April Flowers for redOrbit.com – Your Universe Online
How many times were you told as a child that drinking your milk would give you strong bones? Turns out that might not be true.
A new study led by Uppsala University and published in The British Medical Journal reveals that drinking more milk not only doesn’t lower your risk of fractures, it might raise your risk of death.
The research team, which included members from Karolinska Institute and Uppsala University, believes their findings might be explained by the high levels of lactose and galactose (types of sugar) in milk. These sugars have been shown to increase oxidative stress and chronic inflammation in animal studies.
They caution, however, that their results can only show an association, not prove cause and effect. They recommend further studies before any firm conclusions or dietary recommendations can be made.
“A diet rich in milk products is promoted to reduce the likelihood of osteoporotic fractures,” writes Emma Dickinson for the British Medical Journal. “But previous research looking at the importance of milk for the prevention of fractures and the influence on mortality rates show conflicting results.”
The new study, led by Uppsala University’s Professor of Surgical Sciences Karl Michaëlsson, investigated whether oxidative stress, which affects the risk of mortality and fracture, would increase due to a high milk intake.
Food frequency questionnaires for 96 common foods — including milk, yogurt and cheese — were completed by two large groups of participants in Sweden. The first group included 61,433 women between the ages of 39-74 years in 1987-1990. The second group was made up of 45,339 men between the ages of 45-79 in 1997.
The researchers also collected lifestyle data, weight, height and factors such as education level and marital status. Fracture and mortality rates were tracked through the National registers.
The female group was tracked for an average of 20 years. During this period, 15,541 died and 17,252 suffered a fracture — 4,259 of those fractures were hip fractures. The researchers found no reduction in fracture risk for the women with higher milk consumption. In fact, women who drank more than three glasses of milk a day (average of 23 oz) had a higher risk of death than women who drank one glass of milk a day (average of 2 oz).
The male participants were tracked for an average of 11 years. During this time, 10,112 men died and 5,066 suffered fractures. Of those fractures, 1,166 were hip fractures. The risk of death was also higher in men who consumed large quantities of milk, but not as pronounced a difference as with women.
The research team was able to identify a positive association between milk intake and the biomarkers of oxidative stress and inflammation. Strangely, they found an association with reduced rates of mortality and fracture (especially in women) and a high intake of fermented milk products with low lactose content, such as yogurt and cheese.
“Our results may question the validity of recommendations to consume high amounts of milk to prevent fragility fractures,” they write. “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.”
Professor Mary Schooling at City University of New York said in an accompanying editorial that the new study raises a fascinating possibility about the potential harms of milk. She stresses, however, that assessing diet precisely is difficult.
“As milk consumption may rise globally with economic development and increasing consumption of animal source foods, the role of milk and mortality needs to be established definitively now,” she concluded.
Related Reading:
> Ancient Europeans Were Lactose Intolerant For Thousands Of Years
> Study Re-examines The Evolutionary Origins Of Lactose Tolerance
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