Prebiotics and Phytochemicals: Food-Focused Approach to Gut Microbiota

In recent years, one of the most widely discussed topics in medicine is gut microbiota. Due to its indisputable importance for vigorous human life, it is even called the "hidden metabolic organ." According to the latest scientific data, the proper symbiosis between gut microbiota and the human organism is probably the main determinant of good health. So, how can you ensure this happens?

Key takeaways:
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    Gut microbiota are the microorganisms that live in the gastrointestinal track and benefit human organism.
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    Prebiotics are compounds in food that promote the growth of gut microbiota.
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    Phytochemicals are chemicals found in plant-based foods that promote the growth of gut microbiota.
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    The intake of food/supplements containing prebiotics and/or phytochemicals could help to control/regulate certain health conditions.

Gut microbiota and human health

The human digestive tract is home for trillions of live microorganisms which are essential for ensuring of the body system homeostasis or simply put, its well-being. The gut microbiota population varies throughout a person's life. However, about one third of all microbiota-hosting digestive track are common to all healthy humans. Meanwhile, the rest of the composition of microbiota is unique to each individual.

According to the latest scientific research, changes in healthy gut microbial composition (microbiota dysbiosis) can lead to the formation of unhealthy conditions such as obesity, cancer, autoimmune, metabolic, and neurodegenerative diseases. There are many factors that could influence the microbiota composition changes, some of them are listed in the table below. Among all these factors, diet is the one which forms and regulates gut microbiota composition during your whole lifetime.

Factors regulating the composition of the microbiota

Factors independent from human behavior

  • Genetics;
  • Gestational age (pre-term birth or full-term birth);
  • Birth method (vaginal delivery or C-section);
  • Aging.

Factors dependent on human behavior

  • Feeding methods used during infancy (breast feeding, artificial milk, solid food introduction);
  • Use of medications (antibiotics, immunosuppressants, anti-diabetic drugs, etc.);
  • Dietary habits (carbohydrates intake, food preparation methods, etc.);
  • Environment (rural residence, urban residence, etc.);
  • Lifestyle (active lifestyle, active work, sedentary work, etc.).

Since it is proven that the nutrition plays an important role in ensuring the microbiota quality, it can even be employed to control/regulate certain persons health conditions. In this context, various nutritional supplements (such as: prebiotics and phytochemicals) are extensively studied.

Gut microbiota and prebiotics

Prebiotics are non-digestible food elements (mostly nondigestible oligosaccharides) that are selectively used by host microorganisms and thereby benefit gut function. They occur naturally in various fruits, vegetables, and fermented products, e.g., leeks, onions, Jerusalem artichokes, chicory, wheat, agave, kefir, etc. However, the amounts of prebiotics in most foods are very low. Therefore, to attain the necessary level of prebiotics in food supplements, during their production process, they are purified from foods containing them or artificially synthesized in laboratories.

Prebiotics benefit gut functions through direct or indirect effects. The direct effect from prebiotics appears due to their structural similarity to host glycans (specific polysaccharides) which prevent the adhesion of infectious microorganisms to the intestinal walls. While the indirect effect occurs through the stimulation of gut microbiota growth and division. The higher amounts of microbiota produce higher amounts of metabolites, i.e., chemical compounds that play a critical role to ensure healthy organism conditions (e.g., maintaining a healthy gut pH, modulation of immune function, etc.).

There are many known prebiotics which are used as food supplements. Also, thanks to the hard work of researchers in this field, more and more new compounds are classified as prebiotics. The table below describes the most popular prebiotics and their beneficial outcomes.

Prebiotics and their outcomes

PrebioticBenefit to host
Human milk oligosaccharides (HMO)Prevention of pathogens binding to host gut walls; anti-inflammatory effect; protection from diarrhea, necrotizing enterocolitis, respiratory tract infections, and diabetes.
Fructooligosaccharides (FOS)Anti-inflammatory effect; anti-cancer effect; lower blood glucose level; protection from diarrhea; reduces atopic dermatitis.
InulinImmunomodulatory action; improvement of bowel function; anti-cancer effect; increase in bifidobacteria population; improvement of mineral absorption.
Galactooligosaccharides (GOS)Immunomodulatory action; inhibition of pathogen adhesion to the intestinal walls; reduces atopic dermatitis.
Mannan-oligosaccharides (MOS)Immunomodulatory action; inhibition of pathogen adhesion to the intestinal walls.
Xylooligosaccharides (XOS)Immunomodulatory action; anti-inflammatory effect; anti-cancer effect.

Gut microbiota and phytochemicals

Phytochemicals are chemical compounds naturally found in plants. Many of them play a key role in plant growth and development. For example, phytochemicals give plants their color, flavor, and aroma; protect plants from harmful agents (insects, microbes, etc.) and stressful events (UV irradiation, extreme temperatures, etc.); attract animals and insects which promote pollination and seed dispersal.

Scientific studies demonstrate that phytochemicals are important not only for plants but also can positively impact the human organism. Due to the complex chemical structure, the bioavailability and absorption of phytochemicals in the human body are very low. This leads to their extended retention times in the intestine and finally their positive effect on gut microbiota reproduction. Meanwhile, the microbiota enzymatically acts (“digests”) on the high molecular-weight phytochemicals remaining in the large intestine, resulting in metabolites, which finally benefit the organism by decreasing inflammation, reducing the formation of carcinogenic compounds, slowing cancer cells' growth rate, positively modulating the immune system, etc.

Phytochemicals that benefit the human organism can be found in all plant-based foods, e.g., fruits, vegetables, seeds, nuts, whole grains, legumes, dark chocolate, tea, etc. Currently, five main polyphenols groups can be distinguished: polyphenols, alkaloids, terpenoids (carotenoid terpenoids and non-carotenoid terpenoids), organosulfur compounds, and nitrogen-containing compounds. Although plants contain thousands of phytochemicals that are still undiscovered, thus their classification in the future could change.

How to improve your intake of prebiotics and phytochemicals

Asian and Mediterranean diets are abundant in prebiotics and phytochemicals rich fruits, vegetables, salads, spices, herbs, teas, nuts, seeds and legumes, while Western diets are deficient in them. Therefore, it is recommended to consume a lot more of prebiotics and phytochemical-rich foods with every meal of the day for those on a Western diet.

On the other hand, the market is full of food-supplements rich in prebiotics or phytochemicals, which, if produced properly, can really increase the prebiotics and phytochemicals intake across the day. However, most of them have not been evaluated in robust medical trials.

Finally, if you seek to improve your organism health by a diet the most important thing is balance. Because every food or supplement, even a useful one, can become harmful when the intake is excessive.

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