Sounds a little bogus, right? It actually makes perfect sense! Consider for a moment the fact that human parasites, such as parasitic worms, have evolved alongside us throughout most of human history. Such enduring symbiotic relationships would have to have affected the way each organisms' bodies functions on at least some minor level. If a population has been carrying a particular intestinal parasite for generations, it would only make sense for that population to eventually develop bodies that either (A) find a way to rid themselves of their parasites or (B) find a way to coexist with their parasites.
It seems that as far as our hookworm friends are concerned, (B) was the body’s choice for many human populations. Hookworm infections were once notoriously bad in the southern part of the United States. Thanks to John D. Rockefeller, hookworms were essentially eradicated in the south, leading to healthier, more productive citizens who could now enjoy a much better quality of life. While this monumental public health achievement was vital to re-energizing the southern economy, it didn’t go completely without consequence. Generations later, people whose bodies had adapted to deal with the commonly occurring hookworm infections began to develop health issues that ranged from mild allergies to severe intestinal diseases.
The causes of such issues were not linked to a loss of hookworms in the body until much, much later. Research has now shown that having hookworms within your body causes the body to launch an immune response that increases the amount of mucus put out by your intestines. This response is vital to suppressing chronic diseases such as ulcerative colitis, celiac disease, and Crohn’s disease.
For a more technical description of how the immune system works with (or without depending on your perspective) parasites, see one of my older posts titled: Helminthic Therapy. That post does a great job dealing with the creation of regulatory T cells and the interplay of interleukin genes with helminths and autoimmune diseases. Here’s the link if you are interested:
Anyway, back to the discussion at hand. So by losing friends, like our hookworms, we have caused our immune systems to freak out on our bodies. This immunological temper-tantrum has put us at greater risk of developing autoimmune issues such as the intestinal issues mentioned previous, but also for diseases such as asthma, hayfever, multiple sclerosis, and various food allergies.
Not to fear, however, for as they say, knowledge is power. By knowing that these diseases may be brought on by a lack of something, or someone (which I suppose is more correct), it is easier to treat patients that deal with such issues. Helminthic therapy is one of the more exciting mechanisms we have developed to restore our lost friends and their benefits. The long description of this can, again, be found on a previous post. (See above link.) The short definition is that the patient is treated for such diseases by purposefully reintroducing a small, easily controlled, number of “parasites” into their bodies to elicit the proper immune response that will inadvertently treat their disease. Scary as this sounds, it is a virtually harmless, painless treatment that has astoundingly positive results for people who suffer from some of the most brutally painful autoimmune diseases.
There are probably many more examples of how we have put ourselves at risk for various health issues by trying to make ourselves healthier. Paradoxical as it may seem, such is the beauty and mysterious nature of the ever-evolving field of medical science. The Lost Friends Theory is actually a subset of a broader hypothesis called “The Hygiene Hypothesis” which extends this concept to bacteria and viruses.
Moral of the Story
Things are rarely as they seem. It is important that we don’t allow our bodies to be ransacked by preventable diseases, but it is just as important that we don’t wipe out organisms that our body depends on to keep itself healthy. The idea of parasites living inside one’s body is a terrifying thought. This perception is a result of decades of movies and books that attach a stigma of what Carl Zimmer calls, “A precise horror” to the concept of parasitism. As rational human beings, we sometimes need our perceptions to be challenged. Such is how we better our chances of unlocking the mysteries of the biological universe. Perhaps it would be good for us to see the often unrealized potential of parasites by looking at these creatures in a less frightening light. Maybe if we start seeing them for what they really are, not agents bent on bodily domination, but rather just as organisms trying to complete their own small circle of life, then we would be able to more easily digest the idea of them being useful, and invited guests. After all, we are ourselves a great conglomerate of a multitude of organisms working together to form what we call our individual selves. We are positively teeming with bacteria and invisible mites that all add up to the complexity of who we are. So why not make a little room in our bodies for organisms that may alleviate our autoimmune problems if we face them? Why not reconnect with our lost friends when needed?