Young woman saying no to a glass of milk

Lactose Intolerance

Impacting more than 7 million Canadians understand more about this condition.

Lactose intolerance is a digestive, malabsorption disorder where one is unable to properly digest dairy products. Lactose is a carbohydrate found in dairy products (such as milk and cheese, for example) and is referred to as the sugar substance in dairy. This digestive disorder is ultimately caused by the inability to produce lactase, an enzyme that breaks down lactose and absorbs the carbohydrate. 

This can lead to lactose further processing through to the colon without enzymatic breakdown. In many instances, this inability to produce lactase can cause digestive issues such as diarrhea, nausea, vomiting, stomach cramps/pain, bloating or excessive gas.

What happens in my body if I’m lactose intolerant? 

Normally, when someone eats something that contains lactose, an enzyme that’s produced in your small intestine called lactase breaks down lactose into it’s simpler components (which are simple sugars called glucose and galactose). 

These simple sugars are then able to be absorbed in the bloodstream and give you the energy you need. If you have lactose intolerance, the body doesn’t make enough lactase to break down lactose, and as a result allows undigested lactose molecules to pass to the lower parts of the intestine. At this point, the undigested lactose encounter bacteria which begin digestion through a process of fermentation. The outcome of this fermentation (hydrogen, carbon dioxide, methane gases, and short-chain fatty acids) leads to many of the telltale symptoms for lactose intolerance –  like gassiness and diarrhea.

Prevalence

Lactose Intolerance is the most common food intolerance affecting roughly 44% of Canadians according to a 2016 census documented in the Journal of the Canadian Association of Gastroenterology (Fung et al, 2020). The Canadian population in 2016 was approximately 36 million people. This census revealed that roughly 16 million people in Canada had experienced some form of lactose malabsorption. Below are the average lactose intolerance rates for each region of Canada:

  • The Atlantic Provinces (Nova Scotia, New Brunswick, Prince Edward Island and Newfoundland and Labrador) – 26% of the population surveyed
  • Central Canada (Ontario and Quebec) – 43% of the population surveyed
  • Prairies (Saskatchewan, Manitoba and Alberta) – 46% of the population surveyed
  • The West Coast (British Columbia) – 52% of the population surveyed
  • The Northern Territories (Northwest Territories, Yukon and Nunavut – 55% of the population surveyed

Lactose Intolerance In Relation To Genetic And Cultural Aspects

In the scholarly article entitled “Country, regional, and global estimates for lactose malabsorption in adults: a systematic review and meta-analysis” written by Storhaug, Fosse and Fadnes, the authors conducted a meta-analysis of the prevalence of lactose malabsorption in adults across countries and regions. Their findings identified that lactose malabsorption is an issue which affects individuals throughout most of the world. Their comprehensive assessment revealed that around two-thirds of the world’s population suffers from lactose malabsorption.

This figure was derived from Storhaug’s, Fosse’s and Fadness’ article entitled ‘Country, regional, and global estimates for lactose malabsorption in adults: a systematic review and meta-analysis”.

Figure 1: Prevalence of lactose malabsorption in different countries assessed with all methods (Storhaug et al, 2017)

For clarity, countries shaded in cooler colours in Figure 1 above reflect populations with lower frequencies of lactose malabsorption. Those countries shaded in green to yellow reflect populations with medium frequencies of lactose malabsorption. Lastly, countries shaded in warmer orange and colours reflect the highest frequencies of lactose malabsorption.

Storhuag et al also discussed the issue of lactose malabsoption in Canada. They found large variations of rates of lactose malabsorption across different regions and provinces in the country (Storhaug et al, 2017). Based upon these findings, there does appear to be a link between Storhaug et al’s findings and the 2016 census conducted by Fung et al. The data taken as a whole appears to suggest that provinces in Canada which have populations that are made up of largely European descendants reflect lower rates of lactose malabsorption. For example, Fung et al’s 2016 census revealed that only 23% of Newfoundland and Labrador’s population suffers from lactose malabsorption – while its descendants are made up primarily of British and Irish descendants (Canadian Immigration Specialists, para. 4, n.d.). As we can see from Figure 2 noted above, populations in Britain and Ireland experience some of the lowest rates of lactose malabsorption, reaffirming the link between lactose malabsorption rates and descendant migration patterns.

With over 65% of the adult population experiencing lactose intolerance the treatment sometimes does not get the clinical attention that is necessary, because the symptoms and the development of the condition are driven by a variety of biological aspects that are unique to each individual.

Finding patterns in lactose malabsorption throughout diverse cultural groups and regions can lead to further treatment for populations who have high frequencies of the digestive disorder.


Students from the Culinary Management Nutrition Program at George Brown College Chef School participated in an academic writing content to create a lactose intolerance article for CDHF. The course, called Nutrition Issues, is taught by nutrition professor, Dr. Linda Gillis. Students highlighted the multicultural aspect of our nation and how lactose intolerance rates differ throughout Canada.  Their experience in planning meals using creative recipes is highlighted in this article.  Chante Grant and Mariana Schille were the winners for the contest.  George Brown College provides students with real world applications and opportunities for learning. Learn more more about Culinary Management Nutrition program.


References

Fung, M., Xue, X., Szilagyi, A. (2020). Estimating Lactase Nonpersistence Distributions in the Multi-Ethnic Canadian Demographic: A Population-Based Study, Journal of the Canadian Association of Gastroenterology, 3(3), 103-110. https://doi.org/10.1093/jcag/gwy068

Storhaug, C., Fosse, S., Fadnes, L. (2018). Country, regional, and global estimates for lactose malabsorption in adults: a systematic review and meta-analysis., The Lancet Gastroenterology & Hepatology, 2, 738-746. https://doi.org/10.1016/S2468-1253(17)30154-1

Canadian Immigration Specialists. (n.d.). The Atlantic Provinces of Canada. Canadian Immigration Specialists. https://brazolotmigration.com/resettling-in-canada/living-in-canada/the-atlantic-provinces

Familiar signs and symptoms include:

  • Diarrhea
  • Nausea
  • Vomiting
  • Stomach cramps/pain
  • Bloating
  • Excessive gas

It is crucial to mention that each person’s symptoms may differ. Symptoms can begin as early as 30 minutes after dairy is consumed or can be delayed up to 2 hours after consumption. It is important to be aware of these symptoms and triggers because the pain and discomfort could ultimately lead to a lower quality of life.

Below are common foods along with their associated lactose percentages:

Whole Milk13 grams, per 1 cup (Brennan, 2020)
Cheddar Cheese0.4 to 0.6 grams, per 1 ounce (UpToDate, n.d.)
Ice Cream2 to 6 grams, per ½ cup (UpToDate, n.d.)
0% Yogurt4 to 17 grams, per 1 cup (UpToDate, n.d.)
Chocolate Milk12 grams, per 1 cup (Gupta, 2019)

Why can some people who are lactose intolerant consume some lactose products?

It depends on how much of the lactase enzyme one individual can produce. Lactase is the enzyme that breaks down lactose and turns it into glucose and galactose so that it can be absorbed. If an individual was able to form a low amount of lactase in their small intestine, they would still be deemed lactose intolerant. However, they could still in theory properly process and break down certain dairy products that have low lactose amounts. (Mayo Clinic, n.d.)

In the early stage of life, infants can produce their own lactase, especially those who are being fed mammalian milk. As infants get older, the production of lactase declines, and the individual loses the ability to digest lactose. A person can develop issues with lactose and dairy digestion at any point of the life. People may not have problems with lactose during early stages of life but may experience the symptoms after going through a chemotherapy session, after the use of antibiotics, or any kind of digestive infection could be a trigger point or a cause for lactose malabsorption during older age.


Students from the Culinary Management Nutrition Program at George Brown College Chef School participated in an academic writing content to create a lactose intolerance article for CDHF. The course, called Nutrition Issues, is taught by nutrition professor, Dr. Linda Gillis. Students highlighted the multicultural aspect of our nation and how lactose intolerance rates differ throughout Canada.  Their experience in planning meals using creative recipes is highlighted in this article.  Chante Grant and Mariana Schille were the winners for the contest.  George Brown College provides students with real world applications and opportunities for learning. Learn more more about Culinary Management Nutrition program.


References:

Brennan, D. (2020, October). Foods High in Lactose. WedMD. https://www.webmd.com/diet/foods-high-in-lactose#:~:text=Whole%20milk%20contains%20about%2013,between%2012%20and%2013%20grams.

UpToDate. (n.d.). Lactose content of different foodsUpToDate https://www.uptodate.com/contents/image?imageKey=PI%2F55938

Gupta, S. (2019, October). Chocolate Milk Nutrition Information. Livestrong. https://www.livestrong.com/article/46306-chocolate-milk-nutrition-information/

Mayo Clinic. (n.d.). Lactose intolerance.https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232#:~:text=Too%20little%20of%20an%20enzyme,able%20to%20diges t%20milk%20products.

How to test for lactose intolerance?

The elimination diet – where an individual stops consuming dairy products – is often used as a method for identifying lactose intolerance. However, the main way of testing for lactose intolerance is through an assessment with a doctor. The assessment begins 2 hours after the patient consumes a large quantity of lactose (typically through a beverage form). The patient then has their blood tested to measure the amount of glucose found in their blood. If the glucose levels stay the exact same, even after an individual has consumed a considerable amount of lactose, this shows that the body is not properly absorbing the lactose. This result typically ends in a diagnosis of lactose intolerance.

Lactose Intolerant Treatments and Dietary Alternatives

A person who is lactose intolerant should generally avoid consuming dairy products. There are certain types of dairy products that can be enjoyed by one who is lactose intolerant. For example, hard cheeses, such as Parmesan or Swiss, can often be enjoyed without symptoms because these cheeses have a very low lactose content (Mikstas, 2020). The intensity of the symptoms and the prevalence of it will vary depending on the amount of lactose being ingested. Studies have shown that some people have a tolerance to one cup of milk per day (12- 19g of lactose) without symptoms. (Storhaug, Fosse, Fadnes, 2017). Those who experience extreme lactose intolerance should keep to a strict ‘no dairy diet’.

However, milk and dairy products, are hidden in a variety of processed and ultra-processed foods on the supermarket shelf and a person can still be consuming milk unbeknownst to them. It is important to highlight that focusing on the importance of a diet based on wholesome foods, which include a variety of food groups, with calcium being obtained from other sources of different food groups.

Lactose-free dairy are a great substitute for those who  want the same flavour and taste without the negative symptoms. Lactose-free dairy also contain the same amount of calcium as regular dairy products.

Some people who are lactose intolerant lean towards over the counter pills to halt or soothe oncoming symptoms. Lactaids, which are manufactured lactase enzymes, may help in digesting dairy products when taken at the right time.

Calcium Needs

The ‘no dairy diet’ can lead to calcium deficiencies if not properly compensated. Calcium is key for obtaining optimal bone health, as well as muscle growth, nerve functions and blood clotting. Below are calcium rich non-dairy/lactose free alternatives with their respective levels of calcium per serving size:

FoodFood GroupMg of Calcium per 100gMg of Calcium/per serving
Sesame seedsProtein975263 / 2 tbsp
Chia seedsProtein631179 / 2 tbsp
AlmondsProtein27376 / 2 tbsp
HazelnutsProtein11432 / 2 tbsp
Sardines with bonesProtein382275 / 6 sardines
Soybeans – edamameProtein197504 / 1 cup
ParsleyVegetable13883 / 1 cup chopped
Olives, blackVegetable8860 / 1/2 cup
BroccoliVegetable4635 / 1 cup
CeleryVegetable4040 / 1 cup chopped
CarrotVegetable3384 / 1 cup chopped
KaleVegetable25453 / 1 cup
FigsFruit162120 / 1/2 cup
MolassesSweetener20582 / 2 tbsp
Reference: https://fdc.nal.usda.gov

Vitamin D Needs

When avoiding dairy, calcium is not the only vitamin/mineral to be mindful of. Vitamin D is a necessary nutrient that builds and maintains healthy bones. Milk is a great source of Vitamin D, so switching to lactose-free milk will have the same nutritional qualities.

You can also obtain Vitamin D through sunlight, vitamin supplements, fatty fish and certain vegetables, such as mushrooms (if grown under UV light).


Students from the Culinary Management Nutrition Program at George Brown College Chef School participated in an academic writing content to create a lactose intolerance article for CDHF. The course, called Nutrition Issues, is taught by nutrition professor, Dr. Linda Gillis. Students highlighted the multicultural aspect of our nation and how lactose intolerance rates differ throughout Canada.  Their experience in planning meals using creative recipes is highlighted in this article.  Chante Grant and Mariana Schille were the winners for the contest.  George Brown College provides students with real world applications and opportunities for learning. Learn more more about Culinary Management Nutrition program.

Statistics on lactose intolerance

  • Lactose is a natural sugar found in milk. Individuals who are lactose intolerant lack the enzyme (lactase) to break down this sugar for absorption. Lactose then gets into the large bowel (colon) and may cause gas, bloating, diarrhea and abdominal cramping. Sometimes lactose intolerance occurs after digestive infections.
  • Lactose intolerance is associated with lower quality of life. (Casellas et al. 2016)
  • The true prevalence of lactose intolerance is unknown. In a national Canadian survey, 16% of participants perceived that they had lactose intolerence. (Barr 2013)
  • Lactose intolerance is more prevalent among African Americans, Hispanic Americans, Asian Americans, and Native Americans, and less common among those of European descent. (Suchy et al. 2010)
  • Elimination of milk and milk products is not necessary in lactose intolerance. In general, individuals may tolerate at least 12 g of lactose when administered in a single dose (equivalent to the lactose content in 1 cup of milk). Larger amounts of lactose may be tolerated if ingested with meals and distributed throughout the day. (Suchy et al. 2010)

Students from the Culinary Management Nutrition Program at George Brown College Chef School participated in an academic writing content to create a lactose intolerance article for CDHF. The course, called Nutrition Issues, is taught by nutrition professor, Dr. Linda Gillis. Students highlighted the multicultural aspect of our nation and how lactose intolerance rates differ throughout Canada.  Their experience in planning meals using creative recipes is highlighted in this article.  Chante Grant and Mariana Schille were the winners for the contest.  George Brown College provides students with real world applications and opportunities for learning. Learn more more about Culinary Management Nutrition program.

People who are lactose intolerant have unpleasant symptoms after eating or drinking milk or milk products. But why? Normally, when someone eats something that contains lactose, an enzyme that’s produced in your small intestine called lactase, breaks down lactose into its simpler components (which are simple sugars called glucose and galactose). These simple sugars are then able to be absorbed in the bloodstream and give you the energy you need.

If you have lactose intolerance, the body doesn’t make enough lactase to break down lactose, and as a result allows undigested lactose molecules to pass to the lower parts of the intestine. At this point, the undigested lactose encounter bacteria which begin digestion through a process of fermentation. The outcome of this fermentation (hydrogen, carbon dioxide, methane gases, and short-chain fatty acids) leads to many of the telltale symptoms for lactose intolerance – like gassiness and diarrhea. (1)

We’ve compiled a list of frequently asked lactose intolerance questions to help you further understand this digestive condition!

What are the types of lactose intolerance?

Lactase deficiency is a spectrum- some people are more deficient than others. Lactase deficiency can be primary, secondary, or congenital.

1. Primary lactase deficiency

This is the most common cause of lactose intolerance, and is most prevalent in adults. Most people have sufficient amounts of lactase at birth and in early childhood, when breast milk is the primary source of nutrition. In some people, the amount of lactase declines with aging; in others lactase production persists. This is a genetically inherited condition where the parent passes down a genetic mutation to child.

2. Secondary lactase deficiency

Injury to the lining of the small intestine may result in a deficiency of lactase and lactose intolerance, which is usually associated with other indications of bowel damage such as continuous diarrhea, intestinal bleeding, and weight loss. Further, intestinal infections such as Salmonella and parasites such as Giardia can result in lactose intolerance. Lastly, digestive conditions such as celiac disease and Crohn’s disease may include lactose intolerance as part of their symptoms. While most people with lactose intolerance have primary lactase deficiency, the possibility of an underlying intestinal disease should be looked at, especially if there is accompanying symptoms such as weight loss or low blood count (anemia).

3. Congenital lactase deficiency

This is a very rare inherited condition where lactase production is absent from birth. In this case, both parents have passed on the gene for lactose intolerance to their child, preventing the small intestine from producing enough lactase. Affected infants cannot tolerate milk products and must be nourished with non-milk formulas.

Is lactose intolerant genetically inherited?

Primary lactase deficiency and congenital lactase deficiency are both genetically inherited.

Primary lactase deficiency is a genetically inherited condition that involves passing down a genetic mutation from parent to child. It may seem like primary lactase deficiency is developed because symptoms may not appear until adulthood, but it is in fact hereditary.

Congenital lactase is also inherited. The genetic mutation responsible for congenital lactase deficiency is passed on in an autosomal recessive inheritance pattern. This means both parents must have a copy of the mutated gene to pass on the condition. (4)

Can lactose intolerance come and go?

Lactose intolerance will never fully go away for someone genetically predisposed to it.

That being said, it is possible to manage symptoms and many people find that their symptoms go away within a couple of days after decreasing the amount of dairy in their diet. (1)

Is lactose intolerance an allergy?

Lactose intolerance is NOT an allergy. A milk allergy is an immune response to protein in cows’ milk and results in skin rash, symptoms of inflammation of the esophagus or intestine or, occasionally with life-threatening anaphylaxis or shock. A food allergy happens when your immune system overreacts to a specific food protein, causing an allergic reaction. Unlike food allergies, food intolerances do not involve the immune system, but happen when an individual is missing the enzyme lactase. Milk allergies are generally diagnosed in the first year of life, while lactose intolerance occurs more often in adulthood. (2)

Can you suddenly become lactose intolerant?

It often manifests early in life, but it is not uncommon to develop later in life, seemingly out of the blue. As you get older (starting from the age of 2), the body generally produces less and less lactase. By adulthood, up to 70% of people no longer produce enough lactase to properly digest the lactose in milk, leading to symptoms when they consume dairy. This is particularly common for people of non-European descent. (3)

Is it possible that I have celiac disease as well as lactose intolerance?

It is possible. 25% of patients who have been clinically identified as lactose intolerant, have celiac disease. In Canada, that means about 73,500 people have undiagnosed celiac disease which is the causal agent for their lactose intolerance. If you think you have celiac disease, you should speak with your doctor.

Can I diagnose myself with lactose intolerance?

No. It’s important to listen to your body and know when to get help, but only medical professionals can assess if one is lactose intolerant or not. Medical professionals can also point you in the right direction, so that you do not end up with any deficiencies or misinformation.



References:

(1) NHS. 2016. Lactose Intolerance. https://www.nhs.uk/conditions/lactose-intolerance/

(2) Mayo Clinic Staff. 2018. Lactose intolerance.

mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232

(3) Torborg L. 2016. Mayo Clinic Q & A: Lactose intolerance can develop at any age.

newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-lactose-intolerance-can-develop-at-any-age/ (4) Malik, T. (2021) Lactose Intolerance.https://www.ncbi.nlm.nih.gov/books/NBK532285/

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