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Are you getting enough dairy? Maybe it’s time you did.

Nov. 11, 2011

By Maria Serraino

Dairy foods may improve bone health during diet and exercise in overweight premenopausal women.

A study in The Endocrine Society’s Journal of Clinical Endocrinology and Metabolism (JCEM) found that bone loss that is often associated with calorie-restricted diets may be reversed after consuming protein and calcium from dairy sources. Completed by researchers at McMaster University, the study found that consumption of dairy foods and higher protein resulted in improvements in markers of bone formation and reductions in markers of bone degradation. 

The study, which focused on Improving Diet Exercise and Lifestyle (IDEAL) for women study, involved a controlled randomized weight loss intervention trial designed to help women lose weight while supporting bone health. The trial involved 90 premenopausal overweight or obese women between the ages of 19 and 45, who were otherwise healthy, low dairy consumers (consuming no more than one serving of dairy per day), generally sedentary, regularly menstruating, not pregnant or nursing and not taking any vitamin or mineral supplements. 

The study randomly assigned participants to one of three groups: high protein and high dairy (HPHD), adequate protein and medium dairy (APMD), and adequate protein and low dairy (APLD). The groups differed in the amount and type of protein consumed: the APLD group maintained stable dairy intakes of zero to one serving per day and 15 per cent of their daily energy from nondairy sources of protein; the APMD group had three to four servings of dairy per day and consumed 15 per cent of their daily energy from protein; and the HPHD group had six to seven servings of dairy per day and consumed 30 per cent of their daily energy from high quality protein. All of the participants received individualized counselling by dietitians and nutritionists and underwent the same exercise and training. 

The study found that despite equivalent weight loss across all groups, the HPHD group experienced greater total fat loss, visceral fat loss and lean mass gains. Dietary protein consumption increased in the HPHD group, and dietary calcium and vitamin D intake increased in the HPHD and APMD groups and decreased in the APLD group. There were no significant changes in any group in bone mineral density. Both the APMD and HPHD groups showed significant reductions in parathyroid hormones (associated with increasing bone degradation), whereas the APLD group showed a significant increase. In terms of markers of bone formation, examined through testing OC, BSAP and P1NP, OC increased in HPHD and APLD and was unchanged in APMD, BSAP was unchanged in all groups, and P1NP increased significantly in HPHD and APMD and was unchanged in APLD. The researchers also looked at two markers of bone degradation, and found that both increased significantly in the APLD group, with the increases being greater than those in APMD and HPHD groups. 

The results of the study show that consumption of dairy foods and higher protein resulted in improved markers of bone health and calcium metabolism in overweight and obese young women who are involved in a weight loss program. The researchers found positive changes in bone health in the HPHD group and in the APMD group. The changes observed spanned a variety of bone-related processes including bone matrix turnover, bone collagen turnover, and osteoclast differentiation. These processes all changed in a manner that suggests that higher dairy food and calcium consumption during diet- and exercise-induced weight loss augments new bone formation. In general, changes in bone markers in the APLD group were in the opposite direction and were indicative of increases in bone resorption, reduced bone collagen formation and increased osteoclast activity.  

The researchers recommend consumption of dairy foods to help with weight loss, as it also promotes bone health in young women.  

The study will appear in the January 2012 issue of JCEM.

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  • A publication of:
  • Women's College Hospital