Abstract: The intestine is an important organ for metabolism in the human body. It is home to a large number of bacteria that play a vital role in the metabolic process. Flaxseed is rich in essential fatty acids, dietary fiber, lignans and other nutrients, and it has the function of preventing cardiovascular and cerebrovascular diseases, improving intestinal function, and regulating estrogen levels and so on. In order to explore the effect of ingestion of flaxseed on the human intestinal flora, healthy adult volunteers were recruited for receiving dietary intervention with flaxseed (0.6 g/(kg·d)) for 21 d. We collected fecal samples at the before and after the experimental period for high-throughput 16S rRNA gene sequencing and high-throughput gas chromatography analysis. The data showed that the intestinal microbial diversity (Shannon index) was increased after the intake of flaxseed, while the proportion of the dominant bacteria of Firmicutes in obese populations was down-regulated, and the content of short-chain fatty acids in all fecal samples was increased. This experiment proved that the intake of flaxseed could change the intestinal microflora structure of healthy adults, increase the intestinal microbial diversity, and promote the production of short-chain fatty acids (SCFA) in intestine, maintaining the intestinal microenvironment and preventing intestinal diseases. In additional, some changes in the structure of the intestinal microflora may be beneficial to prevent the risk of obesity.

Key words: flaxseed, intestinal microbes, short-chain fatty acids, microbial diversity