Lactose intolerance is the inability to digest lactose, the sugar in milk. Lactose is comprised of two sugar molecules: glucose and galactose. Lactose intolerant individuals have low activity of the enzyme lactase, which breaks down lactose into glucose and galactose. Lactose intolerance can also result from celiac disease, Crohn’s disease or infectious enteritis (1).

Lactose intolerance occurs in 65% of the world’s population. It is most prevalent in those of East Asian descent, as well as people of Jewish, Arab, Greek, Italian and West African descent. Only 5% of those with Northern European descent are lactose intolerant, due to a long history of dependency on unfermented milk products as a food source (2).

There are many signs and symptoms present with lactose intolerance. These symptoms can appear within 30 minutes to two hours after consuming dairy or dairy products (3). The severity of the symptoms typically depends on the degree of deficiency of lactase, the enzyme needed to digest lactose (4). In addition, there is variability among individuals regarding the symptoms experienced.

The more we become in touch with our bodies by listening to what they are telling us through various signs and symptoms, the greater our overall health and wellbeing.


Abdominal Pain
Muscle/Joint Pain
Mouth Ulcers

Some studies show that diarrhoea is the most common symptom of lactose-intolerance (4). Diarrhoea resulting from food intolerances may be osmotic diarrhoea. This kind of diarrhoea occurs because undigested lactose acidifies the colon, increasing the osmotic load (1). These solutes become retained in the intestine, causing water to be malabsorbed and resulting in diarrhoea.

Not all who are lactose intolerant experience diarrhoea. Some people also experience constipation, which may be due to decreased intestinal motility (1). This decreased motility could be caused by the production of methane, which is a result of the undigested lactose in the intestine (1). Along with constipation and diarrhoea, a person could experience painful bowel movements.

In the colon, bacteria ferment the undigested lactose. This fermentation process in the large intestine produces short-chain fatty acids, hydrogen, carbon dioxide and methane (1). The release of these gases by bacteria can cause intestinal distention and discomfort, creating bloating and abdominal pain as well as flatulence. Lactose intolerant individuals tend to produce gas that is distinctly odorous.

Those who are very intolerant to lactose may feel quite nauseous upon digesting lactose. These individuals may feel the urge to vomit. A person with this uncomfortable symptoms may need to expel the food immediately, or they may be able to wait for the nausea to pass in time. Vomiting could be another sign of lactose intolerance.

Headaches and migraines are often linked with food allergies and intolerances. In a study of 76 children who experience migraines, it was found that 39% of the cases were provoked by the addition of cow’s milk into the diet (5). These children also had related food intolerance symptoms of abdominal pain and nausea.


Not all the symptoms stemming from lactose-intolerance are digestive. Individuals who are lactose-intolerant can experience a wide range of symptoms, including neurological symptoms. Headaches and even migraines can be due to lactose-intolerance. Fatigue is another common sign of any kind of food sensitivity or allergy. Mouth sores, muscle and joint pains are other symptoms that are frequently experienced by those with lactose-intolerance.


Digestive enzymes can assist individuals with the reduction of these symptoms via the increased ability to digest lactose. When lactose is digested properly, then it does not enter the large intestine where symptoms of gas, bloating and abdominal pain occur. Digestive enzymes can be consumed with any meal where dairy is to be consumed.


1. Mattar, R., Mazo, D., Carrilho, F. (2012). Lactose intolerance: Diagnosis, genetic and clinical factors. Clinical and Experimental Gastroenterology; 5:113-121. doi: 10.2147/CEG.S32368

2. NIH, Lactose Intolerance. (2017, April). National Institute of Health. US Department of Health and Human Sciences. Retrieved from

3. NIH, Lactose Intolerance. (2014, June). National Institute of Health. National Institute of Diabetes and Digestive and Kidney Disease. Retrieved from

4. Saha, M., Parveen, I., Shil, B., et al. (2016, July). Lactose Intolerance and Symptom Pattern of Lactose Intolerance among Healthy Volunteers. Euroasian Journal of Hepto-Gastroenterology; 6(1): 5-7. doi: 10.5005/jp-journals-10018-1156

5. Egger J, Soothill, J.F., Carter, C.M., et al. (1983). Is migraine food allergy? A double-blind placebo-controlled trial of oligoantigenic diet treatment. Lancet; 2: 865-869


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