The human gut microbiome reaches 3.8 × 10e13 microbes in a standard adult male, which outnumbers the human host cells (3.0 × 10e13) [1]. Each individual hosts at least 160 species out of the total 1150 species that colonize the human GI tract [2].
Compared with human metabolism, bacterial metabolism is much more powerful considering the fact that the gut microbial genes (3.3 × 106) far outnumber human protein-coded genes by 150-fold [2].
肠道微生物的多样性与人体健康密切相关。肥胖、糖尿病、肠道疾病的人，肠道微生物多样性会比较低。
健康的微生物菌群：
-分泌抗菌物质、形成厚厚的屏障、保护肠粘膜、防止肠漏
一些特定的肠道微生物能够强烈诱导结肠调节性T细胞（Tregs）。
为什么要吃膳食纤维：
-维持菌群多样性
-保护肠粘膜
-在没有膳食纤维的情况下，有的细菌就开始消化肠道黏膜上的物质。
The fermentation of indigestible fibers causes the production of short chain fatty acids (SCFA) 短链脂肪酸that can be used by the body as a nutrient source but also play an important role in muscle function and possibly the prevention of chronic diseases, including certain cancers and bowel disorders. Clinical studies have shown that SCFA may be useful in the treatment of ulcerative colitis, Crohn’s disease, and antibiotic-associated diarrhea. [2] “溃疡性结肠炎、克罗恩病和抗生素相关性腹泻。” [2]
