Lactose and type 2 diabetes: Nutritional and metabolic perspectives

Diabetes mellitus, particularly type 2 diabetes (T2D), is one of the most prevalent metabolic disorders worldwide, strongly influenced by lifestyle and nutritional factors. Current dietary recommendations emphasize the importance of carbohydrate quality and food matrix effects in modulating glycaemic control and insulin sensitivity. Lactose, the principal disaccharide in milk, is frequently overlooked in the context of diabetes research, as most attention has been focused on other dietary sugars such as glucose, sucrose, and fructose. However, lactose displays a relatively low glycaemic index compared to other carbohydrates and is hydrolysed into glucose and galactose, the latter showing potential antioxidative and anti-inflammatory effects. Moreover, a growing body of evidence suggests that dairy intake is associated with a reduced risk of type 2 diabetes, with fermented dairy products, such as yogurt and kefir, consistently showing the most protective associations. Recent studies have further highlighted the role of genetic variation in lactase persistence and non-persistence, pointing to the potential influence of gut microbiota and lactose fermentation products on glucose homeostasis. The aim of this review is to provide an overview of current evidence linking lactose metabolism and dairy consumption to the risk, regulation, and management of type 2 diabetes.