Milk is rich in 18 of the 22 essential nutrients in the body. Nutrition education has long promoted the important role of the combination of calcium and vitamin D in milk in maintaining bone health, especially during childhood development. The U.S. Department of Agriculture recommends three cups of dairy products per day to safeguard bone health and enhance bone mass. Some studies suggest that consuming 3 to 4 cups of milk per day can reduce osteoporosis-related medical expenditures by more than 20 percent. In addition, milk has been shown to have a variety of other benefits including: helping to maintain healthy blood pressure; reducing the risk of cardiovascular disease and type 2 diabetes; helping to prevent colorectal cancer; and providing natural high-quality protein for muscle synthesis and maintaining muscle mass. However, in this observational study conducted in Sweden by Professor KarlMichaëlsson et al. questioned some of the health benefits of milk, particularly the relationship between milk and long-term bone health, and the study reached conclusions that are inconsistent with conventional wisdom. Professor Michaëlsson et al. hypothesized that high milk consumption has the potential to increase oxidative stress, which may have an impact on mortality and fracture risk in subjects. This hypothesis is based on the fact that milk is the most important food source of dC galactose in humans and that galactose is present in milk as a structural part of lactose. Various experimental animal studies have confirmed that chronic exposure to dC galactose is detrimental to health, potentially leading to aging and reduced lifespan, by mechanisms that may include oxidative stress damage, chronic inflammation, neurodegeneration, decreased immune function, and gene transcription. To test this hypothesis, Professor Michaëlsson used two community-based cohorts to analyze the relationship between milk intake and mortality and fracture incidence. The Swedish Mammography cohort study, conducted between 1987 and 1990, included 61,433 female subjects aged 39C74 years. In contrast, a total of 61,433 male subjects aged 45C74 years were included in the Swedish Male Cohort Study conducted in 1997. Subjects were asked to complete a questionnaire reporting the average intake of 96 common foods and beverages, including milk, fermented milk, sour milk and cheese. In addition, Prof. Michaëlsson et al. collected information on the subjects’ lifestyle, weight and height, and included educational attainment and marital status in the analysis. Information on fractures and mortality in the subjects was queried using the Swedish medical registry system. During the 20-year follow-up period of the Swedish Mammography cohort study, 15,541 subjects died and 17,252 subjects had fractures, including 4,259 hip fractures. The analysis found no significant decrease in fracture risk with increasing milk intake. Furthermore, subjects who consumed >3 cups of milk per day (mean 680 ml) had an increased risk of death compared with subjects who consumed <1 cup of milk per day (mean 60 ml). During the 11-year follow-up period of the Swedish male cohort study, there were 10,112 deaths and 5,066 fractures, including 1,116 hip fractures. Analysis found that, although not as pronounced as in the female cohort, the risk of death increased in men with increased milk intake Further analysis of whether milk was associated with oxidative stress and inflammatory response revealed that milk intake was positively associated with oxidative stress and inflammatory response in subjects of both sexes. However, fermented milk, sour milk and cheese intake were negatively associated with indicators of oxidative stress and inflammatory response and positively associated with decreased mortality and fracture rates, and these associations were particularly pronounced in women. According to Professor Michaëlsson, our findings question the validity of the idea that heavy milk consumption prevents fragility fractures. Both for men and women, not only is there no significant reduction in fracture risk with increased milk intake, but it may also lead to increased mortality. The lactose and galactose content of milk may be associated with mortality and fracture risk in subjects, but the relationship between the two has yet to be confirmed. Professor Michaëlsson noted that the results should be interpreted with caution, considering that this study was only an observational study. The study only suggests a correlation and does not confirm a causal relationship. Therefore, further studies should be conducted before the results are applied to dietary recommendations. Commenting on the study, Mary Schooling of the City University of New York noted that because milk is so important in many dietary guidelines and because fractures and cardiovascular disease are relatively common among the elderly population, a revision of the evidence-based dietary recommendations could provide substantial benefit per case. On the other hand, milk intake is increasing with global economic development and increased consumption of food of animal origin, and there is an urgent need to clarify the role that milk plays in mortality.