Lactose Intolerance After Metabolic and Bariatric Surgery

Lactose Intolerance After Metabolic and Bariatric Surgery - Bariatric Fusion

Did you know that food intolerances are common after metabolic and bariatric surgery (MBS)?

There are a few reasons MBS patients experience food intolerances, like lactose intolerance. Changes to the gastrointestinal tract during surgery can make it difficult for your body to absorb nutrients like lactose. In one study, almost 30% of post-op gastric bypass surgery patients experienced issues absorbing lactose. (1)

This article discusses common food intolerances post-op, specifically lactose intolerance, and how to manage gastrointestinal side effects.

Food Intolerance After MBS

Food sensitivities, or intolerances, refer to difficulty digesting a specific food. Intolerances are not to be confused with food allergies, as intolerances involve the digestive system and allergies affect the immune system. (2)

Common food intolerances include red meat, vegetables, bread, rice, pasta, and fish. Not everyone experiences intolerances, but if gastrointestinal symptoms occur, it might cause you to avoid meat, wheat, or dairy products that include essential nutrients your body requires. (3)

Generally, it’s not recommended to avoid any food groups unless advised by a medical provider or dietitian. Dietary counseling may be required to support a consistent protein, iron, and calcium intake from alternative food sources or supplements.*

What Causes Lactose Intolerance After MBS?

As we mentioned above, lactose intolerance is common after MBS. It happens because your body has difficulty absorbing it after surgery and has limited amounts of lactase enzyme. (1)

Let’s get into the science of why this happens. Lactose is broken down in the small intestine by an enzyme called lactase. After procedures like gastric bypass and duodenal switch, a portion of the small intestine is rerouted, limiting your body’s access to lactase. Plus, foods pass through the stomach and intestines at a higher rate after surgical alterations, limiting the time frame that digestive enzymes can mix with foods.

Symptoms of Lactose Intolerance

If there is insufficient lactase enzyme and lactose can move through the gut undigested, you can experience some side effects.

Here are some common symptoms associated with lactose intolerance:

  • Diarrhea
  • Bloating
  • Flatulence
  • Nausea
  • Abdominal pain
  • Vomiting

However, keep in mind that symptoms of lactose intolerance are very similar to that of dumping syndrome. Reach out to your healthcare provider for personalized recommendations if you experience any gastrointestinal side effects, as they should be evaluated on an individual basis after weight loss surgery.

The Difference Between Dairy-Free and Lactose-Free

Milk allergies are commonly confused with lactose intolerance, but as mentioned before, allergies and intolerances involve different body systems.

Milk products contain “derivatives” like whey, casein, and lactose. A milk allergy involves the immune system reacting to any milk derivative. In contrast, lactose intolerance is the digestive system reacting specifically to lactose.

As a reminder, lactose is the natural sugar found in milk products. It needs the enzyme lactase for proper digestion.

How can some products contain milk when they are also labeled lactose-free? While manufacturing whey protein isolate, special enzymes are added to heated milk, causing casein to turn solid and separate from the whey protein. When the whey protein liquid is left, it is washed and dried into a powder. This entire process allows for lactose to be undetectable.

For example, Bariatric Fusion high protein meal replacement powders contain whey protein isolate but are free from lactose – so you can drink it after weight loss surgery without issue.

If you are looking for more lactose-free protein shakes to support daily protein intake, you can find them here.*

the difference between dairy-free and lactose-free

What to Do if You Need to go Lactose-Free

If you know that you’re lactose intolerant, there are a few things you can do.

The best thing to do is avoid foods containing lactose (of course). You can also consider taking an enzyme alternative (Lactaid) to enjoy dairy products still or find a lactose-free dairy product.

Look for low-fat or fat-free dairy alternatives after metabolic and bariatric surgery, as your body has difficulty digesting fat. A few good products include:

  • Lactose-free milk
  • Almond milk
  • Peanut milk
  • Soy milk
  • Cashew milk

Some dairy products contain no lactose or are low-lactose and are better tolerated, such as:

  • Hard cheese (cheddar, swiss, and parmesan)
  • Kefir
  • Greek yogurt
  • Cottage cheese

You may also find foods fortified with calcium and vitamin D, such as orange juice. These make reasonable substitutions for dairy products because they contain similar essential vitamins and minerals.


It’s important to know that specific food intolerances are common after gastric surgeries so that you can be on the lookout for signs and symptoms.

Fortunately, side effects are typically mild and can easily be managed with a few lifestyle changes under the guidance of your healthcare team.


  1. Scand J Gastroenterol. 2020; 55(12):1398-1404 [PMID: 33096008]
  2. American Academy of Allergy Asthma & Immunology. 2022
  3. 24th IFSO World Congress. 2019

*These statements have not been evaluated by the Food & Drug Administration (FDA). These products are not intended to diagnose, treat, cure or prevent any disease.

This blog is for information and education purposes only. This information is not intended to substitute professional medical advice, diagnosis, or treatment. Please consult with your bariatric surgeon or another qualified healthcare provider with any questions in regards to a medical condition. A qualified healthcare professional can best assist you in deciding whether a dietary supplement is suitable based on your individual needs.

Enjoy our recipe and articles?

Have a great Bariatric Recipe?

Share your delicious and creative recipes with our community and help others achieve their health goals.