Metabolic

are they good for you

Diet can affect your health and quality of life by acting on the gut microbiota

Thoughtful proverbs have always pointed to the relationship between diet and health, but it is only more recently that we have begun to uncover the mechanisms by which it works. The diet or food that we ingest with our food also aids the growth and metabolism of our gut microbiota, which can affect our health.

Simply put, a diet is a description of the foods we eat. We hear of many trending diets with suggested health benefits including weight loss, improved immune and metabolic function, or improvement in gastrointestinal symptoms, such as the Mediterranean diet, ketogenic diets, low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diets , and the gluten-free diet. There are also recommendations for calorie restriction or intermittent fasting (only eating in a small window of time) to improve energy, metabolic function and weight loss.

Restrictive diets are not without side effects, however, as they can lead to nutritional complications if not monitored by a health professional. For example, the gluten-free diet is medically indicated for patients diagnosed with celiac disease, but requires an expert and medical evaluation to mitigate the long-term nutritional deficiencies in fiber, vitamin D, or iron that can contribute to complications (1). Likewise, it has recently been shown that calorie restriction can increase susceptibility to infection and multiply bacteria that metabolize the protective mucous layer in the colon (2).

The messages in the media can be confusing to patients and the public, so more research is needed to develop clear recommendations. Many exciting papers on this topic have been published this year.

In this roundup, we focus on a new approach rather than removing food components and adding fermented foods and prebiotic fiber to our diet, which can support the diversity of the gut microbiota.

Fermented foods to feed a healthy gut microbiota

When we hear fermented foods we might immediately think of foods like kombucha and probiotic yogurt, but the truth is that bread, cheese, meat, and even alcohol are fermented foods. It is estimated that there are over 5000 types of fermented foods worldwide (3)!

But what does fermentation mean and why is it an important part of the food industry? In the context of the production of food, fermentation has a general definition that includes any type of process that uses the desired microbial growth and enzymatic conversion of food components. In the past, the sometimes accidental use of fermentation has helped create safer, longer-lasting foods in regions of the world without clean water or electricity (4).

Today, selecting desirable microorganisms such as bacteria and yeasts to utilize the products derived from their metabolism (“starter cultures”) is an essential part in making unique yogurts, sourdough breads, and kombucha brews with suggested health benefits from the gut microbiota. However, many fermented foods do not contain live microorganisms and are not required to have any health benefits. Interestingly, the fermented foods that affect the immune system are further broken down by microbes into substances that are found in small amounts, such as polyphenols, which have health-promoting effects in the body (4).

Why do fermented foods get so much attention?

There is little clinical evidence in humans that certain fermented foods such as kombucha or kimchi can consistently alter the microbiome to treat gastrointestinal disorders, in part due to the variation in microorganism cultures in different locations (5). However, There is some evidence that fermented foods can be beneficial as part of a varied diet, for example due to their anti-inflammatory properties (6). Although these results are not specific to a disease or genetic status, they can indicate potential benefits in patients with chronic inflammatory diseases.

The results of a recently published small longitudinal study in healthy adults showed that six servings of a variety of fermented foods per day increased gut microbiota diversity and reduced inflammation (7), although the study was limited by the scope and lack of appropriate controls. Currently, there is simply not enough evidence to make clear recommendations on how to consume fermented foods to improve certain conditions, and caution should be exercised as overdosing on such fermented foods can also cause symptoms in some individuals.

So what diet is best for your gut microbiota?

The scientist’s favorite answer – “It depends!” The gut microbiota is a complex fingerprint of the individual, both in terms of composition and function, so there is no single form of nutrition that optimally supports bacterial growth and metabolism for everyone.

In order to make informed decisions about how to feed ourselves, we need to educate ourselves about our bacteria. The different communities of an individual can ferment the same types of fiber at different rates to produce different metabolite profiles that can affect the immune system (8). For example, we know that most celiac patients who follow a long-term gluten-free diet may need nutritional support, but supplementing with the wrong type of fiber can lead to gas or constipation.

Is it because of the bacteria or the type of fiber? It can be one or the other, or even both. In the future, when practice catches up with theory, we may be able to use an individual diet tailored to our specific gut bacteria. We need to learn more about how microbial profiles related to health can be influenced by diet or disease. A large study (Personalized Responses to Dietary Composition Trial (PREDICT-1)) used fecal metagenomic sequencing to examine the effects of long-term dietary patterns and found many strong microbial associations with certain foods in the UK that have been validated in the US (9) . However, more studies are needed on how certain food components such as fermented foods or fiber are used by the gut microbiota in order to be able to provide effective recommendations for patients.

Take home messages:

  • A varied, balanced diet is a sensible approach to supporting intestinal and microbiome health, as long-term restrictive diets can lead to nutrient deficiencies.
  • Fermented foods have historically increased the shelf life and safety of foods.
  • Fermented foods can increase the microbial diversity in the gut and reduce the host’s immune response, but in some individuals they can cause gastrointestinal symptoms.
  • Understanding the interactions between nutrition and the microbiome and how they work will help us achieve precise modulation of nutrition and the microbiome for optimal health.

References:

1. Cardo A, Churruca I, Lasa A, Navarro V, Vázquez-Polo M, Perez-Junkera G, et al. Nutritional imbalances in adult celiac patients after a gluten-free diet. Nutrient. 2021; 13 (8): 2877. doi: 10.3390 / nu13082877.

2. von Schwartzenberg RJ, Bisanz JE, Lyalina S, Spanogiannopoulos P, Ang QY, Cai J, et al. Calorie restriction disrupts the microbiota and colonization resistance. Nature. 2021; 595 (7866): 272-277. doi: 10.1038 / s41586-021-03663-4.

3. Tamang JP, Watanabe K, crabapple WH. Review: Diversity of Microorganisms in Globally Fermented Foods and Drinks. Microbiol. 2016; 7: 377. doi: 10.3389 / fmicb.2016.00377.

4. Marco ML, Sanders ME, Gänzle M, Arrieta MC, Cotter PD, De Vuyst L, et al. International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol. 2021; 18 (3): 196-208. doi: 10.1038 / s41575-020-00390-5.

5.Dimidi E, Cox SR, Rossi M, Whelan K. Fermented foods: definitions and properties, effects on gut microbiota, and effects on gastrointestinal health and disorders. Nutrient. 2019; 11 (8): 1806. doi: 10.3390 / nu11081806.

6. SaeidiFard N, Djafarian K, Shab-Bidar S. Fermented foods and inflammation: a systematic review and meta-analysis of randomized controlled trials. Clin Nutr ESPEN. 2020; 35: 30-39. doi: 10.1016 / j.clnesp.2019.10.010.

7.Wastyk HC, Fragiadakis GK, Perelman D, Dahan D, Merrill BD, Yu FB, et al. A diet geared towards the intestinal microbiota modulates the immune status of humans. Cell. 2021; 184 (16): 4137-4153.e14. doi: 10.1016 / j.cell.2021.06.019.

8. Chen T, Long W, Zhang C, Liu S, Zhao L, Hamaker BR. The fiber utilization capacity varies in Prevotella- and Bacteroides-dominated intestinal microbiota. Sci Rep. 2017; 7 (1): 2594. doi: 10.1038 / s41598-017-02995-4.

9. Asnicar F, Berry SE, Valdes AM, Nguyen LH, Piccinno G, Drew DA, et al. Microbiome Associations with Host Metabolism and Habitual Diet of 1,098 Deeply Phenotyped Individuals. Nat. Med. 2021; 27 (2): 321-332. doi: 10.1038 / s41591-020-01183-8.

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