Acute caffeine ingestion reduces insulin sensitivity in healthy subjects: a systematic review and meta-analysis
What this study found
Acute caffeine ingestion reduced insulin sensitivity in healthy subjects. Across trials, the pooled insulin sensitivity index was lower with caffeine versus placebo or control (SMD -2.06, 95% CI -2.67 to -1.44; I2 = 49%; P for heterogeneity = 0.07). The authors concluded that short-term caffeine exposure may shift glycemic homeostasis toward hyperglycemia and that longer-term trials are needed to understand chronic effects and coffee's potential anti-diabetic role.
- Study & population
- Systematic review and meta-analysis of 7 randomized controlled trials involving 70 healthy adults without diabetes.
- Intervention
- This systematic review evaluated acute caffeine exposure, most often as single oral doses of 4.45 to 6 mg/kg or 5 mg/kg, with one intravenous dose of 3 mg/kg and one caffeinated coffee condition.
- Key limitation
- The evidence base was small, with only 7 short-term trials and 70 participants total.
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Open PDFOriginal abstract
BackgroundAccording to previous meta-analyses, coffee consumption reduces the risk of type 2 diabetes mellitus. However, the underlying mechanism remains unknown. Whether caffeine, the key ingredient in coffee, has a beneficial effect on the glycemic homeostasis and the anti-diabetic effect is particularly controversial. The aim of this study was to summarize the effect of acute caffeine ingestion on insulin sensitivity in healthy men.MethodsA comprehensive literature search for papers published before April 2016 was conducted in EMBASE, PubMed, and Cochrane Library databases. Randomized controlled trials (RCTs) that investigated the effect of caffeine on insulin sensitivity in healthy humans without diabetes were included. A random effects meta-analysis was conducted using Review Manager 5.3.ResultsThe search yielded 7 RCTs in which caffeine intake was the single variant. Compared with placebo, caffeine intake significantly decreased the insulin sensitivity index, with a standardized mean difference of −2.06 (95% confidence interval −2.67 to −1.44, I2 = 49%, P for heterogeneity = 0.06).ConclusionAcute caffeine ingestion reduces insulin sensitivity in healthy subjects. Thus, in the short term, caffeine might shift glycemic homeostasis toward hyperglycemia. Long-term trials investigating the role of caffeine in the anti-diabetic effect of coffee are needed.