Kirsty M Turner, Jennifer B Keogh, and Peter M Clifton

Conclusion: In contrast to some epidemiologic findings, these results suggest that high consumption of dairy reduces insulin sensitivity compared with a diet high in lean red meat in overweight and obese subjects, some of whom had glucose intolerance.

Background: Epidemiologic studies have linked high consumption of red and processed meat with risk of developing type 2 diabetes, whereas high dairy consumption has been associated with decreased risk, but interventions have been limited.

Objective: We compared the effects on insulin sensitivity of consuming a diet high in lean red meat with minimal dairy, a diet high in dairy primarily low fat (from milk, yogurt, or custard) with no red meat, and a control diet that contained neither red meat nor dairy.

Design: A randomized crossover study was undertaken with 47 overweight and obese men and women divided into 2 groups as follows: those with normal glucose tolerance and those with impaired fasting glucose or impaired glucose tolerance. Participants followed the 3 weight-stable dietary interventions for 4 wk with glucose, insulin, and C-peptide measured by using oral-glucose-tolerance tests at the end of each diet.

Results: Fasting insulin was significantly higher after the dairy diet than after the red meat diet (P < 0.01) with no change in fasting glucose resulting in a decrease in insulin sensitivity after the high-dairy diet (P < 0.05) as assessed by homeostasis model assessment of insulin resistance (HOMA-IR). A significant interaction between diet and sex was observed such that, in women alone, HOMA-IR was significantly lower after the red meat diet compared with dairy diet (1.33 ± 0.8 compared with 1.71 ± 0.8, respectively; P < 0.01). Insulin sensitivity calculated by using the Matsuda method was 14.7% lower in women after the dairy diet compared with red meat diet (P < 0.01) with no difference between diets in men. C-peptide was not different between diets.