Does Dairy Tolerance Change Throughout Life?

Up to 75% of the world’s population experiences some form of lactose intolerance. But how does this happen considering everyone relies on their mother’s milk (or formula alternative) to survive after birth? And what factors lead to lactose intolerance?

Lactose is the primary sugar found in dairy products. Lactose intolerance occurs when there is a lack of the enzyme responsible for breaking down the lactose sugar. The MCM6 gene regulates the body’s ability to produce of lactase. Individuals with a certain version of the MCM6 gene lose the ability to produce lactase as they age and are unable to fully digest lactose. This typically leads to cramps, bloating and diarrhea after consuming lactose- containing dairy foods.

There are three possible genotypes for the MCM6 gene (rs4988235)

  • Lactase persistent – A/A genotype
  • Likely lactose intolerant – A/G genotype
  • Lactose intolerant – G/G genotype

Lactose intolerance is most common in people of African, Asian, Hispanic and American Indian descent.

Other factors may also influence lactose tolerance. The lactase enzyme is found on the brush board of the intestinal lining, therefore, any condition that leads to injury of the digestive tract can reduce the production of lactase. This is referred to as secondary lactose intolerance, rather than hereditary. Some common reasons this can occur is:

  • Injury of the small intestines
  • Surgery within the small bowel
  • Intestinal infection such as parasites, small intestinal bacterial overgrowth (SIBO)
  • Celiac disease (check the Gluten Card in LMH)
  • Crohn’s disease

Eliminating or reducing dairy products or consuming lactase supplements helps to reduce symptoms of lactose intolerance. It is quite common for individuals to be eating dairy and be unaware of persistent symptoms from lactose intolerance. This is where testing comes in handy. LoveMyHealth tests for the MCM6 gene to see if you are able to produce lactase.


  By Dr. Robyn Murphy, ND
  Scientific Advisory Board Member