In my last post, I talked about how microbiome depletion results from immigrating to the United States (and subsequent dietary changes), which leads to obesity and metabolic diseases. I promised to tell you more about immigrant studies on biome depletion so today I am addressing a paper from 2 years ago in which researchers describe the effects of macrobiome (helminth) depletion in immigrants to a westernized nation.
In this case, scientists looked at the development of allergy in 126 Ethiopians newly arrived in Israel.[i] They were tested upon arrival and then, 115 of them were retested a year later. The health assessments consisted of allergy testing – and stool and blood sampling, in order to determine the presence of helminths. Anti-helminth medication was offered to all those with helminths but only 46.3% of the people chose to take it.
At baseline (i.e. when the people first arrived): most of them were positive for helminths. Of the 18 who were not, 22.2% (so 4 people) tested positive for allergies. Of the 108 who were helminth-positive, only 7 (so 6.5%) tested allergy positive. Thus, a total of only 11 people (8.7%) tested positive for allergies
Now here’s where it gets really interesting. A year later, after living in a highly-developed nation, “…a significant general increase in allergy…was observed.” 30 people (26.1%) now tested positive for allergies, as opposed the 11 of the previous year. After not only looking at allergic symptoms, but also skin prick testing for reactivity, the scientists concluded that allergic reactivity had increased in all the immigrants.
The research showed that “Helminth infection is significantly associated with low allergy and low SPT [skin prick testing] reactivity.” Even in the helminth-positive population that had chosen to not take the anti-helminth medication, an increase in allergic sensitivity was observed. There are several possible explanations for this, including the fact that lack of exposure to helminths meant they were slowly losing their helminth population as worms died off. Certainly too, other environmental factors – for example, dietary changes leading to microbiome depletion – also played a role. However, the conclusion of the paper is that the loss of helminths was definitely the major factor in the increase in allergic sensitivity.
One last note of interest: I can think of at least 1 paper in the literature that shows that multiple kinds of helminths leads to markedly higher levels of regulatory cytokines (those chemicals that turn off the inflammatory response). That finding was confirmed by this research as well: “Infection with several parasites had even lower allergy than monoinfection compared to the non infected individuals.”
Unfortunately, the research ended there. It would have been great to see what happened to those individuals allergy-wise if helminths were reintroduced. Oh well….
[i] Stein, M, Greenberg, Z, Boaz, M, Handzel, ZT, Meshesha, MK, Bentwich, Z. The role of helminths infection and environment in the development of allergy: a prospective study of newlyl-arrived Ethiopian immigrants in Israel. Plos: Neglected Tropical Diseases. 2016;10(1): e0004208. doi: 10.1371/journal.pntd.0004208.