More on the hygiene hypothesis by a science writer who has searched the literature, traveled the world and interviewed scores of scientists who attribute a rise in allergies, autoimmune disease, asthma and many other disorders in our sanitized societies to an imbalance in our immune systems.
Velasquez-Manoff writes that, until the Industrial Revolution, the human body was host to a rich microbiota of bacteria, viruses, parasites and pests. From birth, the immune system learned to respond to these fellow travelers by attacking deadly pathogens, collaborating with useful flora (such as bacteria that help digest food) and tolerating parasites like intestinal worms. With the rise of modernity came the movement from farms to cities, where smaller families are served by clean water and sewer systems. Then came antibiotics, deworming medicine, processed foods, etc.—the whole panoply of life in the developed world. Left without our “old friends,” the parasites in our guts, we now have an immune system that has turned against the body’s own cells, causing an increase in irritable bowel syndrome, asthma, eczema and a slew of other diseases that are on the rise, such as autism, diabetes, some cancers, heart disease and dementia. The problem is that the evidence to confirm the immune connection is largely based on observational studies, epidemiological associations or animal experiments, to which must be added the role of diet, genetic factors and other variables. Nonetheless, desperate patients have chosen to self-medicate with intestinal worms, including the author. To his credit, he carefully reviews this undisciplined field and reveals his own experience. The massive data he presents, the insights into the role of the gut as orchestrator of immune responses, and the revelations coming from the completion of the Human Microbiome Project should spur much-needed research in the field. Velasquez-Manoff concludes with a discussion of the clinical trials in the works to test worms in treating multiple sclerosis, autism, peanut allergies and other maladies.
A solid, up-to-date report on a growing area of scientific research.