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Back to Symposium 2018

Demystifying Lactose Intolerance

Susan I. Barr Susan I. Barr, PhD, FDC

Professor Emeritus of Nutrition
The University of British Columbia

Lactose intolerance -- real or perceived -- is a potential health concern: it can lead to avoidance of milk products and thus lower intakes of key nutrients such as calcium and vitamin D, which have potential implications for health. According to a nationally representative study, 16% of Canadians 19 years and older perceive themselves to be lactose intolerant. This study also revealed that those who perceive themselves to be lactose intolerant consumed less calcium than those who did not, despite a higher intake of calcium supplements. The use of fortified beverages was very low and did not make a substantive contribution to calcium intakes.

Lactose intolerance can be clinically diagnosed by administering an oral lactose load and monitoring breath hydrogen levels (which increase in those who maldigest lactose) and the occurrence of symptoms (abdominal pain, bloating, gas, diarrhea). However, most people who identify as lactose intolerant have not been clinically diagnosed; instead, they diagnose themselves or their diagnosis is based on self-reported symptoms. Research indicates that many of those who believe they are lactose intolerant digest lactose completely.

Unlike milk allergy, those who are lactose intolerant do not need to exclude milk products from their diets.  Numerous double-blind studies confirm that almost all individuals with severe self-reported lactose intolerance can consume ~12-15 grams of lactose at a time (240 ml milk = ~12 g lactose) without noticeable symptoms. However, other strategies may be useful for those who believe they are severely lactose intolerant and/or choose not to consume milk. These include using dairy products with less lactose (e.g., hard cheese, yogurt), using smaller portions, and/or using fortified non-dairy alternatives. Health professionals should work closely with clients to ensure a “food first approach” and that dairy products are not needlessly avoided; however, in some cases, supplementation may be required to achieve recommended calcium and vitamin D intakes. Sensitivity is needed when working with people who believe they are lactose intolerant.

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