes the source of dietary difficulty and allows you to enjoy dairy-based foods.
If you're lactose intolerant, you're not allergic to milk — or even to lactose. Instead, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry," you lack the digestive enzyme you need to break down lactose, or milk sugar. This means lactose passes undigested into your lower gastrointestinal tract, where you harbor native populations of bacteria. The bacteria digest the lactose, producing gas as a byproduct, which leads to the painful cramping and bloating you feel when you consume milk.
It's neither practical nor really possible to remove lactose from milk — not only would it be logistically difficult, it's simply not necessary. Instead, manufacturers react the lactose chemically, altering its composition and converting it into molecules that your digestive system processes easily. To react lactose, manufacturers add small amounts of the enzyme lactase to milk, explains OrganicMeadow.com, a producer of lactose-free milk. The lactase splits lactose into its constituent components, which are two sugars called glucose and galactose.
Digesting Lactose-Free Milk
If you consume lactose-free milk, because the lactose has already been digested into glucose and galactose, you don't need to be able to produce the lactase enzyme to digest the milk. Instead, your intestinal tract can absorb the smaller sugars directly into the bloodstream, preventing intestinal symptoms associated with lactose intolerance. As such, lactose-free milk and other lactose-free dairy products cause no symptoms in lactose intolerant individuals.
One of the differences between lactose-free milk and regular milk and dairy is that the lactose-free variety will taste a bit sweeter. This is because lactose doesn't bind very tightly to sweetness receptors on the tongue, but its constituent sugars glucose and galactose do. The reason for this has to do with the shape of the lactose molecule, compared to the shapes of the glucose and galactose molecules, explain Garrett and Grisham.
While milk and some dairy products must be treated with lactase enzyme to render them lactose-free, other dairy products are lactose-free or nearly lactose-free without additional processing. For instance, most lactose-intolerant individuals can safely eat yogurt, because bacteria in the yogurt "pre-digest" the lactase. As a result, it's not necessary for manufacturers to make yogurt with lactose-free milk for the end product to be almost completely lactose-free.