Managing lactose intolerance

What is lactose intolerance?Lactose intolerance occurs when the body produces inadequate amounts of lactase enzyme (hypolactasia). Lactase is produced in the brush border cells of the small intestine and deficiency occurs when these cells are damaged by medical conditions such as inflammatory bowel disease or gastroenteritis. In these cases, lactose intolerance is likely to be transient and will only last until the inflammation to the brush cells has passed and the cells restored, which usually takes up to 6 weeks.

A significant proportion of the population have a genetic predisposition to lose lactase activity some time after infancy. This increases the likelihood that lactose intolerance will manifest itself, and it is likely to last longer than occurrences following acute inflammation.

 The result of hypolactasia is as follows:

• Undigested lactose remains in the gut;¹
• Lower in the intestines, some of the lactose will be broken down by bacterial enzymes. The by-products of this breakdown are organic acids and hydrogen. The organic acids, together with water (which is drawn from the intestine due to the increased osmotic pressure caused by the excess lactose) result in the symptoms of diarrhoea, abdominal pain, bloating and excess flatulence.¹ Perianal excoriation and vomiting may also occur.^2,3

Diagnosis

The standard medical test for the diagnosis of lactose intolerance is a hydrogen breath measurement. In this test, the person drinks a lactose-loaded beverage and the breath is analysed at regular intervals. Raised levels of hydrogen in the breath indicate improper digestion of lactose. This test is not performed on children younger than 6 months of age.

Treatment

It is important that people with lactose intolerance do not completely remove dairy foods from their diets as this puts them at increased risk of low bone mineral content and development of osteoporosis later in life.^4,5 Studies have shown that most adults with lactose intolerance can tolerate 12.5 grams of lactose per day (the amount of lactose found in a glass of milk).¹

It is crucial to remember that the extent of lactase deficiency can vary considerably from marginal to profound. Many people with symptomatic lactose intolerance will still be able to tolerate a reasonable amount of dairy foods, particularly the lower lactose forms such as cheese or yoghurt. People should be encouraged to conduct their own experiments by gradually increasing their intake of lactose-containing foods to determine their personal tolerance threshold.

When developing a management plan consider the following:

• Hard cheeses such as Cheddar, Colby and Swiss have virtually no lactose;
• Yoghurt is often well tolerated due to the presence of probiotic bacteria which partly pre-digest the lactose in the yoghurt. The texture of the yoghurt also slows down gastric emptying, reducing the amount of lactose entering the intestines at one time;
• Drinking small amounts of milk at regular intervals throughout the day can also be tolerated well and may have the benefit of building the level of lactose tolerance long-term. Full cream milk is often better tolerated than skim milk due to the effect of the fat on gastric emptying. If the lactose tolerance threshold is particularly low, consider using a lactose-free cow’s milk, a commercial lactase product (available from pharmacies) and/or supplements to replace nutrients from dairy foods.

Lactose content of dairy foods⁶

Health practitioners play a key role in helping their clients with lactose intolerance understand the importance of calcium and other dairy food nutrients in the diet, and the serious consequences of calcium deficiency. In developing meal plans for people with lactose intolerance, it is important to make sure that 3 serves of dairy foods are included each day. The following table lists the lactose and calcium content of common dairy foods.

Table: Lactose vs calcium content of various foods

* The lactose content in yoghurt decreases each day, even while it sits in the fridge, because the probiotic bacteria in it use lactose for energy.

References

1. Lomer MC, Parkes GC, Sanderson JD. Review article: lactose intolerance in clinical practice – myths and realities. Aliment Pharmacol Ther. 2008; 27(2): 93-103.
2. Joneja JV. Dietary Management of Food Allergies and Intolerances (2nd edition). Canada: JA Hall Publications; 1998.
3. Poskitt EM. Nutritional problems of preschool children. In: Sadler MJ, Strain JJ, Caballero M (eds). Encyclopedia of Human Nutrition. New York: Academic Press; 1999.
4. Di Stefano M, Veneto G, Malservisi S, Cecchetti L, Minguzzi L, Strocchi A, et al. Lactose malabsorption and intolerance and peak bone mass. Gastroenterology. 2002; 122(7): 1793-9.
5. Matlik L, Savaiano D, McCabe G, VanLoan M, Blue CL, Boushey CJ. Perceived milk intolerance is related to bone mineral content in 10- to 13-year-old female adolescents. Pediatrics. 2007; 120(3): e669-77.
6. Proximate Composition of Australian Dairy Foods. Melbourne: Australian Dairy Corporation; 1999.