Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
Nutritional Sciences Program, School of Public Health, University of Washington, Seattle, WA, USA.
Am J Clin Nutr. 2021 Mar 11;113(3):534-547. doi: 10.1093/ajcn/nqaa301.
Dairy foods, particularly yogurt, and plasma biomarkers of dairy fat intake are consistently inversely associated with incident type 2 diabetes. Yet, few trials assessing the impact of dairy on glucose homeostasis include fermented or full-fat dairy foods.
We aimed to compare the effects of diets rich in low-fat or full-fat milk, yogurt, and cheese on glucose tolerance and its determinants, with those of a limited dairy diet.
In this parallel-design randomized controlled trial, 72 participants with metabolic syndrome completed a 4-wk wash-in period, limiting dairy intake to ≤3 servings/wk of nonfat milk. Participants were then randomly assigned to either continue the limited dairy diet, or switch to a diet containing 3.3 servings/d of either low-fat or full-fat dairy for 12 wk. Outcome measures included glucose tolerance (area under the curve glucose during an oral-glucose-tolerance test), insulin sensitivity, pancreatic β-cell function, systemic inflammation, liver-fat content, and body weight and composition.
In the per-protocol analysis (n = 67), we observed no intervention effect on glucose tolerance (P = 0.340). Both the low-fat and full-fat dairy diets decreased the Matsuda insulin sensitivity index (ISI) (means ± SDs -0.47 ± 1.07 and -0.25 ± 0.91, respectively) and as compared with the limited dairy group (0.00 ± 0.92) (P = 0.012 overall). Body weight also changed differentially (P = 0.006 overall), increasing on full-fat dairy (+1.0 kg; -0.2, 1.8 kg) compared with the limited dairy diet (-0.4 kg; -2.5, 0.7 kg), whereas the low-fat dairy diet (+0.3 kg; -1.1, 1.9 kg) was not significantly different from the other interventions. Intervention effects on the Matsuda ISI remained after adjusting for changes in adiposity. No intervention effects were detected for liver fat content or systemic inflammation. Findings in intent-to-treat analyses (n = 72) were consistent.
Contrary to our hypothesis, neither dairy diet improved glucose tolerance in individuals with metabolic syndrome. Both dairy diets decreased insulin sensitivity through mechanisms largely unrelated to changes in key determinants of insulin sensitivity.This trial was registered at clinicaltrials.gov as NCT02663544.
乳制品，尤其是酸奶，以及反映乳制品脂肪摄入的血浆生物标志物，与 2 型糖尿病的发生呈负相关。然而，评估乳制品对葡萄糖稳态影响的试验很少包含发酵或全脂乳制品。
我们旨在比较富含低脂或全脂牛奶、酸奶和奶酪的饮食与限制乳制品饮食对葡萄糖耐量及其决定因素的影响。
在这项平行设计的随机对照试验中，72 名代谢综合征患者完成了 4 周的洗脱期，将乳制品摄入量限制在每周≤3 份脱脂牛奶。然后，患者被随机分配继续限制乳制品饮食，或在 12 周内改为每天摄入 3.3 份低脂或全脂乳制品。主要结局包括口服葡萄糖耐量试验期间的葡萄糖耐量（曲线下面积）、胰岛素敏感性、胰岛β细胞功能、全身炎症、肝脂肪含量以及体重和体成分。
在符合方案分析（n=67）中，我们未观察到干预对葡萄糖耐量的影响（P=0.340）。低脂和全脂乳制品饮食均降低了胰岛素敏感指数（Matsuda ISI）（均值±标准差分别为-0.47±1.07 和-0.25±0.91），与限制乳制品组（0.00±0.92）相比差异有统计学意义（P=0.012，总体）。体重也有差异变化（P=0.006，总体），与限制乳制品饮食相比，全脂乳制品组体重增加（+1.0kg；-0.2，1.8kg），而低脂乳制品组体重无明显变化（+0.3kg；-1.1，1.9kg）。调整肥胖变化后，干预对 Matsuda ISI 的影响仍然存在。未发现干预对肝脂肪含量或全身炎症有影响。意向治疗分析（n=72）的结果一致。
与我们的假设相反，两种乳制品饮食均未改善代谢综合征患者的葡萄糖耐量。两种乳制品饮食均通过与胰岛素敏感性关键决定因素变化无关的机制降低了胰岛素敏感性。本试验在 clinicaltrials.gov 上注册为 NCT02663544。
