Lactose intolerance refers to the body’s decreased ability to digest the milk sugar lactose as a result of low lactase enzyme levels. Lactose intolerance does not mean that dairy products should be avoided. Indeed, there are dietary strategies that effectively alleviate symptoms, while enabling the daily consumption of milk and milk products.
Symptoms and prevalence
If lactose is not broken down by lactase, it can cause symptoms such as bloating, flatulence or, in severe cases, osmotic diarrhea. All infants produce lactase and are able to digest lactose. However, after weaning, a genetically programmed decrease in lactase (lactase non-persistence) occurs in most children worldwide,1 and approximately 70% of the world’s population has a lactase deficiency at some point in their life. The prevalence of lactose intolerance varies greatly between populations, from less than 5% in Swedish adults to 80-90% in the Japanese population.2,3
Avoiding dairy products when lactose intolerant is generally unnecessary and can have a detrimental effect on the intake of essential nutrients such as calcium and B-vitamins. Available evidence suggests that lactose intolerant adults and adolescents can consume a single dose of at least 12-15 g of lactose (equivalent to the lactose content of one cup of milk) and experience little or no symptoms. A 24 gram dose, divided over the course of a day has also been found to be generally well-tolerated.1,4
Some dairy products are also better tolerated than others. Yoghurt and hard cheeses represent particularly good choices for lactose intolerant persons. Indeed, yoghurt bacteria partially digest the lactose into glucose and galactose, and the semisolid state slows gastric emptying and gastrointestinal transit, producing fewer symptoms. Due to their production and maturation process, hard cheeses contain virtually no lactose, while maintaining an excellent level of many nutrients.
- Suchy FJ, Brannon PM, Carpenter TO et al. National Institutes of Health Consensus Development Conference: lactose intolerance and health. Ann Intern Med;152:792-6.
- Schaafsma G (2008). International Diary Journal, 18: 458-465
- Heyman MB (2006). Lactose intolerance in infants, children, and adolescents. Pediatrics;118:1279-86.
- Wilt TJ, Shaukat A, Shamliyan T, et al. Lactose intolerance and health. Evid Rep Technol Assess (Full Rep):1-410