Milk intake may protect against type 2 diabetes in patients with lactose intolerance: Study

Patients with lactose intolerance are usually advised not to consume milk. However, many still consume dairy products despite experiencing gastrointestinal symptoms. The American study showed that surprisingly, this "unreasonable" strategy may have the benefit of reducing the risk for type 2 diabetes (T2D). 

Lactase non-persistence is an autosomal recessive trait that leads to the down-regulation of lactase activity in the intestinal mucosa and lactose maldigestion. Lactose is present in milk and dairy products; it is a saccharide hydrolysed by the enzyme lactase-phlorizin hydrolase to glucose and galactose in the brush border of the small intestine. 

Cow’s milk is frequently included in the human diet. Nutritional studies have repeatedly studied the effect of milk consumption on diabetes, among other factors, with sometimes heterogeneous results in different countries. The reason for this is presumed to be that in Asia, most people — 60%-100% — are lactose intolerant, whereas in Europe, only as much as 40% of the population has lactose intolerance.

In their paper, the authors led by Kai Luo, Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY, USA, did not mention lactose tolerance and intolerance. Instead, they divided the study population into lactase-persistent and non-lactase-persistent participants.

The authors, using data from the Hispanic Community Health Study/Study of Latinos, revealed that in both sexes, higher milk consumption is associated with lower T2D risk in lactase non-persistent individuals (determined by a variant of the lactase LCT gene, single nucleotide polymorphism rs4988235) but not in lactase persistent individuals.

The researchers validated this finding in the UK Biobank. Further analyses showed that among LNP individuals, higher milk consumption is associated with alterations in circulating metabolites (for example, reduced branched-chain amino acid metabolites and increased indole propionate) and gut microbiota (for example, enriched Bifidobacterium and reduced Prevotella).

Many of these metabolites are related to the identified milk-associated bacteria and partially mediate the association between milk intake and type 2 diabetes in LNP individuals.

"Not being lactase-persistent does not necessarily exclude the ability to consume a certain amount of lactose," said Lonneke Janssen Duijghuijsen, PhD, a nutrition scientist at Wageningen University, Wageningen, the Netherlands.

"Studies have shown that many individuals who lack lactase can still consume up to 12 g of lactose per day — equivalent to the amount in a large glass of milk — without experiencing intolerance symptoms."

Reference:

Luo, K., Chen, G., Zhang, Y., Moon, J., Xing, J., Peters, B. A., Usyk, M., Wang, Z., Hu, G., Li, J., Selvin, E., Rebholz, C. M., Wang, T., Isasi, C. R., Yu, B., Knight, R., Boerwinkle, E., Burk, R. D., Kaplan, R. C., . . . Qi, Q. (2023). Variant of the lactase LCT gene explains association between milk intake and incident type 2 diabetes. Nature Metabolism, 6(1), 169-186. https://doi.org/10.1038/s42255-023-00961-1