Connie: Dear friends, thank you for tuning into our program again this Saturday evening. Previously in our program, we talked about various characteristics and applications of probiotics and relevant information on lactic acid bacteria. And today, we will be focusing on prebiotics. Thank you for joining us again, Dr. Hofstadter.
Dr. Hofstadter: Thanks for inviting me, Connie. Good evening, everyone. I’m very excited to be here.
Connie: There is a saying that all health problems start and resolve from the intestines. Does the gut microbiota have scientific research support for physical health or disease treatment?
Dr. Hofstadter: Certainly. Many studies have agreed on the supporting role of the gut microbiota in maintaining the overall health of subjects. Including the effects on mood, anxiety, and minimizing the symptoms of some common gastrointestinal diseases, as well as infections in life-threatening conditions. So yes, this ancient saying foresees the efforts of microorganisms to maintain a healthy gut.
Connie: We now know a lot about probiotics from our previous discussions. And we also have another term, which is prebiotics. What can you tell us about prebiotics and their health benefits?
Dr. Hofstadter: Prebiotics are oligosaccharides extracted from the plant and mammalian milk or industrially synthesized by enzymatic hydrolysis. They are used by probiotics in the intestines. Prebiotics has health benefits such as promoting intestinal flora, enhancing mineral absorption and host immunity, preventing cardiovascular diseases, cancer, diabetes, and lowering cholesterol levels.
Connie: So in other words, the most basic prebiotics is carbohydrates, but the definition does not exclude noncarbohydrate substances used as prebiotics. In theory, any substance that can reduce harmful bacteria and promote health can be called prebiotics. Which carbohydrates are prebiotics?
Dr. Hofstadter: The commonly used prebiotics include oligosaccharides, including fructooligosaccharides, galactooligosaccharides, xylooligosaccharides, Isomaltooligosaccharides, soybean oligosaccharides, inulin, and so on. In addition, some microalgae can also be used as prebiotics, such as spirulina, Arthrospira. And some polysaccharides, protein hydrolysates, vegetables, Chinese herbal medicine, and wild plants in natural plants can also be used as prebiotics.
Connie: Any common characteristics of prebiotics?
Dr. Hofstadter: Yeah, especially including various short-chain carbohydrates, prebiotics cannot be digested by enzymes in the upper digestive tract. It is believed that they have a beneficial effect on improving the health of the host by stimulating the metabolism of selected bacteria in the large intestine. Oligosaccharide prebiotics has the basic characteristics of soluble dietary fiber. For example, they can reduce fecal pH, Reduce toxic metabolites; Increase fecal volume and moisture, accelerate intestinal peristalsis and reduce constipation; they have the functions of cleaning intestines, defecating, detoxifying and detoxifying. In addition, oligosaccharide prebiotics also has good digestion resistance. They are not easy to be decomposed by enzymes in saliva, pancreatic juice, and intestinal juice. They can reach the large intestine and be metabolized by intestinal bacteria.
Connie: So you meant that prebiotics is not absorbed or hydrolyzed in the body, but are fermented by bacteria, which in turn changes the intestinal microflora and has a positive impact. Is this the advantage of prebiotics over probiotics?
Dr. Hofstadter: Absolutely. In order to maintain the microecological balance of intestinal flora, we can supplement probiotics or prebiotics. Probiotics have vitality, which is not easy to maintain, and generally have been destroyed when passing through the digestive tract. In addition, probiotics have some disadvantages, such as poor colonization ability in the GI tract and short residence time. Prebiotics don’t have these problems and so they are better intestinal micro ecological balance regulators.
Connie: What criteria does a substance need to be considered as a prebiotic?
Dr. Hofstadter: Let’s see. First, the substance will not be digested or absorbed by the host’s GI tract and can reach the large intestine completely. Second, it can only be used by one or several beneficial bacteria resident in the intestine to promote its growth, reproduction, or metabolic activity. Third, It can improve the composition of intestinal flora and promote host health. Finally, it can induce systemic immunity in the intestinal cavity and improve the host constitution.
Connie: You mentioned earlier that prebiotics can stimulate the growth and activity of probiotics in the GI tract. In addition, when the administered Prebs are not digested by the intestinal microflora, they enter the colon intact. What can be attributed to the indigestible properties of prebiotics?
Dr. Hofstadter: That is due to β-glycosidic bonds in the sugar unit because human digestive enzymes cleave α-glycosidic bonds specifically.
Connie: Is the mechanism of action of prebiotics on probiotics direct or indirect?
Dr. Hofstadter: It could be direct or indirect. In the direct mechanism, prebiotics directly inhibits pathogenic bacteria by forming antibacterial compounds, competing for nutrients, and adhering to the epithelial wall. It also regulates fat and carbohydrate metabolism by forming short-chain fatty acids, reducing the risk of cardiovascular disease and gastrointestinal infections. In the indirect mechanism, prebiotics tends to promote the absorption of essential minerals and nutrients, such as calcium and magnesium, to nourish the intestinal microbiota and promote its growth. Due to its species-specific MOA, prebiotics can enhance the overall metabolism and microbial composition of the intestinal tract.
Connie: What are the main flora that belongs to the intestinal flora stimulated by the action of prebiotics?
Dr. Hofstadter: In the intestinal flora stimulated by the action of prebiotics, there are various lactobacillus and bifidobacterium. Most of the prebiotics identified so far can promote the proliferation of bifidobacteria, and its mechanism is that prebiotics selectively stimulate the proliferation of bifidobacteria in the intestinal flora. This may be because bifidobacteria use this kind of substrate to grow more efficiently than other microorganisms, and can tolerate short-chain fatty acids and acidified microenvironment caused by fermentation. The analysis of the Bifidobacterium longum genome reveals a large number of protein sequences specialized in the catabolism of various carbohydrates, which undoubtedly help to improve the competitiveness in the intestinal environment.
Connie: Why are gut microbes stimulated by carbohydrates that are prebiotics?
Dr. Hofstadter: Because gut microbes have a natural tendency to use prebiotic sugars. Intestinal microbes concentrate on prebiotics to enhance functional activity. As we mentioned earlier, prebiotics is resistant to hydrolysis and absorption in the digestive system of mammals. Therefore, prebiotics passes through the small intestine to reach the lower intestine in undigested form, where they are eventually taken up by the intestinal flora for fermentation.
Connie: What substances are produced during the fermentation of prebiotics? What are the effects of these substances?
Dr. Hofstadter: Prebiotics fermentation releases short-chain fatty acids, namely butyric acid, acetic acid, lactic acid, and propionic acid. The formation of short-chain fatty acids is related to enhancing various physiological functions, including mineral absorption, intestinal function, regulating glucose and lipid metabolism, and reducing the risk of colon cancer. In addition, the consumption of prebiotics stimulates the growth of beneficial microorganisms and inhibits the growth of pathogenic bacteria.
Connie: Can you give us an overview of the health effects of prebiotics in the host, including improving intestinal health?
Dr. Hofstadter: Sure. You know that the MOA of prebiotics is largely theoretical, so researchers have assumed that their roles include improving the activity of microbial flora and the metabolic activity of microbial flora. Its benefits are to enhance intestinal colonization resistance, promote the absorption of mineral elements, improve immunity, nutrition, and the antitumor effect of short-chain fatty acids, defecate and reduce the metabolism of harmful microorganisms.
Connie: Wow, that’s amazing that prebiotics can be so beneficial to our health. And according to the experiments in the existing literature, what are the indicators used to evaluate the effect of prebiotics?
Dr. Hofstadter: Some indications are the proliferation of beneficial bacteria, the inhibition of harmful bacteria, and the non-proliferation of potentially pathogenic bacteria, as well as the acid and gas production after being metabolized by intestinal flora. Among them, the harmful bacteria in the human intestine are mainly referred to as Clostridium. In addition, some facultative bacteria will also be transformed into harmful bacteria that are not conducive to human health, such as Escherichia coli, Bacteroides, and so on. Successful prebiotics should not only be able to proliferate beneficial bacteria, but also inhibit the proliferation of harmful bacteria.
Connie: Now I’m very curious, how do we obtain prebiotics?
Dr. Hofstadter: Prebiotics can be obtained by extracting biologically active substances from plants and microorganisms. In addition, prebiotics can also be obtained through biochemical means, such as enzymatic hydrolysis of long-chain oligosaccharides.
Connie: We are at the end of today’s episode. Let me conclude today’s discussion. Because prebiotics can not be decomposed, absorbed, and utilized by the human body, some can be decomposed and utilized by the colonic flora after reaching the colon through the digestive tract, so as to promote the growth of colonic flora. Prebiotics are very important in improving intestinal microecology and promoting lipid, protein, and mineral metabolism. Therefore, they have become more widely used in food, feed, and other fields. That’s it for today. Thanks, Dr. Hofstadter, for another great discussion. And thanks everyone for listening. In the next episode, we will discuss the types of carbohydrates that belong to prebiotics. See you next time.
Dr. Hofstadter: Thank you for having me. I hope you enjoyed today’s topic and we will see you next time.