The Facts on Lactose and Milk Sugar

Milk in a glass
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Also referred to as “milk sugar,” lactose is the disaccharide component in milk, composed of the monosaccharide components glucose and galactose. In order to digest lactose, a naturally-occurring enzyme, lactase, is required. While humans are born nautrally able to produce ample amounts of lactase in order to digest lactose products while nursing, lactase production generally decreases with age, resulting in lactose intolerance.

While lactose occurs naturally in dairy products such as milk, cheese, and yogurt, it is also frequently present in processed foods as well.

How Lactose is Digested

When lactose is digested, the small intestine, which is responsible for nutrient absorption, produces an enzyme that helps break down lactose called lactase. The result of the lactase enzyme is simpler forms of sugar: glucose and galactose. These simple sugars are easily absorbed into the bloodstream and used as energy. 

What Is Lactose Intolerance?

Lactose intolerance occurs when people don't produce enough lactase or do not digest lactose well. Lactose intolerance is not a milk allergy, which is a different condition that starts in infanthood and affects between 2 and 7% of children. People with lactose intolerance don't have to avoid dairy altogether and may be able to eat small amounts of lactose depending on their sensitivity to lactose.


For those who are lactose intolerant, there are a few options to control the symptoms of lactose intolerance. There are lactose-free and lactose-reduced milk products at most grocery stores. They are almost identical nutritionally to regular milk products. The products are made by milk manufacturers who treat regular milk with the lactase enzyme to break down the lactose.

A noticeable difference between regular and lactose-free milk is that it tastes slightly sweeter than regular milk. In terms of storage and shelf-life, lactose-free milk will keep the same amount of time as regular milk. 

Lactase products offer people another way to manage their lactose intake. By taking tablets or drops when eating or drinking dairy items, lactose is digested better without the discomfort of lactose intolerance symptoms. 

Symptoms of Lactose Intolerance?

Symptoms of lactose intolerance usually occur within 30 minutes to 2 hours after eating dairy products. Symptoms can be mild or severe but are not life-threatening. Symptoms usually include bloating, an uncomfortable feeling of fullness, as well as cramping and abdominal pain, diarrhea, gas, and nausea.

How Is lactose intolerance diagnosed?

A health care provider makes a diagnosis of lactose intolerance based on the person's family history, dietary history and prevalence of symptoms soon after meals. Another way to confirm lactose intolerance is by physical exam and other medical tests.