Researchers in Sweden examined whether or not consuming milk in high amounts can lead to higher levels of oxidative stress, which then results into increased risks of fractures and even death.
Led by Karl Michaelsson, the researchers analyzed information from two large groups of men and women who filled out food frequency questionnaires about 96 common food items, including milk, cheese, and yogurt. Height, weight, and other lifestyle data were collected for the study, as well as other factors like marital status and education level. To keep track of fracture rates and deaths, national registers were used.
For the 20 years that 61,433 women were tracked, 17,252 experienced at least one fracture (4,259 of the cases were for hip fractures) while 15,541 died. For this group, there was no reduction in risks for fractures when higher milk consumption was involved. In fact, drinking more than three glasses of milk in a day led to higher risks of death in women compared to those who drank less than a glass of milk per day.
For the men, tracking was carried out for 11 years. During that time, 5,066 had fractures (1,166 of which are hip fractures) and 5,066 of the 45,339 men died. Like the women, the men also had higher risks of death when higher milk consumption is factored in, although their risks were less pronounced than the women.
This really does make people think twice about drinking milk but it's important to note that risks for fractures and deaths are not the same for all dairy products. Where milk may have led to a higher rate of fractures and deaths in the groups, consuming fermented milk products like cheese and yogurt was associated with a reduction in the risks, most especially in women.
According to the researchers, the results of their study may question how valid current recommendations are for milk consumption, of which high levels tout bone protection.
"The results should, however, be interpreted cautiously given the observational design of our study. The findings merit independent replication before they can be used for dietary recommendations," they wrote.
Mary Schooling, a professor at the City University if New York, said the study highlights a fascinating angle about milk but stresses that diets are difficult to precisely assess so the findings must be interpreted with caution. Milk consumption will rise all over the world as economic developments increase, as well as the consumption of animal products. The role of milk in relation to mortality must be defined now, she added.