lactose intolerance milk pouring into glass

Most of us are pretty aware of the term lactose intolerance as many of us probably struggle with the condition to some extent!

Lactose, a disaccharide sugar composed of one glucose molecule and one galactose molecule, is found in most dairy products. A lactose intolerance occurs when one experiences an adverse response such as bloating, gas, abdominal pain, cramping and diarrhea within minutes to hours after consuming lactose.

The intensity of the symptoms experienced correlates to the amount of lactose consumed as well as the degree of intolerance of the individual. This all seems pretty straightforward, right? Well, this article will divulge 6 things you don’t already know about lactose intolerance. 

  1. The lactase enzyme differs in age and ethnicity:

    • As we age, lactase production naturally declines, which results in primary adult-onset lactase deficiency. In most populations, this occurs after the age of 2. 
    • Certain ethnic groups are more likely to experience lactose intolerance including Asians, Africans, Native Americans and those of Middle Eastern, Arctic or Mediterranean descent.
    • Those from Scandinavia and Great Britain experience the least amount of lactose intolerance at a rate of ~3-15% of their population. Those with high levels of lactase often co-evolved with dairy and have a single nucleotide polymorphism (SNP) of the rs49882359 allele (C/T) that helps positively influence lactase production. 
  2. Babies digest lactose like a pro:

    • Human breast milk contains more lactose than cow’s milk at a rate of 6% compared to 4%. 
    • The majority of all human babies have the ability to adequately digest lactose except those diagnosed with a rare medical condition called congenital alactasia. This is an autosomal recessive disorder that is typically identified within the first 10 days of life. 
    • While lactose intolerance in infants is rare, they may still experience poor tolerance to milk to due a milk allergy. Symptoms may appear similar, but it is vital to have an accurate diagnosis in order to follow through with appropriate dietary changes. 
  3. Damage to the digestive tract can cause temporary lactose intolerance:

    • The lactase enzyme is produced in the brush border cells of the digestive lining. Anything that causes inflammation and damage to the lining can temporarily reduce the production of lactase and result in a secondary lactase deficiency
    • Damage to the gut lining may be caused by:
      • Rotavirus, Giardia, Cryptosporidium, Blastocystis, and other bacterial or viral infections
      • Celiac disease
      • Inflammatory bowel disease (IBD)
      • Antibiotics 
      • Trauma or surgery of the digestive tract 
  4. Lactose intolerance doesn’t just involve the colon: 

    • Lactose sugar is an osmotically-active molecule that cannot permeate the membrane of the digestive tract unless it is broken down into smaller particles. When undigested lactose enters the colon, it changes the osmotic pressure of the environment. Microbes in the colon ferment the lactose and produce gas, organic acids, and other by-products, which results in digestive symptoms.
    • The experience of lactose intolerance is also dependent upon the person’s sensitivity to pain, gastric emptying rate, gastrointestinal motility, and the type of microbes inhabiting the colon.
  5. You may actually have lactose malabsorption:

    • Lactose intolerance indicates the presence of digestive symptoms associated with consuming a certain lactose-load. Lactose malabsorption refers to lactose not breaking down or absorbing, but this may or may not produce digestive symptoms. Most people have both conditions!
    • One may be lacking in the lactase enzyme, but still tolerate lactose due to the specific microbial environment in their gut. 
    • Diagnosing lactose malabsorption involves genetic testing, endoscopy, and H2-breath tests
  6. You cannot change your body’s ability to produce lactase:

    • Unfortunately, our ability to produce lactase is mostly related to our genetics. Consuming foods that contain lactose or not will not change your ability to produce lactase.
    • However, foods that contain lactose provide the body with specific types of bacteria that colonize the colon. These microbes are able to synthesize an enzyme called beta-galactosidase that helps to break down lactose in the colon.
    • Additionally, undigested lactose increases the fermentation of certain bacterial strains that also help to metabolize lactose.  This helps improve osmotic balance in the colon and therefore the distress of lactose intolerance.

Okay, now you are officially the lactose intolerance pro! I’ll leave you with a few of my top considerations for those who have lactose intolerance.


  • Use lactase enzymes as a supplement prior to the occasional intake of lactose-containing dairy
  • Consume hard cheeses made from the curd to avoid lactose, which is found in the liquid-whey portion of milk
  • Use butter without worry as it does not contain lactose
  • Whey protein isolate is lactose free, but whey protein concentrate is not 
  • Try fermented milk or milk products (yogurt or kefir) because they naturally help your body to break down lactose
  • Most people with lactose intolerance tolerate 12-15 grams of lactose so there is no need to completely avoid dairy
  • Consider including various non-dairy sources of calcium if you tend to limit your dairy intake:
    • These foods contain >200mg of calcium-
      • 1c cooked collards, 1c cooked rhubarb, 3oz sardines with bones, 1c edamame, 1c cooked spinach, 1/2c firm tofu, 1c raw oysters, 3oz salmon with bones, 1c cooked turnip greens
    • The amount of calcium absorbed and retained by the body varies based on age, food type, and other nutrients consumed simultaneously.
      • Most absorb ~40% of calcium consumed and this level increases during periods of growth, pregnancy and lactation.
      • Vitamin D helps with the absorption of calcium whereas as high protein and phosphorus diet will reduce calcium retention. 

To learn more or to get additional help with topics related to lactose intolerance or digestive concerns, contact me to today to set up an appointment! 


The Health Professional’s Guide to Food Allergies and Intolerances by Janice Vickerstaff Joneja, PhD, RD, 2013