PNAS：陈春英院士团队发现，微塑料可作为碳源进入体内碳循环，干扰代谢和肠道健康

Core Viewpoint - The article highlights the environmental and health risks associated with biodegradable plastics, particularly polylactic acid (PLA), which, despite being marketed as eco-friendly, can lead to significant health issues and metabolic disturbances in humans and animals [2][3][12]. Group 1: Environmental Impact of Biodegradable Plastics - The widespread use of plastics has led to the pervasive presence of microplastics (MP) and nanoplastics (NP) in the environment, with humans ingesting approximately 0.1 to 5 grams of microplastics weekly [2]. - PLA is the most produced and consumed biodegradable plastic globally, commonly used in food packaging and disposable utensils, but it has been found to generate more microplastics than traditional petroleum-based plastics [2][12]. Group 2: Health Risks Associated with PLA Microplastics - Recent research indicates that PLA microplastics can enter the carbon cycle within the body, disrupting metabolism and damaging the gut [3][4]. - The gut microbiome plays a crucial role in degrading PLA microplastics, with specific bacteria like Helicobacter muridarum and Barnesiella viscericola being responsible for this process, which can lead to the production of harmful byproducts such as uric acid and D-lactic acid [6][7]. - Long-term exposure to PLA microplastics has been shown to reduce appetite and cause weight loss in mice, with lasting metabolic disruptions even after cessation of exposure [7][12]. Group 3: Misconceptions About Biodegradable Plastics - The article emphasizes that "biodegradable" does not equate to "safe," as PLA requires high temperatures and humidity for effective degradation, conditions not met in the human body [10][12]. - The potential for gut bacteria to adapt to consuming plastics as a food source poses a risk to the balance of dietary fiber metabolism [10][12]. Group 4: Recommendations and Future Directions - The article calls for increased awareness of the "pseudo-environmental" trap of biodegradable plastics and suggests reducing the use of single-use plastic products, especially those in contact with high-temperature foods [12]. - It advocates for policy upgrades to reassess the safety standards of biodegradable plastics and promote the development of truly harmless materials [12][13].