Irritable bowel syndrome (IBS) and lactose intolerance can cause similar symptoms in the digestive system. They include: 

• Diarrhea  

• Abdominal pain 

• Gas 

• Bloating 

Although their symptoms overlap, they are separate conditions with differences in how they are diagnosed and treated. 

IBS is a common condition that affects the stomach and intestines. It causes various symptoms, including: 

• Cramping that is related to the urge to poop 

• Excess gas 

• Mucus in the poop 

• Alternating diarrhea and constipation 

• The feeling of being unable to empty the bowels after pooping 

There are three types of irritable bowel syndrome, which are categorized based on how poops look on the days of having symptom flare-ups. They include: 

• IBS with constipation (IBS-C) causes most poop to be hard and lumpy 

• IBS with diarrhea (IBS-D) causes most poop to be watery and loose 

• IBS with mixed bowel habits (IBS-M) causes hard and lumpy, as well as watery and loose bowel movements 

Unfortunately, researchers don’t know what causes IBS. However, IBS is classified as a neurogastrointestinal disorder or a gut-brain interaction. A gut-brain interaction means there are problems with how the gut and brain coordinate to help the digestive system work. IBS can also be caused by: 

• An imbalance in the microbes that normally live in the digestive system 

• Emotional stress and adverse life events 

• An infection of the digestive tract, which includes common stomach bugs 

Lactose intolerance is a condition that occurs when people lack the enzyme lactase. This makes it difficult to digest lactose, which is the sugar present in milk and milk products.  

Lactose malabsorption is the inability to break down and absorb lactose molecules in the digestive system. Lactose malabsorption is common, as about 65% of adults worldwide can’t break down and absorb lactose.  

Lactose intolerance symptoms can appear inside and outside of the digestive system. Symptoms include: 

• Nausea and vomiting 

• Headaches 

• Fatigue 

• Joint pain 

• Problems concentrating 

• Mouth ulcers 

Primary lactose intolerance is inherited and is more common in certain ethnicities and parts of the world. In the U.S., African Americans, Latinx, Asian Americans, and Native Americans are more likely to suffer from lactose intolerance.  

Although it is uncommon, other forms of lactose intolerance are caused by disease or medications.  

IBS and lactose intolerance can be diagnosed without testing. A person’s health history is an important part of diagnosing these conditions.  

An IBS diagnosis is based on symptoms described in the Rome criteria, the guidelines used to diagnose gut-brain interaction, which includes stool changes, such as diarrhea, constipation, or a combination, and abdominal pain for at least one day each week during the previous three months. 

If these symptoms meet the Rome criteria, an IBS diagnosis can be made without the need for an invasive test such as a colonoscopy.  

However, further diagnostic testing would be needed if symptoms include blood in the stool, fever, and weight loss to determine if these are symptoms of another condition. 

The first steps in diagnosing lactose intolerance include a health history and physical exam. In some cases, a clear connection between a person consuming dairy products and symptoms can suggest a diagnosis of lactose intolerance.  

In certain cases, a breath test to diagnose lactose intolerance is available. During this test, a person drinks a solution that contains lactose and breathes to have their breath captured and measured for hydrogen. A higher level of hydrogen in the breath can indicate lactose intolerance. 

IBS treatment starts with diet and lifestyle changes, including: 

• Adopting a low-FODMAP diet, which is a diet that is low in certain carbohydrates such as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols 

• Eating more fiber 

• Avoiding caffeine and alcohol 

• Decreasing and managing stress 

• Identifying and avoiding foods that cause symptoms 

• Eating small meals on a regular schedule 

• Treating mental health conditions 

• Increasing physical activity 

• Trying a peppermint oil supplement 

If lifestyle and diet changes don’t help, many drugs could help, including: 

• Antidiarrheals 

• Antispasmodics 

• Laxatives 

• Selective serotonin reuptake inhibitors (SSRIs) 

• Tricyclic antidepressants (TCAs) 

• Other prescription drugs 

Treating lactose intolerance consists of avoiding foods that cause symptoms, dairy products that have less lactose or are lactose-free, or taking a supplement that breaks down lactose. 

If you or a loved one is experiencing symptoms associated with IBS or lactose intolerance, you can receive treatment at Flushing Hospital Medical Center’s Ambulatory Care Center. To schedule an appointment, please call (718) 670-5486. 

All content of this newsletter is intended for general information purposes only and is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment. Please consult a medical professional before adopting any of the suggestions on this page. You must never disregard professional medical advice or delay seeking medical treatment based upon any content of this newsletter. PROMPTLY CONSULT YOUR PHYSICIAN OR CALL 911 IF YOU BELIEVE YOU HAVE A MEDICAL EMERGENCY.