December 9, 2016
While our understanding of the human microbiome is still in its very early stages, it has come very far in the last 10 years. New work elucidating the changing nature of gut flora from birth to childhood and throughout life reveals stages and conditions in which probiotics play different roles or may be more critical. These findings should play a role in our thinking about probiotic product design and use and will likely align with a customized approach as the research deepens.
But how malleable is the microbiome? The answer has many implications for the supplement industry.
It has been known for some time that during and immediately after birth, a baby’s gut is rapidly populated with bacteria from its surroundings, which begin to shape the microflora. Several major factors affect how healthy that microflora starts out: mode of delivery (natural birth vs. C-section), diet (breast milk vs. formula), environment (city vs. country, siblings, pets, farm animals, playing with dirt) and use of antibiotics in the first year.
The shift to solid food is another milestone for the developing flora in that additional types of bacteria are needed to help break down the foods, produce vitamins and otherwise assist metabolism. At this point, the types of food eaten make a difference for the richness and health of the flora, with the best input coming from eating a wide variety of unprocessed fruits, vegetables, grains and protein sources.
These factors have their influences during the first three years of life when the general composition of the microbiome shifts and changes easily and often. By approximately three years of age, however, the microbial profile assumes the composition of an adult. This has recently been found to be true across widely different geographical and ethnic populations, diets and lifestyles around the world. Alteration of the microbiome during those first three years, for better or worse, has the potential to profoundly affect later health and development.
After that, the microbiome cannot easily be micromanaged.
The long haul
The adult gut population appears to be largely stable for years or even decades, with 70 percent of the strains staying the same. Even following perturbations such as antibiotic use or illness, the gut eventually defaults back to what it used to be. Usually back to that age-3 composition.
It makes sense that this would happen. The body can count on having the consistent presence of certain bacteria it relies on for critical functions such as vitamin production or metabolism of carbohydrates and amino acids. It also provides the immune system the benefit that the body is accustomed to these bacteria over the long term such that an immune response is not triggered against them.
Long term changes to the adult microbiome can be effected in a few ways, however. Shifts in diet, such as eliminating wheat and sugar or modifying the balance of carbs and protein over a sustained period can change the overall composition of bacteria. Weight loss (even temporary) has also been shown to alter the strains found in the gut. And transplanting fecal bacteria from one person’s gut to another can establish a new microflora (with the eyebrow-raising effect of also carrying over the fat-or-thin weight status of the donor!).
And then of course we come to probiotic supplementation. Where can it fit in to this picture, if such a large part of the microflora seems stable?
First, it seems clear that supplementation for children 0-3 may be especially prudent, particularly for those who do not have the benefit of the factors most important to establishing a healthy microbiome. While research regarding effects on conditions such as allergies and asthma is still in preliminary stages, the body of data on strain-specific benefits is increasing. Safety assessments for this youngest population are also currently underway for several strains.
Second, for adults, it seems that the 30 percent of bacteria that are changeable over the short term can be favorably influenced. This is particularly true in the small intestine, where the microflora can change even daily, depending on things like what was recently eaten.
To the rescue
It’s also true when the bacterial population at large is perturbed. Supplementation can hasten the return to the original population or fend off the establishment of bad bacteria that cause diarrhea; each of these conditions is best served by specific strains, and our understanding of this is also growing.
In the case where the default gut population is not as healthy as it could be to begin with, supplementation can offer ongoing fortification of the gut with helpful bacteria, though this would have to be taken every day.
Currently, many things we understand about how the world of gut bacteria operates are characterized as “our best guess.” But as we understand more about their role in the body and about the benefits of individual strains themselves, we will be poised to develop more sophisticated and targeted products. So, though 70 percent of the microbiome is set at 3, the remaining 30 percent leaves plenty to work with. The category is ripe for cultivation.
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