Patient Presentation
A 6-year-old African-American female came to clinic with a history of intermittent abdominal pain. She had a history of intermittent constipation that was treated successfully when needed by polyethylene glycol 3350. The abdominal pain occurred several times per week at different times of the day and had been more frequent over the past few weeks. It did not awaken her from sleep. Her mother noticed it mainly after meals and she continued to have a good appetite. There was no diarrhea or emesis. They denied excessive flatulence usually but this also appeared to occur from time to time. The pain was not worsening in severity or frequency. Usually she would state that her abdomen hurt, point to her umbilicus and would want to cuddle with her parents. It would seem to go away after various time periods. In general it didn’t affect her activities. The mother said she had not noticed any correlation with stooling pattern and the patient had been having soft stools daily. She hadn’t been treated for constipation for at least 6 months. “Just this last week, I maybe noticed that it happens when she drinks a lot of milk or has a lot of dairy products. I am lactose intolerant and so is my sister. I hadn’t thought about that before. I was diagnosed with a breath test. Do you think we can do one?” the mother asked.
The pertinent physical exam showed a happy female with normal vital signs and who was growing at the 50% for all measurements. She was appropriately gaining weight. Her physical examination was normal including her abdominal exam and external genital and anal examination.
The diagnosis of intermittent abdominal pain was made. The pediatrician noted that this could be due to many things including unrecognized constipation, viral illness which was less likely given no acute symptoms, and possibly some type of food intolerance including lactose intolerance. “Lactase is the enzyme that breaks down lactose in food as you probably know. The amount of lactase decreases usually as we get older and some people genetically have less of it than others, including people who are African-American. Doing the breath test is hard for a lot of reasons in kids and may not be accurate so in general we don’t do it. Instead, what I want you to do is to keep a symptom diary of what she is eating, her stools, and her symptoms for 3-4 days. We’ll go over it, but it sounds like you already know about using lactose-free milk or following a low-lactose diet. Let’s see if there are any changes with that type of diet for her. Why don’t you do that for about a week or two and then followup with me and we’ll see how she is doing. We’ll also go over what to do if she is getting worse before then,” the pediatrician counseled.
The patient’s clinical course after 3 weeks revealed that she seemed to have symptoms with large amounts of milk (e.g. with cereal) but slightly better when eaten with other foods. When her mother changed her to lactose-free milk, she didn’t have abdominal pain either. “She went to a birthday party and ate a lot of ice cream and then had the belly pain, so for me that seemed be a clear reason for her pain. I’m going to keep her on the lactose-free milk and continue to watch her,” said the mother.
Discussion
Lactose is a sugar that is commonly found in dairy products. It is digested by the enzyme lactase mainly found on the brush border of the small bowel. Lactase production varies by age and genetics, with infants and young children having a generally higher amount than older children and adults, presumably as they have a more dairy-based diet. There is decreased production starting around 2-3 years of age (i.e. lactase non-persistence). Some people continue to produce lactase at the same levels as infants (i.e. lactase-persistence. “Lactase persistence (lactose tolerance) is seen predominantly in individuals with northern European ancestry, especially Scandinavian, and in certain other populations, including some of the nomadic peoples of the middle east and Africa. Lactase non-persistence (lactose intolerance) is observed in a majority of the world’s populations, including most of those with Asian or African forebearers.”
A 2018 scoping review found that “there is insufficient evidence to support any unique associations between [lactose intolerance] symptoms and gender, age or race, except for the expected differences due to genetically determined [lactase non-persistence].” Body size, dose and genetic difference in lactase non-persistence are the main factors of symptoms.
Congenital lactase deficiency is not very common but does occur due to genetics of the LCT gene. Primary lactose intolerance is due to the normal developmental changes discussed above, while secondary lactose intolerance is due to small bowel problems such as viral or inflammatory conditions that temporarily decrease the amount of lactase produced.
Lactose intolerance symptoms usually occur within 30-120 minutes of a lactose-rich meal with problems such as bloating, nausea, diarrhea, cramping, and flatulence.
Most people can tolerate some dairy products and these symptoms can be ameliorated by smaller amounts ingested with a meal, along with eating other foods at the same time. Diets that are low in lactose can be more expensive though. A study in Germany found food cost increased with the severity of the lactose intolerance and ranged from 0.2 to 6.1% increased food cost/month. They found that “…switching from a normal diet to a lactose reduced diet, while simultaneously meeting nutrient requirements, is to substitute regular milk by its lactose-free variant.” Switching to other calcium-rich foods is often suggested but is even more expensive than switching to lactose-free dairy products. Lactase drops can also be added to regular milk to render it lactose-free. The amount needed per unit of milk and the cost varies widely.
For some people with lactose intolerance as little as 3 grams of lactose can induce symptoms but most people can tolerate at least 12 grams without a concurrent meal. There is approximately 12-14 grams of lactose in 8 ounces of milk. Lactose in water-based solutions (i.e. milk) is better tolerated than in other forms usually. Usually when consumed with a meal, 18 grams tolerated and up to 70 grams/day in divided doses is also usually tolerated.
Learning Point
Hydrogen breath tests can be very helpful in diagnosing lactose intolerance but can have false-positive or false-negative results due to a variety of reasons. There are many factors involved in these accurate testing including preparation for the test (e.g. recent drugs, certain foods ingested, probiotics, fasting timing, etc.), test meal standards, sample acquisition, need for repeated measurements, hydrogen only or hydrogen and methane testing, measurement cut-off values, and other problems such as oral hygiene or small bowel intestinal overgrowth and even intestinal transit times can affect the results.
The 2021 European Guidelines for hydrogen breath tests note that “[in] pediatric patients there is not a strong correlation between symptoms and the activity of lactase.” “H2 breath testing with symptom assessment shall be performed in children with uncertain correlation between food containing lactose or fructose and gastrointestinal symptoms.” “H2 breath testing does not need to be performed in children with a clear correlation between ingestion of a specific carbohydrate and gastrointestinal symptoms, as document by relief of symptoms when this carbohydrate is avoided and recurrence of symptoms when the carbohydrate is reintroduced in the diet.”
Questions for Further Discussion
1. What are FODMAPS? A review can be found here
2. What is differential diagnosis of acute abdominal pain? A review can be found here
3. What are your indications for referral to a gastroenterologist?
Related Cases
- Disease: Lactose Intolerance
- Symptom/Presentation: Abdominal Pain
- Specialty: Gastroenterology
- Age: School Ager
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for these topics: Lactose Intolerance and Malabsorption Syndromes.
To view current news articles on this topic check Google News.
To view images related to this topic check Google Images.
To view videos related to this topic check YouTube Videos.
Lapides RA, Savaiano DA. Gender, Age, Race and Lactose Intolerance: Is There Evidence to Support a Differential Symptom Response? A Scoping Review. Nutrients. 2018;10(12):1956. doi:10.3390/nu10121956
De Geyter C, Van de Maele K, Hauser B, Vandenplas Y. Hydrogen and Methane Breath Test in the Diagnosis of Lactose Intolerance. Nutrients. 2021;13(9):3261. doi:10.3390/nu13093261
Hammer HF, Fox MR, Keller J, et al. European guideline on indications, performance, and clinical impact of hydrogen and methane breath tests in adult and pediatric patients: European Association for Gastroenterology, Endoscopy and Nutrition, European Society of Neurogastroenterology and Motility, and European Society for Paediatric Gastroenterology Hepatology and Nutrition consensus. United Eur Gastroenterol J. 2021;10(1):15-40. doi:10.1002/ueg2.12133
Taeger M, Thiele S. Additional costs of lactose-reduced diets: lactose-free dairy product substitutes are a cost-effective alternative for people with lactose intolerance. Public Health Nutr. 2021;24(13):4043-4053. doi:10.1017/S1368980021002779
Bowen Richard, Lactose Intolerance (Lactase Non-Persistence). Available from the Internet at: http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/lactose_intol.html, Cited 6/5/23, rev 7/22.
Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa