The closely related terms “fiber”, “microbiota accessible carbohydrates” (or MACs) and “prebiotics” may seem familiar. But what exactly are they and how do they contribute to good health and eradication of intestinal microbiota?

Fiber can be used by intestinal microbes, but this is not a requirement

We have known for some time that a diet high in fiber reduces the risk of developing chronic diseases and lowers mortality. However, scientists have begun to explain why fiber is important for human health in order to maintain the intestinal microbiota and immune system, which are primarily located in the small intestine, as explained by the scientific journalist Carl Zimmer. The New York Times.

Fiber is a very broad term and its meanings vary according to the country, but one statement Dietary fiber Includes “Carbohydrates that are produced by the individual microbiota and play an important role.. ”Similar to food fiber, polysaccharides, like microbiota, do not remove plant molecules, and human milk is an oligosaccharides that can alter microbiome, such as intestines.

Typically, fiber is classified according to its physical chemical properties, one of which is dissolution. For example, insoluble fibers such as cellulose, wheat bran, and lingin (found in grains and vegetables) can be used to treat constipation and ingestion of excess gastrointestinal gas. Meanwhile, soluble fibers such as pectins and psyllium (such as carrots, apples and oats) regulate bowel movements and suggest constipation to people who switch to diarrhea.

However, solubility alone does not predict the functional properties of fiber microbes in the stomach. And the fact is that foods are often a complex mixture of soluble and insoluble fibers, and cooking also affects the presence of dietary fiber in the stomach microbes.

Microbiota Accessible Carbohydrates: New term, included in fiber definition, for carbohydrates that should be contaminated with microbiota

Scientists have coined the idea that each type of fiber harms microbes in the gut differently. Microbiota Accessible Carbohydrates (MACs) represent a type of fiber, “carbohydrates that can be metabolized by intestinal microbes”.

MACs include dietary carbohydrates-From plant or animal tissues (eg animal baskets) or food-carrying microbes-Resistant to digestion and absorption by the host. But they may also be left behind by the host (e.g., mucus) or microbes.

One challenge to define MAC is the lack of dietary databases that measure the amount of food macros in a food source. For other types of carbohydrates, such as unstable starch, intestinal microbes can be multiplied, the databases record their content in foods that are commonly eaten. Databases, including those food sources, are needed to design dietary interventions aimed at microbes and to investigate related health outcomes. This is a complex issue, since most of the 26,000 different types of food in the diet have not yet been identified or measured.

In addition, intestinal microbes’ use of MAC in food sources depends on the composition of the individual’s intestinal microorganisms. The individuality of carbohydrates, such as MACs, indicates the presence of certain genes in the intestinal microbiome used in sushi in Japanese individuals. These genes are rarely found in individuals in North America and Europe, as they have been transmitted from sea bacteria to intestinal bacteria. Simply put, due to the lack of microbes to fertilize, one layer is not MAC for one person but for another.

Although at first glance the MAs look the same as prebiotics, The criteria described in the definition of prebiotics are that all MACs have scientifically supported health effects..

Choice of use by resident microbes and proven health benefits – Key characteristics that distinguish prebiotics from dietary fiber and mac

The latest definition of prebiotics In 2017, it was updated by microbiology, nutritionists and medical researchers at the International Scientific Association for Probiotics and Pesticides. It is described as “a layer of microorganisms that have been selected by health-promoting hosts.”

Although fiber may exhibit certain intestinal microbiome properties and express adequate digestive values, prebiotics should be selected and used by resident microbes and do not have adequate drinking or daily value levels.. Based on the 2000 kcal / day diet, 28 g / day is the daily value for dietary fiber, but the good news is that it is sufficient to increase the benefit by up to 5 g / day of small fiber. Bifidobacteria spp.

Insulin-type fructose (ie, insulin, oligosaccharides and fructose-oligosaccharides) and b-galactose-oligosaccharides have been extensively studied in prebiotics (carbohydrates).

Growing prebiotics are also selected by research in human milk oligosaccharides, polyunsaturated fatty acids and polyphenols, if selected by host microbiota and promote health.

Interestingly, insoluble fibers from wine production, such as protective starch and wine residues, are being explored as novel pre-biotics. This means that when the intestine is exposed to microbiome, the definition of fiber as soluble (non-digestible or non-digestible) is more significant, as fiber is soluble (ie, absorbed by water) and insoluble (ie, large).

Prebiotics It was primarily investigated In gastrointestinal disorders– For patients with primarily irritable bowel syndrome, their role in low-grade, intestinal obstruction is controversial:And as an immunization module method. For example, some prebiotics can help improve the effectiveness of the seasonal flu vaccine for older people. Adolescent data also suggest prophylaxis as a new strategy to improve age-related neurological disorders and brain function.

In general, food fiber, mac, and prebiotics are scientifically based tools to ensure that intestinal microbiome is in good condition. First, it includes fiber MAC and antibiotics. Second, while both MAC and prebiotics are used by intestinal microbes, not all MACs are considered prebiotics; It is a good idea to eat a lot of fiber as you try to improve each intestinal microbiome by setting aside the definitions, making it clear to scientists that it is important, and especially in the case of intestinal disorders.


Gill SK, Rossi M, Bajka B, et al. Dietary fiber in gastrointestinal health and disease. Nati Rev Gastrointestinal Hepatol. 2021 18 (2) 101-116. doi: 10.1038 / s41575-020-00375-4.

Sonnenburg ED, Sonnenburg JL. Microblastic self-starvation: Malnutrition-induced malnutrition-induced carbohydrates. Cell Metab. 2014 20 (5) 779-786. Link: 10.1016 / j.cmet.2014.07.003.

Patterson MA, Maya M, Stewart M. Stroke Content in Nutritious Foods in the United States – Narrative Review. J. Acad Nut Diet. 2020; 120 (2) 230-244. doi: 10.1016 / j.jand.2019.10.019.

Barabasi Al, Menicheti G, Loscalso J. Our disproportionate chemical complex. Natural food. 2020 1: 33-37. doi: 10.1038 / s43016-019-0005-1.

Hehemann JH, Correc G, Barbeyron T, et al. Carbohydrate: Transfer of active enzymes from sea bacteria to Japanese intestinal microbiota. Nature. 2010; 464 (7290) 908-912. doi: 10.1038 / nature08937.

Gibson GR, Hutkins R, Sanders ME, and others. Expert Consensus Document – International Scientific Association Probiotics and Prebiotics (ISAPA) Declaration on the definition and scope of microbiology. Nati Rev Gastrointestinal Hepatol. 2017; 14 (8) 491-502. Link: 10.1038 / nrgastro.2017.75.

Oliver L, Ramio-j Jol S, Amodo J, and others. A new pre-biobiotic vine develops booster-producing bacteria in fecal samples in quantity and metabolic activity. Facial microbiology. 2021 12 639948. doi: 10.3389 / fmicb.2021.639948.

Therefore, D, Whelan K, Rossi M, et al. Dietary fiber interventions in intestinal microbiota composition in healthy adults: systematic review and meta-analysis. MJ Clint Not. 2018; 107 (6) 965-983. doi: 10.1093 / ajcn / nqy041.

Wilson B., Willan K. Prebiotic Inulin-like Fractions and Galacto-Oligosaccharides: Definition, Differentiation, Function, and Gastrointestinal Disorders. J. Gastroenterol Hepatol. 2017; 32 Supply 1: 64-68. doi: 10.1111 / jgh.13700.

Lomax AR, Cheung LVY, Noakes PS, et al. In healthy middle-aged people, the insulin-like b2-1 fructose for seasonal influenza vaccine has a limited effect on the human immune system. Face Immunol. 2015; 6: 490. Link: 10.3389 / fimmu.2015.00490

Long-Smith C, Oriordan KJ, Clark G., and others. Microbiota-intestinal-brain stem-new treatment opportunities. Annu Rev Pharmacol Toxicol. 2020 60 477-502. doi: 10.1146 / annurev-pharmtox-010919-023628.