Bill & Melinda Gates Foundation

Gut microbes are critical enablers

August 16, 2018

An inseparable part of the human body, the complement of microorganisms living within our intestine, called the intestinal microbiome, plays a critical role in directing healthy growth and development, and preventing vulnerability to childhood illness.   Research links the microbiome with better cognitive scores in one-year-old infants, and has identified brain and behavioural characteristics clustered by gut microbiota profile, in middle-aged adults.

We now know that the human gut microbiome impacts human brain-health in numerous ways, such as stimulation of the innate immune system and the production of hormones and neurotransmitters that are identical to those produced by humans.  In this way it stimulates different neurons of the enteric nervous system, thus impacting architecture of sleep, reaction to stress as well as memory, mood, and cognition.  To build physical-health, the gut microbiome allows appropriate nutrient absorption and defends the body from invading organisms.  It directly impacts the body’s immunity and metabolism and determines our response to external medication and vaccines.   The greatest load and diversity of microbial cells is believed to be within the gastrointestinal tract and any disruption in the balance of these microbes is also associated with a number of adult diseases such as diabetes, obesity, inflammatory illnesses such as arthritis, autoimmune conditions, and even psychological and neurological ailments.

Gut health is largely dependent on three factors: (i) the balance of the microbes present in the gut, (ii) the proper functioning of the gut barrier that separates microbes from the immune system, and (iii) the well-being of the gut immune system itself. When the gut barrier allows appropriate nutrient absorption and defends the body from invading organisms, it directly impacts our body’s immunity and metabolism.  It also determines our response to external medication and vaccines.  There are three main therapeutic approaches that might be used to address gut health:  food, microbes, and medicines.

  1. Food: It is critical that infants get an adequate supply of breast milk in the first six months.In addition to helping with the growth of good bacteria, several studies have shown that there is a mother-to-infant transfer of the required bacterial strains through breast milk. It is also important for gut-health that young children as well as pregnant and lactating women receive a balanced nutrition consisting of diverse ideally fresh foods with adequate protein, fat, carbohydrates, and fibre as well as other key micronutrients and bioactive molecules that help good microbes and the individual grow.  
  2. Microbes: A separate therapeutic class involves ingesting the microbes themselves, such as carefully chosen probiotics (e.g. Lactobacillus and Bifidobacterium), or more exotic healthy bacteria found only in the gut, that can help increase immune responses to oral vaccines and protect children from infectious diseases.   

  3. Medicines: A third approach involves delivering gut-targeted pharmaceuticals that act upon the lining of the gastrointestinal tract to help improve the gut’s barrier function and immune system.

Medical science is rapidly learning how to manipulate gut microbes to address underlying disease vulnerability.  There are several very promising gut-microbe-based clinical trials around the world that are evaluating interventions aimed at reversing the high rate of neonatal malnutrition and stunting. In a trial in Bangladesh, researchers are evaluating the role of rationally designed foods to repair the microbiome of 12-18-month-old children with malnutrition, in order to promote weight gain.  Another trial in Bangladesh is evaluating a carefully chosen probiotic together with a special sugar microbes like to eat, in malnourished breast-feeding 2-6 month old infants, to improve their weight gain and healthy growth. Scientists in South Africa are working with older, 18-60 months of age, children with malnutrition, to see if microbial transplants from healthy guts can restore intestinal microbiomes and healthy growth.

Despite the dramatic progress in the last two decades, infant mortality remains one of the biggest health challenges faced by the world today. Focus on the microbiome and gut are now at the cutting edge of scientific research on infant health and malnutrition. It is heartening to note that there is emerging evidence that the microbiome dramatically affects nutritional status and this approach has the potential to overturn traditional approaches. Promoting the development of healthy gut bacteria through appropriate nutritional interventions could go a long way in boosting overall health.

This article was originally published in Hindustan Times on Aug 16, 2018


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