Medical anthropology: Cannibalism, Flying Foxes, Absinthe and white bread: the cultural basis of neurological disorders

Townsend Letter for Doctors and Patients, Nov, 2003 by Tim Batchelder

Multiple Sclerosis, Latitude and Evolution

Finally, as part of my current work in medical communications, I assist patients with MS and frequently learn of adverse events among patients while on conventional medications for this disease. Fortunately I recently came across some research on the evolution and geography of MS that may be of interest. In particular it appears that MS is strongly correlated with living at higher latitude. Hammond et al. (2000) documented that British and Irish immigrants to Queensland, Australia, had a striking 75% reduction in their risk of developing multiple sclerosis when compared with that of natives in their home countries. Sunlight intensity, and vitamin D synthesis, decreases with increasing latitude (Holick 1995) and additional studies support the concept that vitamin D supply may be a protective factor for MS. It is also interesting that the nadir in vitamin D supplies correlates with both the peak of MS lesion activity in German MS patients (Auer et al. 2000) and the peak of MS disease onset in Switzerland (Wuthrich and Rieder 1970). In addition MS is closely tied to consumption of modern foods, which are incompatible with our genetic heritage (see previous columns.) MS occurrence correlates well with the consumption of dairy products, glutenous grains and saturated fats. For example MS is almost five times as common on the Canadian Prairies as it is in the fish-eating areas of Newfoundland. Certain foreign proteins have a molecular structure similar enough to self-proteins that the immune system of some genetically susceptible individuals confuses self-proteins with the foreign ones. In MS the immune system attacks central nervous system tissues because, having been activated by a foreign protein, it mistakes the CNS self-proteins for foreign ones (molecular mimicry). Certain food proteins resemble both self and viral proteins and have the potential to cause molecular mimicry. Thus, it is possible that MS is caused by foods recently introduced into the human diet that contain proteins that closely resemble those in the human central nervous system. Other studies show that proteins derived from wheat, soy and dairy cause Type 1 diabetes.

Conclusions

From the above examples one can readily see how dietary and environmental factors can contribute to neurological diseases in some unusual ways. From pre-industrial disorders like kuru to MS in modern societies, cultures have always had to address neurological diseases that quite often derive from their own practices, rather than uncontrollable "aliens from Mars" or their equivalent, the errant gene. And many times what we consider to be self-inflicted neurological disorders may be perfectly acceptable conditions to those afflicted as was likely the case with Van Gogh and possibly among the South Fore and Chamorro people. Ultimately it is the process of understanding these disorders from the patient's perspective as anthropologists do that leads to these discoveries and eventually to safe and effective treatments.