There are four major dietary carbohydrates: lactose, fructose, sucrose, and starch. Lactose is the sugar found in breast milk. An enzyme called Lactase, which is found in the lining of the small intestinal wall, is responsible for breaking down lactose into its smaller subunits (glucose and galactose) for absorption through the intestinal wall into the blood vessels. Lactase deficiency leads to improper digestion of lactose, which is a condition called lactose intolerance. The undigested lactose travels down from the small intestine into the colon, dragging with it massive amounts of water through a process called osmosis, which could lead to watery diarrhea. The undigested lactose finally gets metabolized by the bacteria in the colon, resulting in fermentation, which produces a copious amount of gas such as hydrogen gas, carbon dioxide gas, and the foul-smelling methane gas. The graphic below shows this pathway.
It is important to distinguish between lactose intolerance and dairy sensitivity. Dairy sensitivity is an allergic reaction to the proteins found in dairy and leads to eczema, sinus problems, allergic reactions of the gastrointestinal lining, worsening of inflammatory bowel disease, and other allergic conditions.
Lactase deficiency (lactose intolerance) in adults is the most prevalent genetic deficiency syndrome worldwide and affects more than 60% of the population. Lactase activity decreases precipitously after age 5 and leads to lactose intolerance. Lactose intolerance could also occur after intestinal infections or inflammatory conditions such as rotavirus infection, Crohn’s disease, celiac disease, radiation therapy, a giardia infection, and other medical issues.
Signs and symptoms of lactose intolerance:
Lactose intolerance leads to uncomfortable abdominal distention or bloating, cramping, pain, excessive flatulence, diarrhea, burping, and belching 30 minutes to 2 hours after ingesting dairy products. Some people even experience acid reflux, and in rare cases constipation.
Unfortunately, lactose intolerance is commonly misdiagnosed as Irritable Bowel Syndrome (IBS) due to under recognition of this common syndrome. Therefore, for those diagnosed with IBS, it would be worthwhile avoiding dairy for one month to reassess clinical symptoms.
Diagnosis and treatment of lactose intolerance:
The best way to diagnose lactose intolerance is by avoiding all dairy products for 30 days and assessing the body’s clinical response. During these 30 days, be sure to read labels carefully, as dairy products are hidden in many packaged foods.
If digestive symptoms decrease or disappear during these 30 days, but reoccur when you have reintroduced dairy into your diet, this is a positive sign that you may be lactose intolerant. To avoid these uncomfortable symptoms, eliminate dairy from your diet moving forward.
If you think you or someone you know may be lactose intolerant but are not entirely sure, take our Lactose Intolerant Quiz!
Emily finally saw athletic results when she gave up dairy as a college athlete.
Spoiler alert: chocolate milk is not a recovery food.
Ultramarathoner Mandy Gill dishes on her favorite dairy-free brands.