Group 1: Sources of Sweetness - Sweetness primarily comes from natural sugars, artificial sweeteners, and natural substitutes. Natural sugars like sucrose, glucose, and fructose are found in fruits and honey, providing energy to the body. Artificial sweeteners, such as aspartame and saccharin, are chemically synthesized and offer high sweetness with minimal calories, catering to those managing sugar intake. Natural substitutes like erythritol and steviol glycosides are plant-derived, retaining sweetness with lower calories and minimal impact on blood sugar levels [1][2]. Group 2: Human Preference for Sweetness - The preference for sweetness is ingrained in human genetics and habits, as sweet foods typically indicate high energy content. Sugars are essential carbohydrates, providing 50%-70% of the energy required for life activities. Different types of sugars, including glucose and fructose, can be directly utilized by the body, while others need to be converted into monosaccharides for metabolism [2][3]. Group 3: Distinction Between "Sweet" and "Guan" - In Chinese culture, "甘" (sweet) and "甜" (sweet) have nuanced differences. "甘" is associated with a mild sweetness and medicinal properties, while "甜" refers solely to taste perception. For instance, honey is sweet and classified as "甘," but artificial sweeteners, though sweet, lack the health benefits associated with "甘" [3][4]. Group 4: Health Implications of Sweetness - Moderate consumption of sweet foods can benefit energy and digestion, but excessive intake may lead to health issues like obesity and dental problems. The recommended daily sugar intake is no more than 50 grams, ideally under 25 grams, especially for children and those with specific health conditions [6][7]. Group 5: Sugar Control Strategies - Effective sugar control involves distinguishing between natural and added sugars. Natural sugars found in fruits and dairy are generally safe, while added sugars in processed foods should be limited. Strategies include choosing whole foods, reducing sweet snacks, and being mindful of sugar content in pre-packaged items [8][9][10].

Core Viewpoint - The article discusses the hidden dangers of the American food industry, highlighting that despite the perception of safety and cleanliness, there are significant health risks associated with food additives and regulatory practices in the U.S. [6][10][36] Group 1: Food Safety Perception - Many newcomers to the U.S. initially believe that American food is clean and safe due to extensive regulations and detailed labeling [5][6] - However, long-term residents are aware that the reality is more complex, with many food products containing harmful additives [7][9] Group 2: Health Issues Linked to Food - The U.S. has the highest obesity rate globally, with rising cases of diabetes and other chronic diseases, attributed to systemic issues within the food industry [9][10] - The food industry focuses on stimulating consumption rather than nutritional value, using additives that may disrupt metabolic processes [10][11] Group 3: Regulatory Concerns - The article highlights the flaws in the U.S. food regulatory system, particularly the GRAS (Generally Recognized As Safe) policy, which allows companies to self-assess the safety of food additives [21][24] - There are over 10,000 chemical substances added to food, with about 1,000 of them lacking clear safety assessments from the FDA [18][19] Group 4: Calls for Change - Controversial figure Robert F. Kennedy Jr. has called for the elimination of certain harmful food additives, which are already banned in the EU, highlighting the need for reform in U.S. food safety regulations [14][32] - Experts suggest that the FDA's evaluation methods are outdated and fail to consider the cumulative effects of multiple chemical exposures [24][25] Group 5: Consumer Awareness - The article emphasizes the importance of consumer vigilance regarding food ingredients, as many people are unaware of what they are actually consuming [42][47] - It suggests that the perception of transparency in food labeling is misleading, as many risks remain hidden from consumers [44]

来源：中国科学报 糖在激活味蕾的同时，给公众健康带来了负面影响。而糖究竟是如何"诱惑"人类味觉的一直是个谜。 一项5月7日发表于《细胞》的研究朝着解开上述谜团迈出了决定性一步。科学家首次绘制出人类甜味受 体的分子结构图，并展示了两种使用最广泛的人造甜味剂是如何与甜味受体结合并激活它的。 然而，经过20多年的研究，虽然科学家已经破译了其他味觉受体的结构，如苦味受体，但甜味受体的精 确结构仍然难以捉摸。 该研究详细分析了舌头是如何感知甜味的，并可能为生产更健康的碳酸饮料、口香糖和其他糖果铺平道 路。 现在，Zuker的团队终于确定了甜味受体的结构。研究人员将脆弱的蛋白质复合物稳定在活性构象中， 这是高分辨率成像的关键先决条件。随后，他们使用冷冻电子显微镜，捕获了与三氯蔗糖和阿斯巴甜这 两种人工甜味剂结合的受体的原子级快照。 图像显示，TAS1R2亚基有一个可被三氯蔗糖或阿斯巴甜占据的区域。然而，它们的结合方式略有不 同，暗示了受体存在一种灵活的结合机制，使其能够识别各种甜味化合物。TAS1R3亚基则不参与结 合，但它在帮助组装和稳定受体复合物方面发挥了重要作用。 "这种单一受体导致了人类对糖永不满足的渴求。现在了 ...

撰文丨王聪 编辑丨王多鱼 排版丨水成文 " 甜味 "是人类最具代表性且跨越文化的典型感官体验之一，它能激发人类和动物的食欲反应，促使摄入高 能量的食物来源，并促进包含关键宏量营养素的饮食。在人类身上，它还会唤起愉悦、满足和舒适的感 觉。 早在 2001 年， Charles S. Zuker 等人就发现了哺乳动物的甜味受体 ，表明了 它是由两种蛋白质 TAS1R2 和 TAS1R3 组成的 异源二聚体，属于 C 族 G 蛋白偶联受体 （ Class C GPCR ） 。 值得注意 的是，这个单一的甜味受体能够识别各种甜味化合物，包括天然糖类、人工甜味剂、D-氨基酸以及一类甜 度极高的蛋白质；实际上，这些化学物质之所以尝起来"甜"，是因为它们激活了这种共同的甜味受体。 近年来，几种哺乳动物感觉受体的结构已陆续被解析 （包括温度、机械、嗅觉、苦味、痒觉以及痕量胺受 体） ，尽管人类甜味受体在人类味觉中至关重要，但其结构却一直未被解析。 2025 年 5 月 7 日，哥伦比亚大学 Charles S. Zuker 实验室 （ 博士后 张举恩 和博士生 陆政元 为论文共 同第一作者） 在国际顶尖学术期刊 Cell 上 ...