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Health Information | 10/31/2017

Do You Suffer From Lactose Intolerance?

By  Dr. Lily Wong
lactose intolerance

According to the National Institute for Health (NIH), approximately 65% of the human population has a reduced ability to digest lactose after infancy. Lactose is a natural sugar commonly found in milk and dairy products. Lactase is an enzyme found in the small intestines which breaks lactose down into more simple sugars to be absorbed into the body.  When there is a deficiency in lactase, undigested lactose in the intestines pulls in water and gets fermented by bacteria which results in gas production. This increase in fluid and gas in the bowels is what creates symptoms of abdominal pain and bloating.


Lactose malabsorption is usually due to an acquired deficiency in lactase that starts in early childhood, around the time we start weaning from milk products. As you age, lactase levels begin to decline. Therefore, the older you get the more at risk you are to develop lactose intolerance. Some racial and ethnic groups such as Asians, African Americans, Native American Indians, and Hispanics have been reported to have a higher incidence of lactose intolerance. Lactose malabsorption can also develop as a result of diseases that affect the lining of the small intestines and interfere with lactose digestion. Examples of such small bowel conditions include celiac disease, bacterial overgrowth, infection, or inflammatory bowel disease such as Crohn’s disease. In some rare cases, lactase deficiency can occur at birth due to a gene mutation that causes an absence of lactase or as a result of reduced lactase activity associated with premature birth.


Symptoms usually begin 30 minutes to 2 hours after eating foods that contain lactose and may vary significantly depending on the extent of lactase deficiency, the individual’s sensitivity to symptoms, and the amount of time it takes for food to travel through the body. The amount of lactose in 8 to 12 ounces of milk is usually sufficient to produce symptoms. The most common symptoms include stomach bloating, excessive gas, and crampy abdominal pain. Children and adolescents may vomit or have diarrhea.

How is it diagnosed?

A diagnosis can usually be made based on the symptoms you experience after consuming dairy products. If you eliminate dairy from your diet and your symptoms subside, this can help to further validate a diagnosis. There are tests that can be performed in your doctor’s office. The lactose breath hydrogen test is based on the premise that bacterial fermentation of lactose produces hydrogen and other gases. During this test the hydrogen levels in your breath are measured over a period of a couple hours. Another option is the lactose tolerance test where your blood sugar levels are measured for several hours after you eat or drink lactose.


Since there is a variability in the degree of intolerance, complete avoidance of lactose is often times not necessary. For some, limiting milk intake to less than 8 ounces a day may be enough to reduce symptoms. Symptoms can also be eased by eating small amounts of lactose along with other foods which helps to slow down the digestive process. Ice cream, milkshakes and aged hard cheeses are usually better tolerated than milk because of their higher fat content. Soy milk, rice milk and yogurts with live or active cultures usually do not cause symptoms. Lactose-reduced milk and other dairy products are available at most grocery stores. There are also commercially prepared lactase enzymes, such as Lactrase and Dairyease, that you can take with a lactose containing meal to help ease symptoms in those with mild intolerance.

Since dairy products provide a major source of calcium in our diet, it is important to ensure you get an adequate amount of calcium from other sources to maintain strong, healthy bones. For an adult, the recommended daily calcium intake is 1200 mg daily. Some non-dairy foods which are rich in calcium include sardines, shelled shrimp, artichokes, tofu, fresh broccoli, spinach, and orange juice. If you suspect you may have lactose intolerance you should consult your primary care provider to get a full assessment of your symptoms and rule out any other causes.

About The Author

Dr. Lily Wong

Dr. Lily Wong is an internist at our Dedham practice and is board certified in internal medicine. She received her medical degree from the University of Massachusetts School of Medicine in Worcester and completed both her internship and residency at Tufts Medical Center in Boston.

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