Lactose Intolerance vs. A1 protein intolerance

Consumers, even some trained healthcare professionals, may assume if they have discomfort after drinking milk that they are lactose intolerant without being tested to get a confirmed diagnosis. Nonetheless, restricting or eliminating milk from the diet results in relief from symptoms. However, according to the National Institute of Health*, dairy products provide a package of essential nutrients that is difficult to obtain in low-dairy or dairy-free diets. Moreover, some clients can’t or won’t give up milk and other dairy foods, even if they cause digestive distress.

Before asking clients to restrict or eliminate dairy, consider the following about Lactose Intolerance:

The Basics

Lactose intolerance is a condition in which you have digestive symptoms—such as bloating, diarrhea, and gas—after you consume foods or drinks that contain lactose. Lactose is a sugar that is naturally found in milk and milk products, like cheese or ice cream.

In lactose intolerance, digestive symptoms are caused by lactose malabsorption. Lactose malabsorption is a condition in which your small intestine cannot digest, or break down, all the lactose you eat or drink.

Not everyone with lactose malabsorption has digestive symptoms after they consume lactose. Only people who have symptoms are lactose intolerant (NIH

Lactose Malabsorption

According to a systematic review and meta-analysis published in the Lancet in 2017, about 68% of the world’s population has lactose malabsorption and 36% of people in the US have lactose malabsorption; this does NOT mean that these populations have Lactose Intolerance.

What Causes Lactose Malabsorption?

The symptoms of Lactose Intolerance are caused by lactose malabsorption. In lactose malabsorption, the small intestine makes low levels of lactase (the enzyme that breaks down lactose) which means that the lactose from food and drink is not digested completely.

Undigested lactose passes into the colon where friendly bacteria break it down into water and gas. In some people, this water and gas causes lactose intolerance symptoms like bloating, gas and diarrhea.

Anything that reduces the amount of lactase produced in the small intestine can cause lactose malabsorption which may result in lactose intolerance symptoms.

Causes of Lactose Intolerance

• Injury to the small intestine: Infections, diseases and other inflammatory conditions may reduce the ability of the intestine to produce lactase. Treatments like medications, surgery or radiation therapy may also injure the small intestine. Lactose intolerance caused by injury to the small intestine is called secondary lactose intolerance. If the cause of the injury is treated, people may be able to tolerate lactose again.
• Genetics: Some people carry a gene that helps them produce lactase, thus digest lactose. People who do not have this genetic predisposition have “lactase nonpersistance”, which means that their bodies’ ability to make lactase decreases with age. In this case, symptoms of lactose intolerance may not begin until later childhood, the teen years or early adulthood. Lactase nonpersistence, also called primary lactase deficiency, is the most common cause of low lactase levels.
• Premature birth: In premature babies, the small intestine may not make enough lactase for a short time after birth. Babies usually recover the ability to produce lactase in time.
• Congenital lactase deficiency: Is a rare genetic condition in which the small intestine makes little or no lactase, starting at birth.

Milk Allergies are NOT due to Lactose

Milk allergies are caused by the immune system’s response to one or more proteins in milk and milk products. Milk allergies usually appear within the first year of life, while lactose intolerance typically appears later. Allergic reactions to milk proteins can be life threatening.

Diagnosing Lactose Intolerance

Diagnosing lactose intolerance can be tricky. While there are tests for lactose malabsorption, some people diagnose themselves with lactose intolerance by eliminating milk and dairy foods, then watching for GI symptoms. If uncomfortable GI symptoms disappear, people usually blame it on lactose.

When a healthcare professional is involved, lactose intolerance should be diagnosed by assessing symptoms and triggers and by ruling out the presence of other health problems like IBS, celiac disease, Crohn’s, Ulcerative Colitis or SIBO (small intestine bacterial overgrowth). In addition, a physician can order a hydrogen breath test to determine if lactose is being malabsorbed.

Hydrogen Breath Test

To diagnose lactose malabsorption, doctors can use the Hydrogen Breath Test (although it is not often covered by insurance). It’s based on the fact that if lactose is not absorbed normally, there is a higher amount of hydrogen exhaled than normal.

For this test, patients drink a liquid with a known amount of lactose. Every 30 minutes, the patient breaths into a balloon-type container that measures the amount of hydrogen in the breath. During this time, the doctor or other healthcare professional should be asking questions about symptoms. If both breath hydrogen levels are elevated AND symptoms are present and get worse throughout the test, then the diagnosis is Lactose Intolerance.


Effects of Dairy Products Consumption on Health
Bayless TM, Brown E, Paige DM. Lactase non-persistence and lactose intolerance. Current Gastroenterology Reports. 2017;19(5):23.
Luyt D, Ball H, Makwana N, et al; Standards of Care Committee (SOCC) of the British Society for Allergy and Clinical Immunology (BSACI). BSACI guideline for the diagnosis and management of cow’s milk allergy. Clinical and Experimental Allergy. 2014;44(5):642–672.
Misselwitz B, Fox M. What is normal and abnormal in lactose digestion? The Lancet. Gastroenterology & Hepatology. 2017;2(10):696–697.
Savaiano, et al., Lactose intolerance symptoms assessed by meta-analysis: a grain of truth that leads to exaggeration. J Nutr. 2006;136(4):1107-13.
Storhaug CL, Fosse SK, Fadnes LT. Country, regional, and global estimates for lactose malabsorption in adults: a systematic review and meta-analysis. The Lancet. Gastroenterology & Hepatology. 2017;2(10):738–746.

Sign up for our newsletter

Copyright © 2022 The a2 Milk Company (USA)

*A1 and A2 proteins refer to A1 and A2 beta-casein protein types

a2 Milk® is a registered trademark of, and brand of A1 protein-free milk from, The a2 Milk Company Limited