Clinical Review

Understanding Lactose Intolerance

Clinician Reviews. 2010 November;20(11):17, 18, 20, 21

References

1. Shaukat A, Levitt MD, Taylor BC, et al. Systematic review: effective management strategies for lactose intolerance. Ann Intern Med. 2010;152(12):797-803.

2. Lomer MC, Parkes GC, Sanderson JD. Review article: lactose intolerance in clinical practice—myths and realities. Aliment Pharmacol Ther. 2008;27(2):93-103.

3. NIH Consensus Development Conference. Lactose intolerance and health: final statement. February 22–24, 2010; Bethesda, MD.

4. Heyman MB; American Academy of Pediatrics Committee on Nutrition. Lactose intolerance in infants, children, and adolescents. Pediatrics. 2006;118(3):1279-1286.

5. Eadala P, Waud JP, Matthews SB, et al. Quantifying the ‘hidden’ lactose in drugs used for the treatment of gastrointestinal conditions. Aliment Pharmacol Ther. 2009;29(6):677-687.

6. Swagerty DL Jr, Walling AD, Klein RM. Lactose intolerance. Am Fam Physician. 2002;65(9): 1845-1850.

7. Wilt TJ, Shaukat A, Shamliyan T, et al. Lactose intolerance and health. Evid Rep Technol Assess (Full Rep). 2010 Feb(192):1-410.

8. National Digestive Diseases Information Clearinghouse, National Institute of Diabetes and Digestive and Kidney Diseases, NIH. Lactose intolerance (2009). http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance. Accessed October 25, 2010.

9. Pray WS, Pray JJ. Lactose intolerance. US Pharmacist. 2004;29(6). www.medscape.com/viewarticle/482131. Accessed October 25, 2010.

10. Host A. Clinical course of cow’s milk protein allergy and intolerance. Pediatr Allergy Immunol. 1998;9(11 suppl):48-52.

11. Montalto M, Curigliano V, Santoro L, et al. Management and treatment of lactose malabsorption. World J Gastroenterol. 2006;12(2): 187-191.

12. Labayen I, Forga L, Gonzalez A, et al. Relationship between lactose digestion, gastrointestinal transit time and symptoms in lactose malabsorbers after dairy consumption. Aliment Pharmacol Ther. 2001;15(4):543-549.

13. Hovde O, Farup PG. A comparison of diagnostic tests for lactose malabsorption: which one is best? BMC Gastroenterol. 2009;9 82-88.

14. Srinivasan R, Minocha A. When to suspect lactose intolerance: symptomatic, ethnic, and laboratory clues. Postgrad Med. 1998;104(3): 109-111,115-116,122-123.

15. Arola H. Diagnosis of hypolactasia and lactose malabsorption. Scand J Gastroenterol Suppl. 1994;202:26-35.

16. Lin MY, Dipalma JA, Martini MC, et al. Comparative effects of exogenous lactase (beta-galactosidase) preparations on in vivo lactose digestion. Dig Dis Sci. 1993;38(11):2022-2027.

17. Hertzler SR, Savaiano DA. Colonic adaptation to daily lactose feeding in lactose maldigesters reduces lactose intolerance. Am J Clin Nutr. 1996;64(2):232-236.

18. Kudlacek S, Freudenthaler O, Weissboeck H, et al. Lactose intolerance: a risk factor for reduced bone mineral density and vertebral fractures? J Gastroenterol. 2002;37(12):1014-1019.

19. Segal E, Dvorkin L, Lavy A, et al. Bone density in axial and appendicular skeleton in patients with lactose intolerance: influence of calcium intake and vitamin D status. J Am Coll Nutr. 2003;22(3):201-207.

20. Johns A, Leijten P, Yamamoto H, et al. Calcium regulation in vascular smooth muscle contractility. Am J Cardiol. 1987;59(2):A18-A23.

21. Emory University, National Cancer Institute. Calcium/vitamin D, biomarkers, and colon polyp prevention (PPS4B). clinicaltrials.gov/ct2/show/NCT00399607. Accessed October 25, 2010.

Also playing a role are the patient’s gastric emptying time and intestinal transit time.¹² Symptoms of LI can be produced between 30 minutes and two hours after ingestion of milk or a milk product.⁹

Diagnosis
Most patients do not require specialized, sophisticated testing for a diagnosis of LI. A thorough medical history and physical examination are needed to rule out other conditions in the differential diagnosis (see Table 1^6,14). For the primary care provider, a basic workup should include a complete blood count, a comprehensive metabolic panel, erythrocyte sedimentation rate, a thyroid-stimulating hormone level, a stool culture, and if symptoms are severe, abdominal/pelvic radiography and CT.

In the absence of accepted guidelines, a common therapeutic approach is to exclude milk and dairy products from the patient’s diet.¹¹ Generally, a two-week trial of a strict lactose-free diet leading to resolution of symptoms, followed by reintroduction of dairy foods and recurrence of symptoms, can be considered diagnostic.⁴

It is important to instruct the patient that while he or she follows this diagnostic diet, all sources of lactose must be eliminated; food labels must be read carefully to identify “hidden” lactose sources (see Table 2⁸). Additionally, many patients (and even clinicians) may not realize that many commonly used prescription and OTC medications contain lactose, including certain agents indicated for gastrointestinal problems⁵ (see Table 3⁵).

During the diagnostic diet, patients may find it helpful to keep a diary of food choices and note any symptoms that may occur. This helps empower them to be an active participant in food choices, using self-experimentation to identify which foods they can and cannot tolerate.

Gastroenterology Consult
Referral to a gastroenterologist is needed if the diagnosis is unclear or if other illnesses are suspected. Tests the specialist may perform include the hydrogen breath test, a small-intestine biopsy, the lactose tolerance test, and/or the stool acidity test for infants and children,⁴ although these tests vary in sensitivity and specificity.¹³

The hydrogen breath test, by which enzymatic activity is confirmed after the patient consumes 25 to 50 g of lactose,⁶ is the most widely used formal test for confirming a diagnosis of LI because it is relatively inexpensive and is the most sensitive and the most specific for LI, according to Hovde and Farup¹³ and Eadala et al.⁵ The test has been shown to yield positive results in 90% of patients with lactose malabsorption.^6,15 False-negative results may signify absence of bacterial flora, as in the case of recent antibiotic use or a recent high-colonic enema. Previous aspirin use, sleep, exercise, and smoking may increase breath hydrogen secretion unrelated to lactose consumption.⁶

Management of Lactose Intolerance
Although the body’s ability (or inability) to produce lactase cannot be changed, the symptoms of LI can be managed with dietary restrictions. The extent of change needed depends on how much lactose the patient is able to consume before experiencing symptoms.⁸

In patients with secondary LI, a complete lactose-free diet is recommended until the causative pathologic condition has resolved. Patients with primary LI can opt to exclude all milk and dairy products, at least initially, until symptoms have resolved; they can then reintroduce certain milk and dairy products gradually and in small amounts, according to their individual tolerance threshold. Certain lactose-containing foods may be easier to digest than others (see Table 4²).

Ingesting lactose-containing foods with a meal helps decrease gastric transit time and can lessen the symptoms of LI.¹¹ Additionally, people who cannot drink milk may find they can eat yogurt because it contains lactase-producing bacteria,⁹ although clinical trials examining consumption of yogurt or probiotics in patients with LI had inconclusive results.¹

Lactose-free milk or soy milk is available at most major grocery stores. These products tend to be more expensive and taste somewhat sweeter than regular milk but can be used as a reasonable substitute.⁹

Some patients may benefit from taking lactase enzyme supplements,^1,16 which are taken with any ingestion of lactose. The enzymes may not completely prevent symptoms because the lactose is not completely digested or because it is difficult to determine an effective dose of the enzyme. Therefore, enzyme supplementation should be an adjunct to, not a substitute for, dietary restrictions.⁶ This may help patients when they eat at restaurants, where they do not know how food is prepared and which are unlikely to offer lactose-free food selections.

Instead of taking lactase enzyme supplements in tablet form, patients may prefer to mix lactase liquid with regular milk, producing lactose-free milk. A waiting period of 24 hours is needed before the mixture can be considered lactose-free. A trial-and-error period should be expected when enzyme supplementation or any dietary approach is tried.¹¹