From 'lactose intolerance' to 'lactose nutrition'

Area of Science:

• Nutritional Science
• Human Genetics
• Microbiology

Background:

• Lactose intolerance is widely recognized but often misconstrued as a disorder.
• Lactase persistence (LP) is genetically determined, linked to specific single nucleotide polymorphisms (SNPs) like C/T-13910 in the MCM6 gene, enabling lifelong lactase activity, primarily in European-derived populations.
• Other LP populations exist in Africa and the Middle East with distinct genetic variants, reflecting co-evolution with dairying.

Purpose of the Study:

• To re-evaluate the concept of lactose intolerance and its relationship with lactase non-persistence (LNP).
• To investigate the factors influencing gastrointestinal symptoms attributed to lactose malabsorption.
• To propose a shift from lactose tolerance tests to dairy food tolerance tests.

Main Methods:

• Review of existing evidence on lactase persistence, genetics, and lactose malabsorption.
• Analysis of the correlation between gastrointestinal symptoms and lactase non-persistence.
• Consideration of the role of the colonic microbiome and dietary factors in lactose digestion.

Main Results:

• Gastrointestinal symptoms are poorly correlated with lactase non-persistence (LNP), affecting the majority of the global population.
• Lactose fermentation by the colonic microbiome in LNP individuals produces short-chain fatty acids and gases, with symptom onset being dose-dependent.
• Up to 25g of lactose can often be tolerated by LNP individuals, influenced by food context, microbiome, and age.

Conclusions:

• The concept of lactose intolerance as a disorder in LNP individuals is a misplaced cultural perspective.
• Symptom manifestation is dependent on the specific dairy product consumed and individual tolerance factors, not solely on LNP status.
• Dairy food tolerance tests are recommended as a more accurate assessment than traditional lactose tolerance tests.