Can lactose-free milk cause diarrhea?

In this short article, we will provide an answer to the question “can lactose-free milk cause diarrhea?” and the details about lactose intolerance.

Can lactose-free milk cause diarrhea?

Lactose-free milk is highly unlikely to cause diarrhea. Research indicates that consumption of lactose-free and lactose-hydrolyzed milk and dairy products tends to result in fewer to no gastrointestinal symptoms.

Symptoms such as bloating, flatulence, diarrhea, and abdominal pain, especially among lactose intolerant individuals were greatly diminished , in comparison to the consumption of lactose-containing milk and dairy products. (1)

The same isn’t true  for people who have cow’s milk protein allergy (CMPA), as lactose-free milk still has these proteins and can cause the same symptoms such as abdominal pain, vomiting, and diarrhea. (2)

Is lactose-free milk nutritional value comparable to that of regular milk?

Despite containing lactase, which aids in the digestion of lactose, lactose-free milk maintains a nutritional profile that closely resembles that of regular milk. 

This similarity makes lactose-free milk a valuable and nutritious beverage choice. It remains abundant in protein and calcium, both crucial for preventing osteoporosis and preserving muscle mass.

Additionally, lactose-free milk offers a diverse array of essential elements, such as riboflavin, phosphorus, vitamins A and B12, potassium, magnesium, and zinc. (2, 3)

What is lactose intolerance?

Lactose intolerance (LI) is a condition affecting the mucosa of the small intestine, hindering the digestion and absorption of lactose from the diet. This occurs either due to low activity or the absence of the lactase enzyme, β-D-Galactosidase, in the body.

Individuals with LI may experience various symptoms, including flatulence, abdominal discomfort, bloating, a feeling of swelling, nausea, borborygmus (stomach rumbling), vomiting, constipation, and watery diarrhea with acidic stools. 

In severe cases, LI can lead to dehydration, metabolic acidosis, and potentially malnutrition. (2)

Why lactose intolerance causes diarrhea and gasses?

The occurrence of diarrhea in LI stems from the failure to absorb or utilize lactose in the small intestine. This results in increased local osmolarity, attracting water and electrolytes to the mucosa, leading to intestinal dilatation and accelerated transit, which exacerbates malabsorption.

Subsequently, lactose accumulates in the colon, where intestinal microbiota ferment it, producing short-chain organic acids like acetic, butyric, and propionic acids, along with gasses such as methane, carbon dioxide, and hydrogen. 

These gasses contribute to flatulence, distension, and abdominal pain. The acidification of feces due to the formation of organic acids leads to liquid stools, causing further abdominal distension and perianal hyperemia. (2)

What is Cow’s milk protein allergy?

Cow’s milk protein allergy (CMPA) refers to an atypical immune response triggered by the proteins present in cow’s milk. This allergic reaction can be immediate and results from the interaction between various milk proteins and immune mechanisms.

Cow’s milk contains over 20 proteins that have the potential to induce allergic reactions, with casein and whey protein being the primary allergens. 

Individuals who experience this allergy typically react to nearly all types of animal milk because some of these proteins are also present in milk from other mammalian species. 

This cross-reactivity contributes to the allergic responses observed in people who are sensitive to animal milk proteins. (2)

What are Cow’s milk protein allergy symptoms?

The symptoms of CMPA can manifest either immediately or may appear after a few hours or days following the consumption of cow’s milk or infant formula. Gastrointestinal symptoms are the most common, occurring in 50 to 75% of cases, and typically include abdominal pain, vomiting, and diarrhea.

Around 50% of cases exhibit respiratory tract manifestations, such as runny nose, sneezing, coughing, or wheezing. Skin symptoms, including itching, edema, rash, or hives, are present in approximately 10 to 30% of individuals with CMPA.

Among the symptoms of CMPA, anaphylactic shock is the most severe and life-threatening. However, it is a relatively rare occurrence, affecting approximately 12% of cases, making it less common compared to other symptoms. (2) 

How is lactose-free milk made?

The production of lactose-free milk involves the addition of lactase enzymes to regular milk, following a series of carefully orchestrated steps. Initially, the milk undergoes pasteurization and is cooled to a temperature of 5 °C. 

Within a holding tank, enzymes are introduced to the milk, and it is left undisturbed overnight. The duration of this process varies, depending on the desired degree of lactose breakdown, usually aiming for 70% or complete hydrolysis.

Once the desired level is attained, the milk is subjected to a reheating process to deactivate the enzymes, known as ultra-pasteurization. Subsequently, the lactose-free milk is carefully packaged into retail containers. 

The ultra-pasteurization step plays a crucial role in significantly prolonging the shelf life of lactose-free milk when compared to regular pasteurized milk. This ensures that consumers can enjoy lactose-free milk for an extended period without concerns about spoilage. (4)

Other FAQs about Milk that you may be interested in.

Do Oreos Contain Milk

Does Oat Milk Make You Poop?

Does Nonfat Milk Have Lactose


In this short article, we provided an answer to the question “can lactose-free milk cause diarrhea?” and the details about lactose intolerance.


  1. Sharp, E. D’Cunha, N. M. Ranadheera, C. S., Vasiljevic, T., Panagiotakos, D. B., & Naumovski, N. Effects of lactose-free and low-lactose dairy on symptoms of gastrointestinal health: a systematic review. International Dairy Journal, 104936. 2020.
  2. Silva, A. R. A., Silva, M. M. N., & Ribeiro, B. D.  Health Issues and Technological Aspects of Plant-based Alternative Milk. Food Research International, 108972. 2020.
  3. Pereira, P. C., & Vicente, F.  Milk Nutritive Role and Potential Benefits in Human Health. Nutrients in Dairy and Their Implications on Health and Disease, 161–176. 2017.
  4. Mahoney, R. R. Enzymes Exogenous To Milk In Dairy Technology | Beta-d-Galactosidase. Encyclopedia of Dairy Sciences, 907–914. 2002.