By Gopi M.K.
We humans could be alone, but are never alone. Our bodies are continuously bathed with swathes of microbes that we represent a vast abode of several ecosystems.This information forms the basis for the human microbiome project- an exciting enterprise aimed at exhaustively detailing the microbiota in different niches in our body. Since its inception three years ago, novel facets on the roles of gut-resident bugs have been unraveled. While a few answers regarding the microbiome have been found, the offshoot of the work is even more exciting.Several interesting questions have sprung up, which from a nutritional standpoint, could hold great significance and promise when answered.
Human intestines are swarming with trillions of bacteria; their total number estimated to be ten-fold higher than the total cell number in their hosts.Their existence is a classic example of mutualism. Our diet provides them the essential nutrients for their survival while they help us digest polysaccharides from plants. Additional outcomes of our complex interactions with them are now no longer a black box. After the birth of an infant from the confines of the sterile environment in the womb, their gut is seeded with microflora. The kind of microbes in the gut could have far-reaching consequences in shaping their overall health than mere digesting the indigestible. The gut commensals are critical for the development of immune system and as a corollary, our ability to combat pernicious pathogens is effectively compromised in their absence. Molecules from gut microbiota have been shown to enhance immune cell functions to combat Staphylococcus aureus and Streptococcus pneumoniae. Gut bacteria are also indispensible for controlling inflammation by modulating the repertoire of inflammatory and immunosuppressive cells. Bacteroides fragilis has been shown to prevent gut inflammation caused by Helicobacter hepaticus. Thus it appears that collaboration between the host immune system and gut microflora has evolved to protect both the parties against invading pathogens and to maintain immune homeostasis.
The composition of gut bacteria as well as their genetic makeup is shaped by the kind of food we ingest. A novel enzyme glycoside hydrolase is present in the genome of Bacteroides pleibus present in the guts of Japanese individuals but not in their US counterparts. It has been concluded that these genes could have been acquired from the red algae used to wrap sushi, a leitmotif in the Japanese diet. The diet- gut bacteria nexus and their role in disease development could provide clues regarding the prevalence of certain diseases in different population cohorts. Eg. unlike Asian or African populations, increased incidence of Crohn's disease, type I diabetes, and multiple sclerosis has been documented in developed Western countries. Intake of highly-processed, hyper-hygienic diet in these industrialized societies could be skewing the composition of different bacteria in the gut leading to morbidity.
The obesity epidemic in the Western hemisphere further bolsters this notion. The gut microbe composition in obese mice has been found to be strikingly different from lean mice, which were also shown to fatten up when given certain gut-residing bacteria. The microbiome of obese individuals from developed countries could be skewered, perhaps by diet and increased use of antibiotics to result in inflammation and disease. However, it is still a chicken-egg conundrum and is unclear if obesity alters the gut bacterial architecture or it is the other way round. The benefits of gut flora however, are not set in stone. The role of gut bacteria in converting high-fat diet in to trimethylamine N-oxide, a harmful metabolite that causes increased plaque buildup in arteries to ultimately result in atherosclerosis and other cardiovascular diseases has recently been reported. At this juncture, identification of specific gut bacterial species that confer benefit and ways to improve their number is perhaps an enticing prospect and tremendous challenge. Identifying foods and probiotics that promote the development of a healthy microbiome composition in the gut could further enhance our overall health. The future is not so far away when we would be encouraged to consume food that would nurture the bacteria in our guts. Satiate the bug in you (not just yourself!) for a better healthy you.
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