Mediterranean Diet Associated With Reduced Hip Fracture in Postmenopausal Women

EBM Focus - Volume 11, Issue 14

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Reference - JAMA Intern Med 2016 Mar 28 early online (level 2 [mid-level] evidence)

  • While the effects of dietary supplements on preventing fractures been inconsistent, improvements to overall diet may prevent nutrient deficiencies and improve bone health.
  • A recent analysis of the Women’s Health Initiative study including 90,014 postmenopausal women assessed 4 different dietary patterns and found a small reduction in the risk of hip fracture in women with high adherence to the Mediterranean diet.
  • Several additional factors, including changes in diet and physical activity over time, may influenced the results of this study, but suggest that a high adherence to the Mediterranean diet together with an overall healthy lifestyle may help protect against hip fracture.

Hip fractures are a major source of morbidity and mortality for elderly patients, especially women. Vitamins and mineral supplements such as calcium and vitamin D have been reported to reduce osteoporosis and fractures in postmenopausal women, but the evidence is inconsistent (BMJ 2011 May 24;342:d1473, N Engl J Med 2006 Feb 16;354(7):669). Women with deficiencies in these individual nutrients are more likely to have a lower quality diet; therefore, focusing on a healthier overall diet may be more effective for preventing osteoporotic fracture than providing individual supplements. To further assess the role of diet in fracture prevention, a recent post-hoc analysis of the Women’s Health Initiative study evaluated 4 dietary patterns in 90,014 postmenopausal women.

Women completed food frequency questionnaires at baseline that were scored for extent of adherence to each of 4 dietary patterns: Mediterranean diet, Healthy Eating Index 2010, Alternate Healthy Eating Index 2010, and Dietary Approaches to Stop Hypertension [DASH] diet. During a median of 15.9 years of follow-up, 2,121 hip fractures and 28,718 total fractures were reported. Women with scores representing the lowest quintiles of adherence to each diet were compared to women with adherence scores in all other quintiles. These analyses were adjusted for potential confounders such as age, history of fractures, and physical activity. Comparing lowest vs. highest quintiles, the highest quintile of adherence to the Mediterranean diet was associated with a significant reduction in the risk of hip fracture (adjusted hazard ratio 0.8, 95% CI 0.66-0.97). The highest quintile of adherence to Healthy Eating Index 2010 and the DASH diet were associated with nonsignificant decreases in the risk of hip fracture compared to the lowest quintiles. However, there were no significant differences in risk of total fracture with increased adherence to any of the 4 dietary patterns. A subgroup analysis of 7,961 women who had bone mineral density analyses at baseline and 6 years also found no significant differences in bone mineral density or lean body mass with adherence to any dietary pattern.

The results of this study suggest that the Mediterranean diet may decrease the risk of hip fracture, but the absolute decrease in risk was small. Two aspects of this study suggest that the effect of the Mediterranean diet may be underestimated. First, adherence to the Mediterranean diet was lower in this population than in previous cohorts reporting the benefits of the Mediterranean diet (BMJ 2005 Apr 30;330(7498):991). This low adherence may in part explain the small absolute decrease in risk. Second, this study included healthy postmenopausal women with a lower incidence of hip fracture than previously reported for U.S. women as a whole (Osteoporos Int 2012 Sep;23(9):2239), which may lead to a further underestimation of the protective effect of the diet. On the contrary, a healthier diet may also go hand in hand with an overall healthier lifestyle, which could lead to overestimation of the effect of diet alone. While the analysis of fracture risk was adjusted for baseline differences in clinical and demographic factors including chronic medical conditions and physical activity, many of these factors as well as diet itself are not constant. These factors may change considerably over the long follow-up duration, and this analysis did not adjust for changes over time. Overall, the results of this study suggest that healthy dietary patterns may contribute to fracture prevention as part of a healthy and active lifestyle.

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