Department of Nutrition and Movement Sciences, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
Department of Internal Medicine, Division of Endocrinology and Metabolism, Maastricht University Medical Center, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands.
Nutrients. 2023 Feb 1;15(3):735. doi: 10.3390/nu15030735.
Current guidelines aim to limit the dietary glycemic index (GI) and intake of saturated fatty acids (SFA). Several studies have shown favorable effects of low-GI or low-SFA diets on intrahepatic lipid content (IHL), but these studies were performed under overfeeding conditions or extreme differences in GI or SFA to maximize the contrast between diets. By combining changes in GI and SFA, we can mimic how people can improve their diet in a realistic setting.
We investigated the effect on liver fat content and substrate metabolism of both reducing GI and replacing SFA with polyunsaturated fat in practically realistic amounts under isocaloric conditions.
In a randomized crossover study, thirteen overweight participants consumed two diets, one high in GI and SFA (high GI/SFA) and one low in GI and SFA (low GI/SFA) with identical macronutrient composition, for two weeks each. Diets were equal in caloric content, consisted of habitual food items, and had a macronutrient composition that can be easily achieved in daily life. At the end of each intervention, IHL content/composition and liver glycogen were measured by magnetic resonance spectroscopy. Additionally, fasted and postprandial hepatic de novo lipogenesis and glycemic and metabolic responses were investigated.
IHL was significantly lower (-28%) after the two-week low-GI/SFA diet (2.4 ± 0.5% 95% CI [1.4, 3.4]) than after the two-week high-GI/SFA diet (3.3 ± 0.6% 95% CI [1.9, 4.7], < 0.05). Although hepatic glycogen content, hepatic de novo lipogenesis, hepatic lipid composition, and substrate oxidation during the night were similar between the two diets, the glycemic response to the low-GI/SFA diet was reduced ( < 0.05).
Changes in macronutrient quality can already have drastic effects on liver fat content and postprandial glycemia after two weeks and even when energy content and the percentage of total fat and carbohydrate remains unchanged.
目前的指南旨在限制饮食血糖指数（GI）和饱和脂肪酸（SFA）的摄入量。多项研究表明，低 GI 或低 SFA 饮食可降低肝内脂质含量（IHL），但这些研究是在过量喂养或 GI 或 SFA 差异极大的情况下进行的，以便最大限度地对比不同饮食。通过结合 GI 和 SFA 的变化，我们可以模拟人们在现实环境中改善饮食的方式。
在等热量条件下，我们研究了实际情况下通过降低 GI 和用多不饱和脂肪替代 SFA 对肝脂肪含量和底物代谢的影响，实际摄入量接近现实情况。
在一项随机交叉研究中，13 名超重参与者分别食用两种饮食，每种饮食 GI 和 SFA 含量均较高（高 GI/SFA）和 GI 和 SFA 含量均较低（低 GI/SFA），每种饮食的宏量营养素组成相同，每种饮食持续两周。两种饮食的热量相同，由日常食物组成，宏量营养素组成在日常生活中很容易实现。在每轮干预结束时，通过磁共振波谱法测量肝内脂质含量/组成和肝糖原。此外，还研究了空腹和餐后肝内从头脂肪生成以及血糖和代谢反应。
与高 GI/SFA 饮食（3.3 ± 0.6% 95% CI [1.9, 4.7]）相比，低 GI/SFA 饮食（2.4 ± 0.5% 95% CI [1.4, 3.4]）后两周肝内脂质含量降低了 28%（P < 0.05）。尽管两种饮食之间的肝糖原含量、肝内从头脂肪生成、肝内脂质组成和夜间底物氧化相似，但低 GI/SFA 饮食的血糖反应降低（P < 0.05）。
即使能量含量和总脂肪及碳水化合物的百分比保持不变，仅改变宏量营养素的质量，两周后就可对肝脂肪含量和餐后血糖产生显著影响。
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