Effects of high and low fat dairy food on cardio-metabolic risk factors: a meta-analysis of randomized studies.

Abstract

IMPORTANCE: Clear guidelines on the health effects of dairy food are important given the high prevalence of obesity, cardiovascular disease and diabetes, and increasing global consumption of dairy food. OBJECTIVE: To evaluate the effects of increased dairy food on cardio metabolic risk factors. DATA SOURCES: Searches were performed until April 2013 using MEDLINE, Science Direct, Google,Embase, the Cochrane Central Register of Controlled Trials, reference lists of articles, and proceedings of major meetings. STUDY SELECTION: Randomized controlled studies with healthy adults randomized to increased dairy food for more than one month without additional interventions. DATA EXTRACTION AND SYNTHESIS: A standard list was used to extract descriptive, methodological and key variables from all eligible studies. If data was not included in the published report corresponding authors were contacted. RESULTS: 20 studies with 1677 participants with a median duration of dietary change of 26 (IQR 10-39) weeks and mean increase in dairy food intake of 3.6 (SD 0.92) serves/day were included. Increased dairy food intake was associated with a modest weight gain (+0.59, 95% confidence interval 0.34 to 0.84kg, p<0.0001) but no significant change in waist circumference (0.35 , -0.75 to 1.45 cm); insulin resistance (HOMA –IR -0.94 , -1.93 to 0.05 units); fasting glucose (0.87, -0.27 to 2.01 mg/dl); LDL-cholesterol (1.36 ,-2.38 to 5.09 mg/dl); HDL-cholesterol (0.45, -2.13 to 3.04 mg/dl); systolic (-0.13, -1.73 to 1.98 mmHg) and diastolic blood pressure (0.13, -1.73 to 1.98 mmHg) or C-reactive protein (-0.08, -0.63 to 0.48 mg/L). Results were similar for studies with low-fat and whole-fat dairy interventions. LIMITATIONS: Most clinical trials were small and of modest quality. . CONCLUSION: Increasing whole fat and low fat dairy food consumption increases weight but has minor effects on other cardio-metabolic risk factors. TRIAL REGISTRATION ACTRN: Australian New Zealand Clinical Trials Registry ACTRN12613000401752, http://www.anzctr.org.au. ETHICS APPROVAL NUMBER: NTX/10/11/115.