Effect of low-ratio n-6/n-3 PUFA on blood glucose: a Meta-analysis
Objective The aim of this meta-analysis was to investigate the effect of increasing dietary low-ratio n-6/n-3 polyunsaturated fatty acid (PUFA) intake on blood glucose and other related indicators. Methods We systematically searched randomized controlled trials of low-ratio n-6/n-3 PUFA intervention on PubMed, Embase, Cochrane library and related references up to August 2018. The change values were calculated as weighted mean difference (WMD) by using a random-effect model. Results Eleven randomized controlled trials were included. No significant effect of dietary low-ratio n-6/n-3 PUFA supplementation was observed on fasting blood glucose (WMD: 0.057 mmol/L; 95% CI: -0.090 to 0.204 mmol/L), insulin (WMD: -0.757 mIU/L; 95% CI: -2.419 to 0.904 mIU/L), insulin resistance index (WMD: -0.201; 95% CI: -0.566 to 0.165), and glycosylated hemoglobin (WMD: -0.063%; 95% CI: −0.061 to 0.186%). Subgroup analysis showed that the effect of low-ratio n-6/n-3 PUFA on the reduction of plasma insulin level in North America (WMD: -3.473 mIU/L; 95% CI: -5.760 to -1.185 mIU/L) was more obvious than that in Asian countries (WMD: −0.797 mIU/L; 95% CI: −2.497 to 0.902 mIU/L) and European countries (WMD: −0.063 mIU/L; 95% CI: −0.061 to 0.186 mIU/L). In the subgroup of diabetic subjects, low-ratio n-6/n-3 PUFA supplementation can decrease plasma insulin level (WMD: −3.010 mIU/L; 95% CI: −5.371 to -0.648 mIU/L) and insulin resistance index (WMD: −0.460; 95% CI: −0.908 to -0.012). When invention period was longer than 8 weeks, low-ratio n-6/n-3 PUFA supplementation could also decrease plasma insulin level (WMD: −2.782 mIU/L; 95% CI: −4.946 to -0.618 mIU/L). No significant publication bias was observed for all blood glucose and other related indicators as suggested by Begg’s test and Egger’s test. Conclusion Our meta-analysis found low-ratio n-6/n-3 PUFA supplementation could improve the glucose metabolism by reducing the insulin and insulin resistance in the diabetic patients. Low-ratio n-6/n-3 PUFA supplementation could reduce plasma insulin level when supplementation duration was longer than 8 weeks.