Lactose Intolerance 101

Lactose intolerance is a digestive disorder characterized by the inability to digest lactose, resulting in symptoms including diarrhea, gas and bloating.

January 09, 2020 4 minute read

According to the U.S. National Library of Medicine, about 65 percent of the human population has a reduced ability to digest lactose after infancy. Of that, the Cleveland Clinic, a nonprofit academic medical center in Ohio, estimates 30 to 50 million Americans have some degree of intolerance. 

Because lactose intolerance is more common than many may think, it’s important to know what it is, the symptoms, how to diagnose and treat it, what products contain lactose, and alternative sources of calcium. 

What is lactose intolerance?

Lactose intolerance is the inability to digest lactose, a sugar found in milk. Generally, lactose is broken down by the enzyme lactase into glucose and galactose, simpler forms of sugar then absorbed into the bloodstream.

What products contain lactose?

Lactose is found in cow’s and goat’s milk and other dairy products including:

  • Cheese
  • Yogurt
  • Milk Solids
  • Milk Powder
  • Malted Milk
  • Cream
  • Buttermilk
  • Curds
  • Whey
  • Butter
  • Nougat

The most common foods high in lactose are milkshakes, whipped cream, pudding, cream soups, cream sauces, and ice cream. A few that contain small amounts of lactose are bread, milk chocolate, breakfast cereals, instant potatoes, lunch meats, and some candies. Lactose is also present in 20 percent of prescription medications and 6 percent of over-the-counter medications. 


After eating or drinking milk products, those with intolerance produce digestive symptoms. These begin a half hour to two hours after eating or drinking lactose products, and include:

  • Stomach pain
  • Bloating
  • Diarrhea
  • Excess Gas

Lactose intolerance is not a milk allergy, which is the immune system’s abnormal response soon after consuming milk accounting for one-fifth of all food allergies in children and infants. Symptoms include hives, wheezing, itching or swelling around the lips or mouth, vomiting, shortness of breath, or anaphylaxis.

Types of Lactase Deficiencies

Low lactase production by the small intestine can lead to lactose malabsorption, where lactose passes through the colon, bacteria breaks it down, and fluid and gas are created. 

  • Primary Lactase Deficiency: Lactase production declines over time, usually beginning at age 2. 
  • Secondary Lactase Deficiency: This intolerance is caused by small intestine injuries, including infection or disease.
  • Developmental Lactase Deficiency: This can occur for a brief period of time in premature infants. 
  • Congenital Lactase Deficiency: A rare disorder, babies are born with small intestines that produce little to no lactase due to inherited mutated LCT genes. 

How is lactose intolerance diagnosed?

Because symptoms can be signs of multiple conditions, a physician should be consulted to diagnose lactose intolerance. A doctor will ask about your symptoms, eating habits, medical history, and may also institute a dairy-free diet for a week or two to see if the symptoms disappear before administering tests. A physical exam checking for bloating, tenderness, or pain is also used. 

To properly diagnose intolerance, a doctor may administer one of two tests: 

A lactose tolerance test measures the body’s reaction to a liquid with high levels of lactose. A few hours later, a blood test will be conducted to check the glucose in the bloodstream. If glucose levels remain the same, lactose isn’t being digested properly. 

Similarly, a drink with high levels of lactose will be administered for a hydrogen breath test. High levels of hydrogen indicate lactose indigestion. 


There is no treatment for lactose intolerance or increasing the body’s production of lactase. The U.S. National Library of Medicine has completed more than 20 clinical trials and is currently conducting five more to test the effects of various drugs and probiotics on lactose intolerance in hopes of finding a remedy. 

However, the condition can be managed by diet and limiting lactose consumption. 

Because everyone has different levels of intolerance, there is also no strict diet to adhere to. So, try going lactose-free for a few weeks and gradually reintroducing it back into your daily meals. Pay attention to how your body reacts to products with different levels of lactose. This way, you’ll know how much you can consume before experiencing symptoms. 

Avoid foods high in lactose and try not to drink more than half to one cup of milk at a time.

Consume a full meal with lactose-rich beverages or food, because solids slow down the digestive process and give lactase more time to break down lactose. 

Alternatives include substituting lactose-reduced or -free products such as Lactaid for regular dairy products, or purchasing over-the-counter lactase tablets and enzyme supplements consumable prior to lactose-heavy meals. 

However you choose to manage lactose intolerance, it’s important to find other sources of calcium. 

Lactose-free milk, cheese, and yogurt have the same amount of calcium as regular dairy products. Other good sources include calcium-rich soy, rice, and almond drinks; orange juice; vegetables such as broccoli and kale; beans, such as chickpeas and pinto beans; nuts, including almonds and sesame seeds; and canned fish with bones. Calcium supplements are also options, but consult a doctor before taking these. 

If you think you may have lactose intolerance, contact Gastroenterology Associates today. We can perform the necessary exams and tests to properly diagnose this digestive disorder. Gastroenterology Associates is conveniently located next to Long Island Center for Digestive Health (LICDH), a New York State-licensed non-hospital out-patient facility dedicated to providing endoscopic services in a comfortable environment. 

Topics: gastroenterology associates, Long Island Center for Digestive Health