Growing up, I was one of those lucky kids who wasn't allergicto anything. I felt like I was invincible – while my friendswere pestered by pollen or peanuts, I was able to eat and play withreckless abandon. Childhoods like mine, however, are becoming more and more scarce . A recent study found that in 2008, peanut allergies in kids were three and a half times higher than adecade before , with similar trends occurring in a number of food allergies.Similarly, the prevalence of hay fever in developed countries hasincreased about 100 percent in each of the last three decades.It's not just allergies – other chronic inflammatorydiseases, from arthritis to asthma, continue to rise in ourpopulations.
A new paper in the Proceedings of the National Academyof Sciences suggests that perhaps the problem isn't whatwe're putting into our environment, but what we'reremoving from it: that the loss of biodiversity is negativelyimpacting our health. One of the most popular hypotheses to explain the rise ininflammatory conditions is known as the Hygiene Hypothesis , which says that our increasingly sterile lifestyle is to blamefor our allergic reactions. We now live in a world of antibacterialsoaps, instant hand sanitizer, vaccines, and antibiotics, all ofwhich have taken over the job of protecting our children from dirtand germs. Left with nothing to do, kid's immune systems geta little stir crazy, and start attacking even minor invaders likepollen with increased zeal.
But Ilkka Hanski and her colleaguesfrom the University of Helsinki in Finland suggest the HygieneHypothesis extends beyond how clean we keep our house. They putforward a Biodiversity Hypothesis, which suggests that less contactwith the nature and biodiversity is adversely affecting themicrobes on and in our bodies, leading to increased susceptibilityto immune disorders. To test this hypothesis, the research team investigated therelationship between biodiversity, allergen susceptibility, andskin microbial communities in a little over 100 randomly chosenteenagers in Finland. The kids grew up in a variety of settings,from tightly-packed villages to rural farmlands.
For eachparticipant, they measured how sensitive their skin was toallergens and what kind of microbes were living on there. Based ontheir skin's immune reaction, they classified the students asallergen-sensitive (a condition known as atopy ) or not. The researchers also roughly calculated the level ofenvironmental biodiversity where the participants lived by lookingat the amount of plant cover of their yards and the major land usetypes within 3 km of their homes, allowing comparisons between itand the participant's allergy sensitivity and skinmicroorganisms. The team found a strong, significant correlation between thediversity of a particular class of skin bacteria, calledgammaproteobacteria, and allergen sensitivity.
Though they onlyrepresented 3% of the skin bacterial community, gammaproteobacteriawere the only class that showed a significant decrease in diversityin the atopic individuals. So, to get a closer look at thisphenomenon, directly comparing the presence of differentgammaproteobacteria with levels of an anti-inflamatory marker,IL-10, in the subjects' blood. The presence of onegammaproteobacterial genus, Acinetobacter , was strongly linked to higher levels of IL-10 in healthyindividuals but not in the allergen-sensitive ones. As the authorsexplain, this suggests that these microbes may help teach theimmune system to ignore pesky allergens.
"The positive association between the abundance of thegammaproteobacterial genus Acinetobacter and IL-10 expression… in healthy individuals, but not inatopic individuals, is consistent with IL-10 s central role inmaintaining immunologic tolerance to harmless substances."Thus, the authors say, "the lack of association between Acinetobacter and IL-10 expression in atopic individuals in the present studymight re ect a breakdown of the regulatory mechanisms." How, exactly, Actinetobacter and other gammaproteobacteria influence our immune system has yetto be determined. What the authors did show is that environment aperson grows up in has a strong effect on the presence anddiversity of this group of bacteria. Since gammaproteobacteria areare commonly found in soil and on plants (including oweringplants and their pollen), it may not seem that surprising to theresearchers that the environmental diversity around a subject wasstrongly correlated to increased diversity of their skingammaproteobacteria. But what is astounding is that thisrelationship held even when the researchers stepped back and lookedat the overall connection between allergen sensitivity and thesurrounding environment; the more natural biodiversity where thekid grew up, the less likely he or she was to be sensitive toallergens. "The present results demonstrate that biodiversity can besurprisingly strongly associated with atopy." This suggests that the urban-dwelling nature of developed countriesmay be to blame for their increasing problem with inflammatorydiseases.
If so, conservation of natural spaces, including parksand other green initiatives, may be key to protecting the health offuture generations. "Interactions with natural environmentalfeatures not only may increase general human well being in urbanareas, but also may enrich the commensal microbiota and enhance itsinteraction with the immune system, with far-reaching consequencesfor public health." Since allergies cost us almost $14.5 billion annually including medical expenses, missed schooland work, and over the counter drugs , there may be a strong monetary incentive to conserve our naturalareas – if only for the sake of our health. That's noteven considering the other economic incentives for conservation, including water filtrationand storm protection, which have been estimated at over $4.4 trillion dollars per year . What all these studies tell us is that the cost of conservation isstrongly outweighed by its benefits.
Period. Reference: Ilkka Hanski, et al. 2012. Environmental biodiversity,human microbiota, and allergy are interrelated. PNAS Early Edition,doi: 10.1073/pnas.1205624109 Image of soil and hands Soil-Net.Com under a Creative Commons License. I am an expert from Toys, usually analyzes all kind of industries situation, such as wooden handmade toys , computer hunting games.
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