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Navigating Lactose Intolerance: Unveiling Its Impact on Digestive Health and Uncovering Hidden Sources

Keren Reiser, RD

Written by: Keren Reiser, RD

Updated: May 27th, 2024

“Your Digestive Health: Make It A Priority” is the 2024 theme for World Digestive Health Day on May 29th, 2024. The World Gastroenterology Organization estimates that between 57% to 65% of the world’s population has difficulty digesting lactose, the natural sugar in dairy products. Many people will self-diagnose lactose intolerance and follow a lactose-free diet without understanding why their gut can’t tolerate lactose and the consequences of eliminating an entire food group, like dairy foods.

Further, ethnicity, diet, and genetics play a significant role in why some people experience digestive discomfort from lactose. If you think you may be lactose intolerant check out our “Am I Lactose Intolerant Quiz and speak to your doctor.

This article will discuss navigating lactose intolerance, its impact on digestive health, food labelling requirements and strategies for uncovering hidden lactose sources in food and medications.

Keep reading to learn more!

What is Lactose Intolerance?

Lactose is a natural, double sugar chain found in animal dairy products. Whereas, lactase is the protein enzyme produced in the small intestine that breaks down lactose. Lactose intolerance occurs when the double sugar bond is not broken down by the lactase enzyme in the small intestine, and undigested lactose travels to the large intestine (colon).

It is crucial to make the distinction that lactose intolerance is not at all related to or the same as a cow milk dairy allergy. The symptoms are functional and result from the interaction of the undigested lactose with the gut microbiome rather than an immune reaction that can occur with an allergy.

Most humans are born with the ability to produce lactase; however, some ethnicities, genetics, and dietary factors lead to a decrease in lactase production, preventing the breakdown of lactose. This is often referred to as primary lactase deficiency.

Alternatively, secondary lactase deficiency can occur when lactase enzyme production decreases or lacks due to disease, illness, or injury to the small intestine. With secondary lactase deficiency, as the small intestine heals from an illness, lactase production can resume, meaning that lactose intolerance could be temporary.

Further, when lactose is not broken down by lactase in the small intestine, it travels through the digestive tract to the colon, known as the large intestine. This is called lactose malabsorption and leads to uncomfortable symptoms like stomach cramps, bloating, and gas after eating dairy foods. Since this process can happen relatively quickly, it can happen as fast as 30 minutes after eating a food that contains lactose. 

The Impact of Lactose on Gut Health

Regarding gut health, lactose intolerance is more than a dietary inconvenience or a diet change. When lactose is not properly digested, it can significantly impact gut health in various ways, including gut microbiome disruption, digestive discomfort, and nutritional deficiencies.

The Gut Microbiome

The gut microbiome is a complex and dynamic community of trillions of microorganisms, including bacteria, viruses, fungi, and other microbes, residing in the digestive tract, predominantly in the colon.

Ultimately, these microorganisms play a crucial role in various aspects of health, from aiding in the digestion of food and the absorption of nutrients to supporting the immune system and protecting against pathogenic bacteria. 

The gut microbiome is highly diverse and individualized, with its composition influenced by factors such as:

Maintaining a balanced gut microbiome is essential for overall health, as imbalances, often called gut dysbiosis, can lead to digestive issues like:

Emerging research continues to uncover the profound impact of the gut microbiome on both physical and mental health, highlighting its significance as a central component of human well-being​.

Lactose and the Gut Microbiome

Lactose not broken down by the lactase enzyme in the small intestine, travels to the large intestine (colon), referred to as lactose malabsorption. Lactose malabsorption leads to the growth of lactose-fermenting bacteria such as Bifidobacterium and Lactobacillus. The increase in lactose-fermenting bacteria can change the gut microbiome’s diversity, balance, and function.

When these bacteria break down undigested lactose in the colon, they produce gases like:

This gas buildup can cause symptoms like bloating, gas, and stomach pain. Moreover, the undigested lactose can also draw water into the colon, leading to diarrhea. This disruption causes immediate discomfort and can lead to longer-term imbalances in the gut microbiome, worsening other digestive problems and affecting overall gut health​ (6).

Nutritional Management of Lactose intolerance

For those with lactose intolerance, the first step in management typically involves reducing or eliminating lactose-containing foods from the diet. Since lactose digestion tolerance varies among people, some people can handle small amounts of lactose without symptoms.

However, repeated symptoms such as bloating, gas, diarrhea, and abdominal pain usually lead to the elimination of the entire dairy food group. Many do not realize that this can negatively impact digestive health and lead to a lack of essential dietary nutrients(3).

Dairy products are significant sources of essential nutrients such as calcium, vitamin D, phosphorus, and vitamin B12, vital for bone health. Completely eliminating dairy from the diet without finding alternative nutritionally equivalent food sources can lead to deficiencies and increase the risk of developing bone-related disorders.

For example, conditions like osteopenia and osteoporosis decrease bone density and increase fragility, making fractures more likely.

Notably,  lactose-free products are formulated to provide the same nutritional content as traditional dairy products, ensuring that individuals with lactose intolerance can still receive essential nutrients without experiencing digestive discomfort.

Lactose-free dairy foods have the same level of calcium, vitamin D, protein, and other vital nutrients found in traditional dairy milk and dairy products.

In short, the primary difference with lactose-free dairy products is they contain added lactase enzyme which breaks down lactose into simpler sugars, glucose and galactose. Thus, making them easier to digest for those with lactose intolerance.

In summary, the nutritional quality of lactose-free dairy products is unchanged, allowing people to enjoy the health benefits of dairy without the loss of essential nutrients.

To ensure nutritional adequacy on a lactose-free diet, nutritionally equivalent sources are needed. Here are some non-dairy calcium rich food sources:

Further Nutritional supplements may also be needed to prevent nutrient deficiencies. Supplements are not always absorbed as well as natural food sources, so a food first approach should play a key role in a balanced diet for someone with lactose intolerance.

Lactose Labeling in Canada:

In Canada, Health Canada sets the rules for labelling lactose in food products. The guidelines set rules for specific claims related to the presence or absence of lactose. Understanding the definitions of these terms is important for those with lactose intolerance to make informed dietary choices.

  1. Lactose-Free Claims: A product can be labelled “lactose-free” if no lactose is detectable using accepted analytical methods.
  2. Lactose-Reduced Claims: Products with significantly reduced lactose content (by at least 25%) can be labelled as “lactose-reduced.”
  3. Dairy Products Standards: If a dairy product, like milk, has the lactase enzyme added to it, the label must show this change and it should be labeled as “lactose-free milk”.
  4. Use of Lactase in Standard Products: If a product like ice cream is allowed to have lactase added to it, the label can either use its regular name or show that it has added lactase, such as “lactose-free ice cream”.

Lactose Labeling Requirements:

The Canadian Food Inspection Agency (CFIA) is responsible for enforcing labeling standards in Canada to protect consumers with lactose intolerance from exposure to unwanted lactose and assist them in making informed dietary choices.

However, the CFIA does not set specific criteria for how much lactose reduction qualifies a product to be labelled as “lactose-free” or “lactose-reduced”. Rather, the agency provides guidance on what products must adhere to in order to make these claims.

To ensure compliance, the CFIA conducts regular inspections and product testing to verify that the claims made on food labels are accurate. This enforcement helps maintain consumer trust and ensures industry compliance with the labelling standards.

Further, the CFIA publishes up-to-date recall warnings and alerts on their website and social media to inform consumers.

Moreover, the CFIA website has a searchable database and subscription service for recall information. Each recall notice includes detailed information about the product, including the name, brand, size, UPC code, and the specific nature of the risk (e.g., undeclared lactose).

In addition to announcing recalls, CFIA provides guidance on what consumers should do if they have purchased a recalled product. This might include instructions to return the product to the place of purchase or to dispose of it safely.

lactose labelling in canada

Hidden Sources of Lactose

Did you know there are hidden sources of lactose added to non-dairy food and medication products? The industry commercially uses lactose as a filler, stabilizer, or sweetener. It enhances texture and flavour, extends shelf life, and is a browning agent in baked goods.

Here are some common sources of hidden lactose if you are particularly sensitive to lactose:

  1. Processed Foods: Many processed foods contain lactose. These include bread, breakfast cereals, soups, instant potatoes, and salad dressings.
  1. Processed Meats: Lactose is found in meats like sausages, bacon, and deli meats and is used as a binder or to enhance flavour.
  1. Medications: Both prescription and over-the-counter medications may use lactose as a filler. Specifically, it’s commonly found in birth control pills, tablets for stomach acid and gas, and other medications.
  1. Baked Goods: Lactose is often added to baked goods to help with the browning process and improve taste and texture.
  1. Sweets and candies: might contain lactose to enhance creaminess and mouthfeel.
hidden sources of lactose

Strategies to Identify Hidden Lactose

  1. Read Ingredient Labels Carefully: Always check the ingredient list on food packages. Look for ingredients like milk, lactose, whey, curds, milk by-products, dry milk solids, and nonfat dry milk. Ingredients are listed by quantity, from highest to lowest.
  1. Know the Synonyms: Lactose can appear under different names such as milk sugar, whey, and casein. Familiarizing yourself with these terms can help you spot lactose even when it’s not explicitly listed.
  1. Check for “Contains” Statements: Many products have allergen statements such as “contains milk,” which can alert you to the presence of lactose.
  1. Be Aware of Common Sources: Besides dairy products, lactose can be found in less obvious foods like processed meats, bread, salad dressings, medications, and supplements.
  1. Ask Manufacturers: If you’re unsure whether a product contains lactose, contact the manufacturer directly for clarification. They can provide the most accurate and detailed information about their ingredients.
  1. Use Lactose-Free Labels: Products labelled “lactose-free” are safe for lactose-intolerant individuals. However, “dairy-free” does not necessarily mean lactose-free, as some dairy-free products might contain lactose from other sources.
  1. Consider Cross-Contamination: In restaurants and food production facilities, normally lactose-free foods might come into contact with lactose-containing foods. Thus, always inquire about food preparation methods if cross-contamination is a concern.
  1. Stay Informed About Food Processing: Understanding how foods are processed can help you identify less obvious sources of lactose. For example, “natural flavours” and “modified food starch” in processed foods can sometimes contain lactose.
  1. Use Resources: Utilize online resources, frequently asked questions, apps, and books that list lactose-containing foods and ingredients. These can be invaluable tools when shopping or eating out.
  1. Educate Those Around You: Make sure that your family, friends, and coworkers understand what lactose intolerance is and the importance of avoiding lactose in your diet. This can help prevent accidental exposure when others prepare food.
identify hidden lactose intolerance

Your Digestive Health: Make It A Priority

In summary, lactose malabsorption can impact the gut microbiome, and dietary interventions, like consuming lactose-free foods are recommended.

If you are particularly sensitive to lactose, read food labels carefully and review other products like medications for hidden sources of lactose.

Unsure if you are sensitive to lactose? Check out our Am I Lactose Intolerant Quiz and book an appointment with your doctor or dietitian.


(1) Ahn SI, Kim MS, Park DG, Han BK, Kim YJ. Effects of probiotics administration on lactose intolerance in adulthood: A meta-analysis. J Dairy Sci. 2023;106(7):4489-4501. doi:10.3168/jds.2022-22762

(2) Casciano F, Nissen L, Chiarello E, Di Nunzio M. In vitro assessment of the effect of lactose‐free milk on colon microbiota of lactose‐intolerant adults. International journal of food science & technology. 08/2023;58(8):4485-4494. doi: 10.1111/ijfs.16253

(3) Di Salvo, E., & Cicero, N. (2024). Could lactose-free foods influence the gut microbiome? Natural Product Research, 1–2.

(4) Facioni, M.S., Raspini, B., Pivari, F. et al. Nutritional management of lactose intolerance: the importance of diet and food labelling. J Transl Med 18, 260 (2020).

(5) Vitellio P, Celano G, Bonfrate L, Gobbetti M, Portincasa P, De Angelis M. Effects of Bifidobacterium longum and Lactobacillus rhamnosus on Gut Microbiota in Patients with Lactose Intolerance and Persisting Functional Gastrointestinal Symptoms: A Randomised, Double-Blind, Cross-Over Study. Nutrients. 2019; 11(4):886.

(6) Brandao Gois MF, Sinha T, Spreckels JE, et al. Role of the gut microbiome in mediating lactose intolerance symptoms. Gut 2022;71:215-217.