We've been brought up to think that drinking milk is good for our bones, but new research suggests that not only is this false, but the sugars in it may actually be accelerating the ageing process.
A research team from Uppsala University in Sweden has found that women who drink more than three glasses of milk per day were more likely to break their bones than women who drank less.
This finding was part of a study conducted on more than 100,000 people in Sweden, based on how much dairy they habitually consumed. The researchers monitored the diets of 61,400 women between 1987 and 1990 and 45,300 men through 1997 by asking them to fill out questionaries on how often they ate common dairy products such as milk, cheese, and yoghurt. The health of the female participants was monitored for 20 years after the questionnaires, and for 11 years afterwards for the males.
Publishing their results in the BMJ, the team says that in women, high milk intake led to a greater risk of bone fracture, and in both men and women, it was associated with a higher mortality rate.
"Women who drank three or more glasses a day had twice the chance of dying at the end of the study than those who drank less than one glass a day," lead researcher Karl Michaelsson, a professor in medical epidemiology at Uppsala University, told BBC News. "And those who had a high milk intake also had a 50 percent higher risk of hip fracture."
Interestingly, unlike milk, when the dairy product was fermented, like in yoghurt, the results were reversed. The participants who consumed more yoghurt showed a decreased risk of experiencing bone fractures. Michaelsson told BBC News that the difference could be down to the sugars that are found in milk - lactose and galactose. Both have been shown to accelerate ageing processes such as inflammation and oxidative stress in previous research using animals.
While the study involved a good amount of participants and was conducted over a relatively long period of time, the researchers are careful to point out that they're not ready to draw causal conclusions just yet. Something they want to look at in the future is if alcohol consumption and weight could have had an effect on the results.
"As milk features in many dietary guidelines and both hip fractures and cardiovascular disease are relatively common among older people, improving the evidence base for dietary recommendations could have substantial benefits for everyone," epidemiologist Mary Schooling from the City University of New York in the US, wrote in an accompanying editorial in the BMJ.
Source: BBC News