Lactose intolerance and other related food sensitivities

Milk and dairy food consumption can lead to a range of adverse clinical symptoms, the best known of which is lactose intolerance (LI). LI is defined as experiencing gastrointestinal symptoms following the ingestion of lactose. While LI is often caused by a genetically determined reduction of lactase production in adulthood, it is important to note that other causes exist. In addition, adverse gastrointestinal and other symptoms following milk and dairy food consumption may not necessarily be the result of LI. Despite our deeper understanding of food sensitivities and their overlap with irritable bowel syndrome, misattribution of gastrointestinal symptoms to lactose ingestion in self-reporting lactose-intolerant individuals remains common. In this chapter we discuss the complexities of lactose-related and lactose-independent adverse gastrointestinal and other symptoms associated with milk and dairy food consumption as well as the nutritional consequences of dairy food avoidance