The study from 2015 shown people today have to eat less and exercise more than people did in the 1980s in order to maintain a healthy weight.

Authors suggested several possible explanations for these findings such as a lower resting metabolic rate in obese individuals, organic pollutants in food, the use of prescription drugs, etc. One of possible explanation is also the gut flora or microbiota – the microbe population living in our intestine.  The studies on the intestinal microbe population are revealing significant variations in gut microbiota between obese and non-obese animals and humans.

Lately, the influence of human microbiota to our health has been extensively researched and the findings are pretty amazing.  Today, it is well established that a healthy microbiota is largely responsible for individual’s overall health.

Main function of the microbiota

A main function of the microbiota is to protect the intestine against colonization by potentially harmful microorganisms. Our microbiota direct compete for limited nutrients with harmful microorganism we ingest with the food.  Breakdown of the normal microbial community increases the risk of infection, the overgrowth of harmful intestinal bacteria and inflammatory diseases.

Immune system

Our microbiota plays a fundamental role in the function of our immune system by activation of immune responses. The interaction between the microbiota and our immune system begins at birth and it is very complex.  The method of delivery (vaginal delivery or cesarian section), nutritional factors (breast or bottle-feeding), and other factors influence the development of a healthy microbiota.  Impairment in the regulation of the gut flora has been correlated with a host of inflammatory and autoimmune conditions.

Digestive system

It is necessary to mention here how the gut microbiota plays important role in digestion of food we eat.

  • Carbohydrates that escaped absorption in the small intestine and dietary fibre are fermented by the gut flora. The fermentation results in a formation of the short chain fatty acids (SCFA). Short-chain fatty acids are important for colon health because they are the primary energy source for colonic cells. This formation of SCFAs has shown health benefits, as SCFAs may reduce the risk of developing gastrointestinal diseases, cancer, and cardiovascular diseases.
  • The gut microbiota has also shown a positive impact on lipid and protein metabolism.
  • Another major metabolic function of the gut flora is a synthesis of vitamin B and vitamin K. Some bacteria in our gut flora (Bacteroides spp.) even synthesize conjugated linoleic acid (CLA) that might help reduce body fat deposits and improve immune function.
  • Microbiota is important for the absorption of dietary minerals: magnesium, calcium and iron.
  • Bile acids that are synthesized from cholesterol in the liver and secreted into the intestine are biotransformed by the gut bacteria.  Bile acids play important role in lipid metabolism. Healthy bile metabolism in the gut is important for the regulation of cholesterol balance and inflammation processes in the colon.
  • Studies have shown that the microbiota is also involved in the breakdown of various polyphenols (compounds found in fruits, vegetables and products like tea, cocoa or wine). Polyphenols are biotransformed to active compounds with help of the gut microbiota and evidence of their role in the prevention of degenerative diseases such as cancer and cardiovascular diseases is emerging.

It all sounds familiar, but…

The fact that our microbiota helps with food digestion and provide us with important nutrients may not come as surprise. This is something we know for many years. But the new findings from the recent research are quite surprising.

  • Scientists have found close links between the brain and the gut microbiota (the microbiome-gut-brain axis). Chemicals released by the activity of gut bacteria trigger the response of nerves in the gastrointestinal tract. It has also been proven that the gut and the brain communicate with each other via several routes including the vagus nerve, the immune system or the enteric nervous system. Research showed ties between autism symptoms and the composition and diversity of a person’s microbiota. Links have also been observed between the gut microbiome and brain disorders including anxiety, depression, and chronic pain. On the other hand, use of probiotics is associated with a reduction in depressive symptoms.  I don’t know about you, but I think the fact that our intestinal microbes have developed ways to shape our behaviour is fascinating!
  • As microbiota plays an important part in the function of our immune system, the new findings suggest microbiota has been implicated in several autoimmune disorders (inflammatory bowel disease, diabetes, multiple sclerosis and rheumatoid arthritis). A research study published in Nature Communications showed that people with multiple sclerosis have different patterns of gut microorganisms than healthy individuals. It is assumed that gut microbiota in patients with MS can cause the immune system to overreact to the myelin sheath if there is a corresponding genetic predisposition.  Off course, scientists will have to explore the connection between gut flora and immune system in much greater extent. Much more research needs to be done, but what if we could change the microbiota composition in these individuals by treatment with probiotics/prebiotics? Some probiotics already demonstrated benefits in the prevention of allergy, diarrhoea and improvement of symptoms in irritable bowel syndrome.
  • Research also has shown a connection between microbes living in the gut and gluten sensitivities. The findings are consistent with the theory that imbalances in microbiota could contribute to the symptoms of gluten sensitivities. Supplementation with probiotic (Bifidobacterium infantis) was shown to alleviate some symptoms associated with gluten sensitivity, but further studies have to be performed to establish safe use of probiotics in the treatment of Celiac disease.
  • Some studies found that children exposed to dogs, cats and other pets early in life are at lower risk of development of allergies. It is believed that such associations are down due to changes in child’s microbiota, as a result of exposure to bacteria from pets.
  • A study published in Nature has shown in mice that the microbiota plays an important role in post-dieting weight gain. The study implies the composition of the gut microbiota induced by obesity remains the same even 6 months after weight loss.  It is like microbes in the gut retain a “memory” of obesity. As soon as the mice returned to eating a normal diet, the gut flora sped up the body’s process of regaining weight. These findings suggest that post-dieting weight gain may in the future be prevented by altering the composition of the microbiota.

Today, there is a significant amount of brand new investigations that are used to study the complex connection between the gut microbiota and the dietary factors, environmental conditions and our health in general.

Dietary modulation of the gut microbiota

If you consider what can you do to improve your health and how to modulate your microbiota, you should apply the same principles the dietitians recommend for many, many years: eat more vegetables, fruit, whole grains, legumes, and nuts or seeds. A real food that is high in fiber, and more plant-based foods, produce more robust microbiota, with beneficial bacteria species and fewer pathogenic bacteria living in the gut.

Other dietary strategies that are available for modulating the activity of the gut microbiota are a use of probiotics (host-friendly bacteria and yeasts), prebiotics (non-digestible food ingredient that promotes the growth of beneficial microorganisms in the gut) and polyphenols (compounds found in fruits, vegetables and products like tea, cocoa or wine).



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