Drinking lots of milk may not lower the risk of fracturing bones, a study in the British Medical Journal suggests.
The research, conducted in Sweden, showed women who drank more than three glasses a day were actually more likely to break bones than those who had less.
View Reserach article here: Milk intake and risk of mortality and fractures in women and men: cohort studies
The researchers cautioned that their work only suggested a trend and should not be interpreted as proof that high milk consumption caused fractures. Factors such as alcohol and weight were likely to play a role, they said.
A team of scientists in Sweden examined the dietary habits of 61,400 women in 1987-1990 and 45,300 men in 1997 and then monitored their health for years afterwards. Participants were asked to complete questionnaires on how frequently they consumed common foods such as milk, yoghurt and cheese over a one-year period.
Researchers then tracked how many developed fractures and how many participants died in the years afterwards.
In the 20-year follow-up period in which the women were monitored, those who drank more than three glasses, or 680ml, of milk a day were more likely to develop fractures than those who had consumed less. The high-intake group had a higher risk of death too.
Prof Karl Michaelsson, lead researcher at Uppsala University, said: "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. And those who had a high milk intake also had a 50% higher risk of hip fracture."
Men were monitored for an average of 11 years after the initial survey and the results showed a similar but less pronounced trend
When fermented milk products such as yoghurt were considered, the opposite pattern was observed - people who consumed more had a lower risk of fractures.
Prof Michaelsson says the findings could be due to sugars in milk, which have been shown to accelerate ageing in some early animal studies
"The results should, however, be interpreted cautiously given the observational design of our study."
Dietary advice should not be changed until more research had been conducted, he said. British experts said the research should be treated with caution because the milk in Sweden is fortified with vitamin A which could have an impact on the findings.