Effects of High and Low Fat Dairy Food on Cardio-Metabolic Risk Factors: A Meta-Analysis of Randomized Studies

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. There was an increase in weight with low (+0.82, 0.35 to 1.28 kg, p<0.001) and whole fat dairy food (+0.41, 0.04 to 0.79kg, p=0.03), but no significant change in waist circumference (-0.07 , -1.24 to 1.10 cm) ; HOMA –IR (-0.94 , -1.93 to 0.04 units); fasting glucose (+1.32 , 0.19 to 2.45 mg/dl) ; LDL-c (1.85 ,-2.89 to 6.60 mg/dl); HDL-c (-0.19 , -2.10 to 1.71 mg/dl); systolic BP (-0.4, -1.6 to 0.8 mmHg); diastolic BP (-0.4 , -1.7 to 0.8 mmHg) or CRP (-1.07 , -2.54 to 0.39 mg/L). Changes in other cardio-metabolic risk factors were similar for low 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