The Secret World of Your Gut Microbiome
In recent years advances in technology have allowed scientists to delve into the mysteries of the human gut microbiome with unprecedented speed and precision. And that's significant, because it's allowing us to understand what kinds of microbes are living in and on us, where, and in what numbers, as never before. Given that microbes—bacteria, fungi and viruses—outnumber our own bodies' cells by ten-to-one, one could argue that we are, in a very real sense, "superorganisms" composed of vast, diverse communities of creatures all living more or less in harmony.
It's hard to over-emphasize the importance of this emerging and transformative new picture of the human body. We are not alone. Not by a long shot. We are, in fact, not a collection of organs and cells so much as we are a collection of intimately interconnected communities of diverse species, all working together towards a common goal. Namely, to live long and prosper.
For far too long, we've viewed the microbes living in the gut—called the microbiome—as more or less inconsequential. But that view is flat wrong, and the sooner we realize it, the better we will be able to harness this new understanding to benefit longterm health. The indiscriminate use of antibiotics, for example, may have severe unintended consequences, to the extent that it interferes with the normal, healthy makeup of the microbiome.
A picture is emerging that suggests that having the right microbes—in the right areas of the digestive tract, in the right amounts—is linked to robust health, good nutrition, good mood, healthy body weight and other benefits. Some beneficial microbes are encouraged by certain foods, for example, while others are discouraged. Conversely, eating poorly, taking antibiotics, getting too little exercise, ingesting toxins— all of these behaviors affect the microbiome, sometimes adversely. Killing off beneficial bacteria creates room for potentially disease-causing bacteria to crowd in and take their place.
Probiotic foods, such as yogurt and kefir, contain live, active microbes capable of colonizing and thriving in the specialized environments of the human digestive tract. Eating these foods can help keep the gut microbiome healthy and balanced. And that could benefit everything from immune system function, to mood and the tendency to gain weight.
Prebiotics are complex carbohydrates, mostly from plant foods, that many of these bacteria thrive on. Conversely, many of the most beneficial species are thwarted by too much dietary sugar. So you not only need to avoid indiscriminately killing off beneficial gut bacteria with antibiotics—you also have to keep them happy and healthy with the right foods. In return, they will literally help keep you happy and healthy.
In fact, a fascinating new study has examined the effects of daily activities on the makeup of an individual's microbiome. Among other things, it showed that what we eat from day to day quickly affects the makeup of the bacteria thriving in the gut. Consuming dietary fiber was linked to greater numbers of gut microbes that are known to foster good health. Eating citrus fruits, for example, encouraged the growth of a kind of bacteria that is believed to be protective against inflammatory bowel disease.
Future studies will attempt to determine how different microbial populations affect the immune system in detail, and which foods or lifestyle behaviors may encourage a microbiome that's most consistent with a healthy immune system. But there's not need to wait for the results. It's already clear what works: keep eating plant foods, avoid sugar, and consume probiotic foods or supplements regularly if you must take antibiotics.
Lawrence A David, Arne C Materna, Jonathan Friedman, Maria I Campos-Baptista, Matthew C Blackburn, Allison Perrotta, Susan E Erdman, Eric J Alm. Host lifestyle affects human microbiota on daily timescales. Genome Biology, 2014; 15 (7): R89 DOI: 10.1186/gb-2014-15-7-r89