低碳水化合物饮食和低脂肪饮食对2型糖尿病患者体质量及血糖的影响

碳水化合物与慢性病的关系密切，研究日益增多，然而对碳水化合物质量的描述尚未有明确的定义。目前常用的指标包括膳食纤维含量、全谷物摄入量、游离糖摄入量、血糖生成指数（Glycemic index，GI）这四个方面。高质量的碳水化合物食物一般具有高膳食纤维、全谷物食物高摄入量、低游离糖、低GI的特性，其中GI与人体血糖应答直接相关，是描述碳水化合物质量的重要指标。本文从消化吸收、加工方式、淀粉的组成和结构等三个方面总结了影响GI的因素，并对不同食物来源的GI进行了分析。消化吸收速度、不同加工方式都可影响GI，而淀粉的组成和结构对GI也有直接影响。直链淀粉和支链淀粉的结构组成不同，相比于直链淀粉，支链淀粉具有更多的淀粉酶结合位点，从而有更高的消化速率。因此直链淀粉含量高的食物，GI值相对低。根据淀粉中所含支链淀粉晶型可以将淀粉分为A型、B型、C型，3种类型的淀粉中，A型最容易消化，B型和C型不易消化，具有低GI特性。淀粉微观结构的研究将有助于深入了解GI的影响因素和为食物碳水化合物质量的评价补充一个新的角度。

Low-carbohydrate diets and cardiometabolic health: The importance of carbohydrate quality over quantity

Carbohydrates play a crucial role in the development of chronic diseases, and although research in this area is expanding, the precise definition of carbohydrate quality remains unclear. Currently, commonly utilized indicators encompass dietary fiber content, whole grain intake, free sugars intake and the glycemic index (GI). High-quality carbohydrate foods typically exhibit high dietary fiber content, consist of whole grain components, contain low levels of free sugars, and possess a low GI. The GI, in particular, directly influences the human blood sugar response and serves as a vital measure for describing carbohydrate quality. This article provides a comprehensive overview of the factors that influence the GI, focusing on three aspects: digestion and absorption, processing methods, and starch composition and structure. It further examines the GI values of various food sources. The rate of digestion and absorption, as well as diverse processing methods, can influence the GI. Additionally, the composition and structure of starch directly affect the GI. Amylose and amylopectin exhibit dissimilar structural compositions, with amylopectin containing more amylase binding sites than amylose, leading to a higher digestion rate. Consequently, foods with elevated amylose content tend to have relatively low GI values. Additionally, starch can be categorized into three types (A-type, B-type, and C-type) based on the crystal form of amylopectin present in the starch. Among these types, A-type starch is the most readily digestible, while B-type and C-type starch exhibit low GI characteristics due to their reduced digestibility. By studying the microstructure of starch, researchers can gain valuable insights into the influencing factors of the GI, thereby introducing a fresh perspective to the assessment of food carbohydrate quality.