Regulation of intestinal flora
Frequency of use of functional foods

Functional foods for regulating intestinal flora are mainly based on probiotics, traditional Chinese medicines that can be used in health food, traditional Chinese medicines of the medicinal food category, and ordinary foods. As of July 1, 2016, the data query results of the State Food and Drug Administration (CFDA) showed that a total of 106 domestic functional foods for regulating intestinal flora were approved, 86 types of raw materials were used, and the cumulative frequency was 387 times.

Among them, there are 15 types of probiotics with a frequency of 114 times, and the top 5 in order of frequency are Lactobacillus acidophilus, Bifidobacterium longum, Lactobacillus casei, Streptococcus thermophilus and Bifidobacterium amphotericus;

The next highest frequency of use was for oligosaccharides, which amounted to 47 times, followed by oligofructose 28 times and oligosaccharides 19 times;

There are 18 kinds of medicinal and food materials, used 34 times, according to the frequency of use of the top 5 in order of Chen Pi, Poria, cassia seeds, sand nuts, hawthorn;

Health food raw materials of 14 kinds, the frequency of use is 17 times, according to the frequency of use of the first 5 in order of Codonopsis, Atractylodes macrocephala, Senna, Paeonia lactiflora, Radix et Rhizoma Dioscoreae;

Common food ingredients 14 kinds, the frequency of use is 74 times, according to the frequency of use of the top 5 for lemon, starch, corn, apple, chicory inulin;

25 kinds of food additives, the frequency of use is 148 times, according to the frequency of use of the top 5 oligofructose, dextrin, oligosaccharides, citric acid, isomaltooligosaccharides.

Regulation of intestinal flora
Classification and efficacy of functional foods

Functional foods approved for regulating intestinal flora are broadly categorized into 3 types. The first type uses probiotics as raw materials and directly supplements the body with probiotics to regulate intestinal flora. The second type is based on traditional Chinese medicine with other nutritional enhancers or ordinary food as raw materials, combining traditional Chinese medicine formulas, modern Chinese medicine theories and modern nutritional medicine based on the combination, adding different types of raw materials to regulate intestinal flora. The third type is to promote gastrointestinal motility and digestion through oligosaccharides and dietary fiber to regulate intestinal flora.

2.1 Oligosaccharides
Oligosaccharides are utilized by probiotics and promote the proliferation of beneficial intestinal bacteria, enhancing the competitive advantage of probiotics. When oligosaccharides enter the colon they can stimulate the growth of one or a few probiotic bacteria in the colon, favoring the growth of the host. The non-digestible substance oligosaccharides have the function of prebiotics, which can promote the growth of bifidobacteria, inhibit the propagation of conditionally pathogenic and harmful bacteria in the intestine, reduce the number of intestinal harmful bacteria, so as to regulate the micro-ecosystem of intestinal flora.

Studies have shown that isomaltooligosaccharides can increase the number of bifidobacteria strains, thus promoting intestinal peristalsis, preventing constipation, and clearing the intestinal tract, as well as inhibiting the reproduction of harmful and toxic bacterial strains. Gu Qing et al. found that isomaltooligosaccharide can promote the proliferation of Bifidobacterium and Lactobacillus and inhibit the growth of Clostridium perfringens by feeding 40 mice with low, medium and high dose of isomaltooligosaccharide and blank group of water as control respectively.

2.2 Active polysaccharides
Active polysaccharides have an important role in improving the intestinal mucosa and the immune process, protecting the structural integrity of the intestinal barrier as well as stimulating intestinal endocrine secretion, which can regulate the intestinal flora and maintain the health of the body.

Xu Yongjie et al. studied different extraction processes of burdock polysaccharides and found that the addition of burdock polysaccharides resulted in the proliferation of Lactobacillus and Bifidobacterium, and the higher the content of burdock polysaccharides, the higher the increase in the number of Lactobacillus and Bifidobacterium, and there was no significant change in the number of Enterobacteriaceae in the intestinal tract.

Chen Qinghua et al. fed diets with different contents of burdock polysaccharides to weaned piglets (all weighing about 8.898 kg) born in 28 d. It was found that the number of Escherichia coli and Bifidobacterium and Lactobacillus in the intestinal tracts of the piglets with the addition of burdock polysaccharides increased significantly.

2.3 Probiotics
Probiotics include two major groups of bifidobacteria (Bifidobacterium infantis, Bifidobacterium shortum, and Bifidobacterium adolescentis) and Lactobacillus (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus rohita).

Probiotics in the intestinal tract are able to bind to the intestinal mucosa, thus forming a biological barrier in the intestinal tract, and inhibit the proliferation and invasion of conditionally and exogenously pathogenic bacteria by utilizing their occupancy effect, competing for nutrients, and secreting a variety of metabolites and bacteriocins. Xie Caihong et al. found that Lactobacillus acidophilus helped to restore Lactobacillus, Bifidobacterium, and Enterococcus in the intestinal tracts of ceftriaxone-treated mice to the numbers prior to cephalosporin treatment.

Zhao Shengjuan et al. studied the bacterial flora of the rat intestine and found that the large proliferation of Bacillus natto in the intestines consumed a large amount of oxygen in the intestines, and the oxygen concentration in the intestines was significantly reduced, and the growth environment of anaerobic Bifidobacterium bifidum was well improved, while curbing the growth of aerobic Enterobacteriaceae and Enterococcus).

2.4 Dietary fiber
Dietary fiber is fermented in the large intestine to obtain usable plant-based components, carbohydrates and their analogs. At the 26th CCNFDU meeting dietary fiber was defined as carbohydrate polymers that are not digestible or absorbable in the small intestine and have a degree of polymerization of not less than 3 (or 10).

Dietary fiber includes water-insoluble dietary fiber and water-soluble dietary fiber, insoluble dietary fiber promotes intestinal peristalsis, while water-soluble dietary fiber affects the metabolic function of available carbohydrates and lipid metabolism, and the proportion of the composition of insoluble and water-soluble dietary fiber in the dietary fiber is critical to the physiological function of dietary fiber.