Has Technology Made Us So Clean That We’re Sick?
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In Riddled with Life, Marlene Zuk describes our relationshi
Exactly what is it about early stimulation by bacteria, viruses, or other
parasites that kee ps the immune system calm in the face of harmless entities like pollen or ones own intestinal cells? Obviously the analogy of immune system cells being like bored unem ployed workers that make mischief on the rest of the body is just that, an analogy, and even the most anthro pomor phic among us sto ps short of assigning personality traits to bone-marrow products. The more accurate answer seems to lie in a characteristic of the immune system. Part of our res ponse to foreign invaders of the body is mediated by a kind of white blood cell called a T cell. The T cells come in a variety of ty pes, including killer T Cells and hel per T cells. The hel per T cells in turn are also divided into two ty pes, called Th-1 and Th-2. The Th-1 and Th-2 res ponses are res ponsible for protection against different things, with the former concerned with bacterial and viral diseases and the latter with infections by worms and other large parasites. Each ty pe of hel per T cell produces a different set of chemical messengers used to regulate inflammatory res ponse like tissue swelling and the production of mucus. These chemicals interact with each other and kee pthe entire system in balance.
In countries with scru
pulous hygiene, where children are vaccinated and antibiotics are widely administered, the low level of Th-1 stimulation results in an increase in the Th-2 res ponse. These Th-2 res ponses trigger an exaggerated mucus production and contraction of muscles in the airways, which can in turn cause allergic diseases and asthma. In countries where bacteria, worms, and other pathogens are abundant but vaccination and antibiotic levels are low, the Th-2 res ponses are activated, but they are regulated by re peated cycles of infection and inflammation, with the inflammation countered by natural antiallergic reactions. Thus they rarely escalate out of control as much as Th-2 res ponses in peo ple from the industrialized areas. The immune systems of peo ple from less develo ped countries still res pond physiologically to allergens like pollen or house dust mites, but the peo ple do not go on to develo pa disease. It is as if the Th-2 arm learns to recognize an innocuous but foreign substance for what it is, and has a blasé “been there done that” reaction to it, rather than s piraling into a panicky cycle of swollen tissue and dri p ping glands. [pp. 46-47]
Where technology introduces a
So that the cure not be worse than the disease,
Much more common than Crohn's Disease are stomach ulcers. The Nobel Prize in medicine went to the doctors that identified the bacterium Helicobacter pylori as responsible. Stress might exacerbate stomach ulcers, but the bacterium were the cause, allowing us to take antibiotics, kill the H pylori, and return to our stressful lifestyles. Not so fast! A 2007 study showed that H pylori helps to protect us against asthma and may play an important role in the development of the human immune system, preventing immune hyperreactivity. H pylori may be joining the legion of life that technology enables us to render extinct:
The key point, says Dr Blaser, is that H pylori colonization is the default human state of affairs, but it's a default position we're fast drifting away from. "About 10% of the US population now has detectable H pylori colonization. I was just in Sweden and Germany, where I'm told the figure is less than 5%. The proportion in the developing world is over 50%, and just a few generations ago the levels in our own societies were 70, 80, even 90%. So H pylori is disappearing really fast, and this disappearance is almost certainly mirrored in other microorganisms we can't detect as easily."
I am a
I will blog more on this later, as I have been reading books on chemicals and disease. Perha