WHY DIRT CAN BE GOOD FOR YOUR KIDS 

By: Nadir Mahmood

How often do we see our kids playing at a park or in the yard, their faces covered in dirt, and their hands scooping handfuls of the earthy soil into their mouths? As parents, we’ve been trained to run to their aid and quickly pull out any chunks of dirt from their mouth with our fingers and wipe off their brown-strained hands with soap and water or a wet wipe.  It’s a natural response to what we’ve been taught all our lives – dirt contains all kinds of things we associate as bad for us, especially those nasty little germs. Bacteria have long been associated as bad organisms, ones that spread through schools and communities like wildfire causing coughs and colds and making parents worry about how long their child will be out of school while he/she recovers. It is true, many strains of bacteria are the source of infections. This is something that we’ve known for over 50 years and in fact, the discovery of penicillin in 1928 changed modern medicine forever. The advent of antibiotics has led to a decrease in mortality rates, especially in infants. Our understanding of hygiene has also helped curbed many bacterial infections that used to afflict mankind. Antibiotics were a silver bullet that swiftly killed off those pesky invaders and allowed us to get back to normal health within a matter of days. Or do we really get back to “normal”?

What is the microbiome?

In the last ten years, scientists have made amazing progress in understanding the role that bacteria play in disease but not in the way that you might think. Research has shown that the bacteria that live in our stomach, on our skin, in our mouths, and on genital surfaces play a critical role in preventing disease. This collection of bacteria, known as the microbiome, can constitute up to 3 % of a person’s total body weight. In fact, bacterial cells outnumber our cells by a factor of 10 to 1 and there are a hundred more bacterial genes in our body than there are human genes. How did this happen? How did we become infested with these germs and what are they doing to us?

We know that bacteria were around long before humans and as we evolved as a species, they co-evolved with us. Earth scientists have been studying soil and marine bacteria for a long time and have uncovered species that play important roles in maintaining a balance in their environment by producing nutrients for other bacteria and for other organisms that inhabit those ecological niches. They can even affect the growth of other bacteria in these communities, thus controlling the overall behavior of marine or soil environment in which they reside. When a major shift in the bacterial community occurs in these ecologies, this has a profound effect on the whole ecology such as changing the ability of a plant to grow or even changing the marine life located in proximity to the bacteria. What does this have to do with people, and especially with infants? Well, our relationship with bacteria is the same. When major shifts occur in the gastrointestinal microbiome, it can lead to a multitude of ailments ranging from diarrhea, inflammation, and even altered glucose response and insulin sensitivity.

What do we know about microbiome and infant health?

Vaginal delivery vs. C-section

It is understood that the gastrointestinal tract of a normal fetus is sterile and that when a baby is born, the bacterial community from the mother and the surrounding environment is passed down to the child. In fact, studies have shown that there are large differences in a newborn’s gut microbiome depending on whether it was born via vaginal delivery or C-section. Most researchers believe that the mode of delivery plays an important role in a child’s development as this crucial relationship between bacteria and the immune system needs to be nurtured early in life and as such, there is concern that those children delivered by C-section may be more susceptible to developing certain ailments as they grow up.

Another important insight into how the microbiome controls a child’s development is the source of nutrition. The development of a healthy gut community is dependent on providing the bacteria with fuel, known as ‘prebiotics’ in the form of human milk oligosaccharides (HMOs). HMOs are found in breast milk and allow certain bacteria to grow and thrive. Over time, the composition of the HMOs in breast milk changes and as such, the bacterial community changes as well, which in turn allows for the development of new functions in the infant. This is a complicated process but what we do know is that feeding infants with breast milk early and for several months or even a year has a profound effect on the development of the microbiome – one that is not seen when infants are fed formula. Formula lacks these critical HMOs and thus far, nobody has successfully replicated all of these molecules in a lab and added them as supplements to formula. Several nutrition companies and leading academic researchers are working on this so that those mothers who have no choice but to feed their children formula, can rest assured that their babies are getting the same important nutrients as if they were breast-fed. This has become particularly important as studies are now telling us that formula-fed babies have a higher risk of developing necrotizing enertocolitis as well as allergies and asthma. Some researchers believe that the differences in how the baby’s GI tract develops as a result of being colonized with a formula-fed bacterial community may even lead to increased risk of metabolic disorders. While many of these studies are very recent and those that are ongoing will take several more years before we know what the consequences of formula vs. breast milk truly are, there is enough evidence already out there to suggest that breast milk is indeed special and important for a healthy life.

What does this mean for moms?

As with any growing scientific field, microbiome research is providing us with a new lens with which to examine health and disease. People have already been thinking about ways to improve their health through the microbiome. Probiotics are routinely found in natural food stores and of course, most yogurts are loaded with bacteria. However, whether or not these sources of bacteria provide any beneficial effect is yet to be demonstrated in a controlled scientific study. There are many anecdotes of individuals having improved GI health after eating probiotics but the clinical evidence is still lacking. In terms of infant health, there are published and ongoing studies on the effects of probiotics on the development of various diseases but again, the results are mixed. Many doctors tell parents to give their child a probiotic if it needs a course of antibiotics but whether this truly helps maintain intestinal health is unclear. One theme that is emerging is that more exposure to different sources of bacteria early in life is important and this bacterial diversity can provide long-term benefit. So lets try to nurture our fellow travelers and allow them to.

Nadir Mahmood is the Director of External Alliances at Second Genome and has a PhD in pharmacology from UT Southwestern.