Lactose intolerance and dairy allergies

Find out the differences between lactose intolerance and dairy allergies and which foods to exclude from the diet.
Published 18 May 2018

What is lactose intolerance?

Lactose intolerance is a digestive problem where the body is unable to digest lactose. Lactose is a type of sugar mainly found in dairy products, such as milk. Most people with lactose intolerance can usually handle small amounts of lactose but this differs from person to person.

Lactose can be hidden in these products

  • Breakfast cereals
  • Cakes and biscuits
  • Muesli bars and coatings
  • Cheese sauce
  • Pancakes and pikelets
  • Quiche
  • Scrambled eggs
  • Creamy soups
  • Chocolate
  • Some breads and margarine

WeightWatchers® expert advice: You can make a lot of our recipes lactose-free or dairy-free simply by swapping dairy products (such as milk) for lactose-free or nondairy alternatives (such as soy milk) or omitting toppings such as sour cream and yoghurt.

Lactose intolerance causes and symptoms

Lactose, the sugar in milk, frequently is blamed, and milk is the first item to be cut out of the diet, by people who have persistent abdominal discomfort after eating.

Lactose intolerance is caused by an inability to break down lactose into its two component sugars, glucose and galactose. Undigested lactose passes into the colon, where it is fermented by bacteria that release gases and other metabolic compounds that contribute to intestinal discomfort.

Lactose intolerance differs from milk allergy in that milk allergy is an immune reaction to the protein in milk while lactose intolerance is an intestinal reaction to the carbohydrate.

African-Americans, Hispanics, American Indians, and Asian-Americans are more likely to be lactose intolerant, and the condition is more common in adults than children.

The symptoms of lactose intolerance include abdominal pain, bloating, gas, diarrhea, and nausea – usually develop within 30 minutes to 2 hours after consuming milk or milk products and can be affected by the amount of lactose, whether the milk product was consumed with or without food, gastric emptying time, and individual variability.

Diagnosing lactose intolerance

Lactose intolerance usually cannot be diagnosed solely on symptoms, which are similar to those for irritable bowel syndrome and other conditions. A logical first step is to eliminate milk and milk products to see if symptoms improve and then to gradually add it back to see if symptoms return.

The hydrogen breath test measures hydrogen after ingesting a known dose of lactose; high levels of breath hydrogen suggest that bacteria are fermenting undigested lactose. However, people whose hydrogen breath test is positive may not complain of gastrointestinal symptoms and many who do report symptoms test negative for breath hydrogen.

Dietary management

Scientific evidence suggests that people who are lactose intolerant can handle the amount of lactose in a cup of milk with only minor symptoms and can tolerate even more when it is consumed with other foods throughout the day. As people differ in their ability to tolerate lactose, some will have discomfort while others will not. One strategy is to start with small amounts of milk and gradually increase portion size over time. Additionally, hard cheese, which has much less lactose than milk, and yoghurt – its bacteria break down lactose – may be well-tolerated.

Lactose-free and lactose-reduced milk and milk products can be used in place of regular milk. Lactase enzyme tablets taken with milk products also may alleviate discomfort. Soy milk, almond milk, rice milk, and coconut milk offer an alternative to cow’s milk for those who continue to have symptoms with the treated milk. But because fluid cow’s milk is the top source of calcium and vitamin D in the diet, people who avoid milk should make sure that any milk alternatives contain these important nutrients. Non-milk sources of calcium include tofu, dark green leafy vegetables, and fish canned with bones (the bones soften in the canning process and can be eaten).

Dairy allergy

A true dairy allergy, which prompts an autoimmune response from the body, is different from lactose intolerance, which is an inability to digest lactose. With allergies, milk’s protein is usually the culprit and must be avoided — which rules out many processed foods, since milk derivatives are commonly used. Many dairy substitutes include coconut, soy and almond milk.