Lactose Intolerance – Why Most Adults Can’t Digest Milk

April 14, 2014


What is lactose intolerance?

Derived from glucose and galactose, lactose is a disaccharide sugar found in milk and most dairy products. Lactose is nutritionally beneficial because of its ability to generate energy through “slow hydrolysis”, improves mineral absorption and maintains healthy intestinal bacteria necessary for proper digestion. Lactose is added to infant formula because human milk contains lactose and contributes to infant health.

Lactose intolerance is not an allergy

Lactose intolerance is a genetic disorder that prevents humans from digesting lactose. Caused by a deficiency in lactase, an enzyme essential for breaking down and assimilating lactose, lactose intolerance is not an allergy but an immune system reaction to excessive amounts of milk protein in the body.

Individuals who are lactose intolerant may suffer mild to severe symptoms, depending on the amount of lactase in their bodies.

Different kinds of lactose intolerance

Three types of lactose intolerance exist: primary, acquired and congenital lactase deficiency. Primary lactase deficiency is genetic and affects more people than acquired or congenital lactose intolerance. Acquired lactase deficiency affects people suffering damage to the small intestine from acute diarrhea, gastroenteritis or parasitical infestation.

Congenital lactose intolerance is an extremely rare genetic disorder preventing expression of lactase from birth. Babies with this type of lactase deficiency cannot digest human milk.


Signs that you may be lactose intolerance

Symptoms of lactose intolerance include cramps, bloating, nausea, flatulence, diarrhea, a “rumbling” stomach and occasionally vomiting. Signs of lactose intolerance generally emerge within one hour of drinking milk or eating dairy products.

Symptom severity increases as more lactose is consumed. However, most people with lactase deficiency can tolerate a certain amount of lactose without suffering uncomfortable symptoms by limiting the amount of lactose consumed at one time.

Medical tests for lactose intolerance

Assessing lactose intolerance is based on a hydrogen breath and/or blood glucose test that determines the extent of lactase deficiency. People taking the hydrogen test are given 25 grams of water-diluted lactose to drink and later asked to breathe into a gas chromatograph device.

In the absence of enough lactase to break down lactose, intestinal bacteria metabolize lactose, producing hydrogen and methane gas. Detection of high levels of hydrogen and methane in a person’s breath means that they are probably lactose intolerant.

Cause of adult lactose intolerance

Adult lactose intolerance occurs because the gene responsible for producing lactase degrades as we age. Alternately, people who are genetically predisposed to maintaining “expression” of the lactose gene may only suffer very mild lactose intolerant symptoms or none at all as they enter their 40s.

However, because milk is rich in calcium and vitamin D (two nutrients needed by older people to prevent development of osteoporosis), people avoiding milk and dairy products due to cramping, nausea and other symptoms of lactose intolerance could suffer serious health issues such as reduced bone density and tooth loss.

Managing lactose intolerance

Mild to moderate lactose intolerance symptoms can be managed successfully by limiting milk intake to one glass per day (fat-free, whole and skim milk contain the same amount of lactose), eating cheddar or Swiss cheese (both have less lactose than other cheeses) and consuming reduced-lactose milk products. Over the counter drugs are also available that provide the body with extra lactase to help minimize symptoms.

Eating food with milk may reduce cramping and bloating. Periodically replacing milk with yogurt (which is rich in calcium) can also help people manage lactose intolerance symptoms because bacterial cultures found in yogurt actually produce the enzyme needed to break down lactose.