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. 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.