Gutbliss - Dr. Robynne Chutkan

Lactose Intolerance


Lactose intolerance is a food intolerance where the small intestine doesn’t make enough of the enzyme lactase necessary for digesting the lactose sugar in milk. More than half the world’s population has some degree of lactose intolerance. Gas and bloating are classic symptoms of lactose intolerance, but it can be tricky to diagnose because the symptoms overlap with so many other conditions, including irritable bowel syndrome (IBS), celiac disease, H. pylori infection, SIBO, and gallbladder dysfunction.


Symptoms of lactose intolerance include:

  • Gas
  • Bloating
  • Loose stool or diarrhea
  • Constipation
  • Abdominal pain
  • Nausea
  • Foul-smelling stool

Lactose intolerance is recognized as a potential cause of irritable bowel syndrome, and it is sometimes confused with a poorly functioning gallbladder, as it can mimic similar signs and symptoms such as nausea, bloating, and abdominal pain.


There are three types of lactose intolerance: primary, secondary, and congenital.

Primary lactose intolerance occurs naturally with age. As we grow older, we become less reliant on milk and our bodies become less accustomed to processing milk. Therefore, lactose intolerance can sometimes arise.

Secondary lactose intolerance occurs because of injury or disease. Celiac disease and Crohn’s both affect the lining of the small intestine and can cause secondary lactose intolerance. Gastrointestinal infections like Giardia and Rotavirus are also common causes of lactose intolerance, which can be temporary or permanent.

Congenital lactose intolerance, although rare, is a genetic condition in which infants are born without lactase and must rely on lactose-free formula for survival.


If you think you might have lactose intolerance, the first step is an avoidance trial; avoid all dairy for a minimum of two weeks to see if symptoms improve. A lactose hydrogen breath test (see below) is a more formal way of diagnosing lactose intolerance, but it’s more cumbersome than simply assessing a patient’s symptoms after a couple of weeks of avoidance. If you think you may be lactose intolerant but are not sure, try avoiding all dairy for a minimum of two weeks to see if your symptoms improve.

Breath and Blood Tests

You can also do more formal testing involving breath or blood tests:

  • Lactose hydrogen breath test: In someone who is lactose-intolerant, lactose passes undigested from the small intestine to the colon, where it undergoes fermentation by bacteria into hydrogen and other gases. A rise in the level of these gases detected during the breath test is considered evidence of lactase deficiency.
  • Blood test: a blood test that measures the amount of glucose in your blood after drinking a lactose solution is another way to check for lactose intolerance. Failure of your blood sugar to rise indicates your body isn’t adequately digesting and absorbing lactose.


Lactose Avoidance

Once the diagnosis of lactose intolerance is made, either by evaluating the effects of removing dairy from your diet or with a test, then eliminating dairy products is the best way to control your symptoms. Most people have varying degrees of lactose intolerance and can tolerate small amounts of dairy but will have symptoms with larger doses. If your symptoms are mild and you can’t live without some dairy, reintroduce small amounts of yogurt and hard cheeses, which contain less lactose than foods like ice cream and mozzarella. If you’re bloated, irrespective of whether you have lactose intolerance, you may find that eliminating or cutting back on your dairy intake improves your symptoms. And remember that there’s no compelling reason to consume dairy—you can acquire plenty of calcium from green leafy vegetables and fish, and weight-bearing exercise is a great way to prevent osteoporosis.


Probiotics containing strands of Streptococcus thermophiles, a bacterium found in fermented milk products like yogurt and kefir, and Bifidobacterium longum, one of the founding bacterium species in infants, can improve lactose intolerance and can help digest lactose in the intestines.

Lactase supplements

Using lactase supplements or products with added lactase on a regular basis is not recommended, because if your body can’t digest something, avoidance rather than repeated exposure seems like the more sensible approach.

More than half the world’s population has some degree of lactose intolerance.


Dr Robynne Chutkan
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