A high intake of milk in the daily diet may be associated with a higher risk of death and bone fracture risk in women and higher mortality in men, according to Swedish researchers and published online October 28 in the BMJ.
They also warned to determine any dietary recommendations of this research for these results.
These studies were carried out at the University of Uppsala, Sweden. The researchers analysed data from two large Swedish cohorts: one with 61 433 women aged 39-74 years, and another with 45 339 men aged between 45 and 79 years old. By means of food frequency questionnaires, the researchers obtained data on food and beverages consumed on common daily and weekly basis.
The researchers write that a potential candidate for the different results for different types of dairy products is the content of D-galactose.
The intake of D-galactose from milk fermented is not significantly higher than that of other food sources, such as cheese and fermented milk products.
They cite animal studies that have provided a link between D-galactose and premature aging.
They analysed the results of enrolment (1987 to 1990 for women and for men in January 1998) until December 2010. During a median of 22 years follow-up, 15,541 women and 17,252 women died had a fracture. During a median 13-year follow-up, 10,112 men died and 5379 people have had a fracture.
The researchers found that women who drank three or more cups (680 grams) of milk per day had almost twice the risk of death compared with women who drank less than one drink per day. Women who drank more milk also had a higher risk for any fracture and for hip fracture in particular.
Although the researchers found that men who drank three or more glasses of milk had a slightly higher risk of death compared to those who drank less than one drink, the men did not have the excess risk of fractures than women.
The researchers recorded the calculations of risk factors for a wide range of co-factors, including but not limited to age, smoking habit, body mass index, height, level of education, level of calcium and vitamin D, without the use of cortisone, physical activity, and Charlson comorbidity index (the index of comorbidity currently the most used).
In a sensitivity analysis, adjusting the search for nutrients associated with osteoporosis or fracture risk, the researchers found a strong association between high consumption of milk and outcomes. They also found an association between high consumption of milk and oxidative stress and inflammation.
In contrast, the authors found no association between similar products fermented milk, including yogurt and cheese, and adverse outcomes.
The researchers did not make any distinction between the levels of fat in the milk, such as skim and whole, but all consumption of milk have been combined into a single category.
These results may question the validity of the recommendations of the high consumption of milk to prevent fragility fractures.