Sourdough bread is nutritionally a necessary food for our organism – effects of several diets on the microbiota

 In previous articles we have discussed and explained the subject of the microbiota and its function in our organism. You can read more about it here. Today we want to go deeper into this topic with a summary of a new scientific publication that proves that cultured sourdough bread is a healthy, necessary and beneficial food for the body. We want to contribute with this publication to deny once and for all that sourdough bread is a fattening food or that it should be replaced by other carbohydrates. If you want to know why? We invite you to continue reading.

The human intestinal microbiota is influenced by several factors; diet and modern lifestyle, among others, have contributed to generate a change in the microbial colonization patterns by altering the microbiota composition. Diet is considered one of the main drivers in the formation of intestinal microbiota throughout life. Because bacteria specialise in the fermentation of different substrates, diets can provide a range of growth promoting and growth inhibiting factors for specific phylotypes.

Relationship between diet, microbiota and health status

A relationship exists between diet, microbiota and health status, and indicates a role for diet-driven microbiota alterations in different rates of health deterioration with ageing. Intestinal microbiota play a role in metabolic, nutritional, physiological and immunological processes in the human body. It is involved in defence against pathogens by mechanisms such as resistance to colonisation and the production of antimicrobial compounds. In addition, the intestinal microbiota is involved in the development, maturation and maintenance of sensory and motor functions, the intestinal barrier and the immune system. Microbiota can adapt its composition to the diet, e.g. Japanese people can digest seaweed from their daily diet thanks to enzymes that their microbiota has acquired from marine bacteria.

Increase in disease-causing bacteria

In the same way, dysbiosis can manifest itself as an increase in disease-causing bacteria, a decrease in health-enhancing bacterial species and/or a reduction in bacterial species diversity. The health problems are innumerable and among the options for restoring the balance are good nutrition, probiotics and prebiotics.

Probiotics are living microorganisms (in most cases bacteria) that are similar to the beneficial microorganisms found in the human gut. They are also called "friendly bacteria" or "good bacteria". Probiotics are available in fermented foods, such as culture media.

Prebiotics are indigestible food ingredients that stimulate the growth of bifidogenic bacteria and lactic acid in the gastrointestinal tract. Typically, prebiotics consist of dietary fibres and oligosaccharides. Most of the intestinal microbiota resides in the large intestine, the main location of bacterial fermentation.

Microbiota are grouped according to plant or animal-based diet patterns. Bacterial diversity in mammals is highest among herbivores, followed by omnivores and then carnivores, and is also compositional and functionally different. 

Relationship between human health and microbiota

Research is being conducted on the relationship between human health and common bacterial taxa found in the human microbiota. Chronic diseases such as obesity, inflammatory bowel disease, diabetes mellitus, metabolic syndrome, atherosclerosis, alcoholic liver disease, cirrhosis and hepatocellular carcinoma have been associated with the human microbiota.

The dietary manipulation of microbiota through strategies that favour the growth of "beneficial" bacteria as opposed to those described as "pathogenic" is considered a potential alternative when it comes to treating or preventing the development of various pathologies such as obesity.

The intestinal microbiota exerts important metabolic activities by extracting energy in otherwise indigestible dietary polysaccharides such as resistant starch and dietary fibres. These metabolic activities also lead to the production of important nutrients, such as short-chain fatty acids (SCFA), vitamins (e.g. vitamin K, vitamin B12, folic acid) and amino acids, which humans cannot produce themselves. 

Influence of the diet

The type and amount of protein, fat and carbohydrates in the diet influence the composition of the intestinal microbiota. Fat in the diet is normally absorbed in the small intestine, and only small amounts reach the large intestine. Fat is not a primary energy source for the colonic microbiota.

Consumption of diets high in saturated and trans fats increases the risk of cardiovascular disease through the upward regulation of total cholesterol and low-density lipoproteins (LDL) in the blood. Diets rich in fat interact in various ways with the intestinal microbiota to facilitate the translocation of bacterial lipopolysaccharides that contribute to the generation of chronic inflammation.

Digestible carbohydrates are enzymatically degraded in the small intestine and include starches and sugars. After degradation, these compounds release glucose into the bloodstream and stimulate a response to insulin.

Consequently, dietary fibre is a good source of 'microbiota-accessible carbohydrates', which can be used by microorganisms to provide energy and a source of carbon. This property of fibre guarantees their designation as prebiotics, which are non-digestible dietary components that benefit health through the selective stimulation of the growth and/or activity of certain micro-organisms.

Consumption of whole grains

Diets of indigestible carbohydrates that are rich in whole grains and wheat bran are associated with an increase in bifidobacteria and lactobacilli in the intestine. This prebiotic effect on bifidobacteria has also been observed with whole grain maize, resulting in a beneficial change in the microbiota.

Consumption of other indigestible carbohydrates, such as whole grain barley, results in enrichment of the genera Roseburia, Bifidobacterium, Dialister and the species Eubacterium rectale, Roseburia faecis and Roseburia intestinalis and resistant starch increases Ruminococcus bromii and Eubacterium rectalis.

Whole grain versions of starchy foods (e.g. whole wheat pasta, brown rice) contain more resistant starch than refined versions. Therefore it has always been said that wholemeal bread is healthier than white flour bread.

 Increased dietary fibre intake has not been shown to have a bifidogenic effect but has been associated with increased intestinal microbial richness and/or diversity, especially in individuals with initially reduced diversity.

Conclusion

The diet modifies the intestinal microbiome. The beneficial or harmful effects of diets are mediated by the microbiota and depend on the identity and abundance of bacterial populations. Diets based on plants and animals have different effects on the ecology of the intestinal microbiota. A favourable microbiota produces health benefits and is achieved by diets rich in carbohydrates and low in protein/fat. The diet can be used to modulate the composition and metabolism of intestinal microbiota.

This article shows that carbohydrate intake in the form of whole wheat grains, barley, maize, millet or other cereals enriches the microbiota and thus supports our health. From a scientific point of view, we can assure that sourdough bread, one of the most consumed carbohydrates, is nutritionally a healthy and necessary food for our organism.