英美澳荟萃分析发现：不饱和脂肪酸可改善糖尿病

　　2016年7月19日，美国《公共科学图书馆·医学》在线发表剑桥大学临床医学院代谢科学研究所、塔夫茨大学弗里德曼营养科学政策学院、悉尼大学医学院乔治全球健康研究所、德克萨斯大学休斯顿健康科学中心、迈阿密大学米勒医学院杰克逊纪念医院、哈佛大学陈曾熙公共卫生学院的研究报告，为膳食脂肪和碳水化合物对葡萄糖和胰岛素水平等其他几个2型糖尿病相关因素的调节提供了定量证据。

　　该研究对所有可获得的证据进行系统回顾，筛选出2015年11月26日前发表的6124篇摘要、102项随机对照试验，共涉及239个饮食研究组、4220位年龄≥18岁的成人，给予的饮食在脂肪和碳水化合物数量上有所不同。

　　经过荟萃分析，量化不同类型的膳食脂肪（饱和、单不饱和、多不饱和）和碳水化合物对葡萄糖和胰岛素控制关键生物指标（这些指标与2型糖尿病发展有关）的影响，评价了这些饮食差异如何影响代谢健康，包括血糖、血胰岛素水平、胰岛素抵抗和敏感性以及机体随血糖水平产生胰岛素的能力。

　　结果表明，以富含不饱和脂肪酸的饮食，代替膳食中的碳水化合物或饱和脂肪酸对血糖控制的关键指标产生了有益的影响。多食用不饱和脂肪酸（尤其是多不饱和脂肪酸）代替膳食中的碳水化合物或饱和脂肪酸，可以降低血糖水平，改善胰岛素抵抗和分泌。例如，以单或多不饱和脂肪酸代替碳水化合物获取能量，每用单、多不饱和脂肪酸获取5%的能量，长期血糖控制的指标HbA1c分别降低0.09%、0.11%。

PLoS Med. 2016 Jul 19;13(7):e1002087.

Effects of Saturated Fat, Polyunsaturated Fat, Monounsaturated Fat, and Carbohydrate on Glucose-Insulin Homeostasis: A Systematic Review and Meta-analysis of Randomised Controlled Feeding Trials.

Imamura F, Micha R, Wu JH, de Oliveira Otto MC, Otite FO, Abioye AI, Mozaffarian D.

Medical Research Council Epidemiology Unit, Institute of Metabolic Science, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, United Kingdom; Tufts Friedman School of Nutrition Science & Policy, Boston, Massachusetts, United States of America; George Institute for Global Health, The University of Sydney, Sydney Medical School, Camperdown, Australia; Human Genetics & Environmental Sciences, The University of Texas Health Science Center at Houston, Houston, Texas, United States of America; University of Miami Miller School of Medicine/Jackson Memorial Hospital, Miami, Florida, United States of America; Harvard T. H. Chan School of Public Health, Boston, Massachusetts, United States of America.

BACKGROUND: Effects of major dietary macronutrients on glucose-insulin homeostasis remain controversial and may vary by the clinical measures examined. We aimed to assess how saturated fat (SFA), monounsaturated fat (MUFA), polyunsaturated fat (PUFA), and carbohydrate affect key metrics of glucose-insulin homeostasis.

METHODS AND FINDINGS: We systematically searched multiple databases (PubMed, EMBASE, OVID, BIOSIS, Web-of-Knowledge, CAB, CINAHL, Cochrane Library, SIGLE, Faculty1000) for randomised controlled feeding trials published by 26 Nov 2015 that tested effects of macronutrient intake on blood glucose, insulin, HbA1c, insulin sensitivity, and insulin secretion in adults aged ≥18 years. We excluded trials with non-isocaloric comparisons and trials providing dietary advice or supplements rather than meals. Studies were reviewed and data extracted independently in duplicate. Among 6,124 abstracts, 102 trials, including 239 diet arms and 4,220 adults, met eligibility requirements. Using multiple-treatment meta-regression, we estimated dose-response effects of isocaloric replacements between SFA, MUFA, PUFA, and carbohydrate, adjusted for protein, trans fat, and dietary fibre. Replacing 5% energy from carbohydrate with SFA had no significant effect on fasting glucose (+0.02 mmol/L, 95% CI = -0.01, +0.04; n trials = 99), but lowered fasting insulin (-1.1 pmol/L; -1.7, -0.5; n = 90). Replacing carbohydrate with MUFA lowered HbA1c (-0.09%; -0.12, -0.05; n = 23), 2 h post-challenge insulin (-20.3 pmol/L; -32.2, -8.4; n = 11), and homeostasis model assessment for insulin resistance (HOMA-IR) (-2.4%; -4.6, -0.3; n = 30). Replacing carbohydrate with PUFA significantly lowered HbA1c (-0.11%; -0.17, -0.05) and fasting insulin (-1.6 pmol/L; -2.8, -0.4). Replacing SFA with PUFA significantly lowered glucose, HbA1c, C-peptide, and HOMA. Based on gold-standard acute insulin response in ten trials, PUFA significantly improved insulin secretion capacity (+0.5 pmol/L/min; 0.2, 0.8) whether replacing carbohydrate, SFA, or even MUFA. No significant effects of any macronutrient replacements were observed for 2 h post-challenge glucose or insulin sensitivity (minimal-model index). Limitations included a small number of trials for some outcomes and potential issues of blinding, compliance, generalisability, heterogeneity due to unmeasured factors, and publication bias.

CONCLUSIONS: This meta-analysis of randomised controlled feeding trials provides evidence that dietary macronutrients have diverse effects on glucose-insulin homeostasis. In comparison to carbohydrate, SFA, or MUFA, most consistent favourable effects were seen with PUFA, which was linked to improved glycaemia, insulin resistance, and insulin secretion capacity.

PMID: 27434027

PMCID: PMC4951141

DOI: 10.1371/journal.pmed.1002087