Dairy products in global public health

Intakes of dairy produce show enormous diversity between regions, cultures, and individuals around the world. At the geographic level, intake maps closely onto the distribution of lactase persistence (LP), a genetic trait that allows milk to be consumed beyond the weaning period without gastrointestinal side effects. The LP trait has been independently selected at least 4 times and is under rapid positive selection, which shows that dairy consumption has positive survival benefits. For people lacking the LP trait, the fermentation of milk into yogurt and related products (a process known for >= 8500 y) aids milk digestion through the breakdown of some lactose and the provision of beta-galactosidase, which remains active in the gastrointestinal tract. In global ecologic comparisons, milk and dairy intakes are strongly associated with adult height, and many international advisory bodies recommend the consumption of 400-500 mL milk equivalents/d. There are very few countries where such high intakes are met, and in populations in whom intakes are much lower there is evidence of adaptations that help to maintain bone health with surprisingly low intakes. Despite concerns that the high-saturated-fat content of full-fat dairy products would promote heart disease, recent meta-analyses show that dairy consumption is neutral or beneficial for weight control, coronary disease, diabetes, hypertension, and most cancers.