The enzyme lactase is necessary for the digestion of milk and milk products. While most people naturally produce lactase as infants, the ability to do so declines with age for many people, especially those from populations where milk was not traditionally consumed. Lactase produced in the lab is a viable option for those who choose to consume dairy but have lost their own ability to produce the enzyme.
Purpose
Newborn babies need lactase in order to break down the lactose in breast milk and convert it into glucose and galactose, which can be used as fuel. Formula-fed babies also utilize this enzyme when digesting cow's-milk-based formulas. As a child gets older and weans, the absolute need for lactase declines. In populations where dairy was traditionally a major food source, such as in northern Europe and some areas of India, mutations developed to maintain lactase production into adulthood.
Biology
Lactase is produced by the gene LCT, which operates in cells lining the small intestines that are called intestinal epithelial cells. These intestinal epithelial cells use the lactase they produce to break down lactose into two other sugars, glucose and galactose. Another gene, called MCM6, regulates the expression of LCT. Most people in the world have the original form of the MCM6 gene and are therefore lactose intolerant. However, about 35 percent of people have a mutation that allows them to continue making lactase.
Supplemental Lactase
As the prevalence of milk and dairy products grows, many people who cannot produce enough lactase turn to supplemental forms of the enzyme to help them tolerate these foods. Supplemental lactase can be produced using yeasts, such as Kluyveromyces lactis, or fungi, such as Aspergillus niger. Commercially produced lactase is sometimes added to milk before packaging in order to make it lactose-free. Supplemental lactase is also sold in tablet and liquid form, which are taken before consuming products containing lactose.
Special Considerations
While sometimes referred to as a lactase deficiency, lactose intolerance is the normal state for most people in the world. Most people with lactose intolerance do produce some lactase, just not enough to completely digest lactose. However, some babies inherit a rare disorder that causes a complete inability to make lactase. The use of lactase to digest lactose in expressed breast milk or formulas in order to create lactose-free versions may be a lifesaving intervention for these infants.
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