Characteristics of Non-Lactose Dairy Intolerance: Based on Perceived and Actual Symptoms to Milk and Dairy Consumption Patterns

Abstract

Dairy intolerance is a prevalent food intolerance and is frequently attributed to lactose intolerance (LI). However, many studies identify a subgroup within self-diagnosed LI individuals that can digest lactose, yet still present with gastrointestinal symptoms following dairy consumption. Whether the perceived or experienced digestive symptoms in this non-lactose dairy intolerant (NLDI) subgroup differ from LI has not yet been investigated. This study aims to determine whether self-perceived intolerance symptoms differ between NLDI and LI and if these different intolerances actually experience these same symptoms with milk. Secondly, to investigate differences in dairy consumption between NLDI, LI and dairy tolerant (DT) subjects to infer dairy consumption patterns of NLDI. Perceived digestive responses to milk were first collected with a visual analogue scale (VAS) in a group of 40 healthy females (20-30 years) with different levels of self-reported dairy intolerance. LI subjects were separated from NLDI subjects with a 50 g lactose challenge. At a later visit, both groups consumed 750 mL milk and reported digestive discomfort using a VAS after 3 h. Perceived VAS symptom scores were compared between groups using one-way ANOVA analysis while actual VAS scores were compared using a generalised linear mixed model. Food frequency questionnaires and food symptom questionnaires were also completed by subjects focused on dairy product intake; Chi squared analyses were conducted to compare responses between subject groups. NLDI subjects had higher average perceived scores for abdominal distention, bloating, faecal urgency and flatulence compared to LI subjects (p<0.05); this was contrasted by reduced actual symptoms upon milk consumption. Actual VAS scores were instead higher in LI subjects for the same symptoms (p<0.05). Food frequency data revealed that the NLDI group are more likely to avoid ice cream, flavoured milk, hot beverages made with milk and milk as a drink. Further analysis showed that overall, NLDI are more likely to report more severe symptoms with these dairy products at a moderate to high frequency. Although NLDI subjects experienced greater perceived symptoms than LI, LI subjects still reported more severe symptoms following milk at 3 h. This confirms that some differences and similarities exist in symptom expression and severity between NLDI and LI subjects with milk, however further investigation is required to see if these findings can be replicated in a non-IBS population. Further investigation is also required on a larger scale to confirm the influence of digestive symptoms on the avoidance of dairy products in NLDI subjects in order to understand the underlying pathophysiology of the intolerance.