Diabetes in the Pima Nation: Genetics, Diet, and Solutions

As Brenda Davis has shown in her study of the natives of the Marshall Islands, a non-native diet can be a major factor in the dramatic increase of diabetes cases within an indigenous population. Other researchers, such as Carolyn Smith-Morris, have focused on inherent biological factors that may also play a role. This paper applies the findings of both Davis and Smith-Morris to the Pima people of southern Arizona. The Pima have long suffered from diabetes, as Smith-Morris recounts in her study of the people. The question is: why?

While Smith-Morris points to genetic causes for the tribe's diabetes, there is also evidence that dietary and lifestyle changes are a contributing factor in the modern era. This paper argues that, because of biological factors and a non-native diet, the Pima are prone to diabetes, and examines what steps can be taken to reduce that risk for this indigenous people.

The Pima are a tribe of Native Americans who today live in central and southern Arizona. They were first visited by Spanish missionaries near the end of the 17th century and introduced to Western culture, tools, livestock, and crops such as wheat (Myers, Gryder). While this contact was largely infrequent for many decades, by the middle of the 19th century it had increased considerably — the American frontier had expanded, new territory was being absorbed into the United States at a continuous rate, and the Gold Rush brought more and more speculators to the region.

The American government never held a policy of true patronage toward the Native American tribes, instead choosing to relocate them to settlements — those who were not eliminated in warfare — or to assimilate them into American life. With the Pima, the latter was attempted; yet in the post-war period the Pima pushed for autonomy and a return to their own way of life (Brody). Today, they are recognized by the U.S. government as a Native American tribe (Myers, Gryder).

In spite of their independence, the Pima have been impacted by Western culture to a large extent — most notably through changes in their agricultural styles and dietary habits. Like many other indigenous groups around the world, the Pima have felt the effects of globalization and industrialization, which have allowed Western-style foods and customs to penetrate virtually every culture on the planet (Brody). It is therefore no surprise that even among the Pima, Western customs have been absorbed, regardless of the tribe's desire to return to traditional practices. The environment in which they live, the crops they can grow, and the livestock that are now part of their native land have all been transformed by the infusion of Western culture over the course of many generations.

What makes the Pima stand out among any other group in the world is the fact that they have the highest rate of diabetes incidence on earth. As Stephan Guyenet notes, nearly 40% of the Pima population is diabetic. Genetic studies on the population have shown that the Pima gene pool is particularly isolated in terms of genetic variance. Leslie Baier and Robert Hanson show in their study that the Pima "have limited genetic and environmental variability," which makes them ideal subjects for identifying the causes of diabetes (1182). The fact that their prevalence of diabetes is the highest among all populations in the world gives researchers a unique perspective on the plight of the Pima (Baier, Hanson).

In the Pima population, there is little European intermixing, so the genetic makeup of the tribe is still very much consistent with its indigenous past (Baier, Hanson). The main type of diabetes exhibited by the Pima is Type 2, the most common type throughout the world. While Baier and Hanson indicate that the onset of diabetes among Pima tribal members is "familial" rather than strictly "genetic," other researchers suggest that biological factors — not just lifestyle factors — are also predictors of the disease (Baier, Hanson 1182; Billings, Florez). Baier and Hanson argue that the evidence for diabetes being an entirely genetic disease is scant, while Billings and Florez contend that findings have at least identified genetic disorder traits that coincide with diabetes.

In their 2010 study, Billings and Florez identify genomic issues in Type 2 diabetics, pointing to "novel pathways" that suggest the disease is rooted in "fundamental biology" — specifically, a "β-cell dysfunction" (Billings, Florez 59). Genome mapping has allowed researchers to identify which regions of the genetic makeup are responsible for affecting Type 2 diabetes. Yet, as Baier and Hanson argue, while genetic flaws may now be apparent, the actual causes — that is, heritability — remain less clear. The genomic dysfunctions are evident, but whether their origin is biological, environmental, or familial is not. The Pima are thus an especially attractive group for researchers, as their prevalence rates and genetic lineage offer an ideal starting point for study.

Carolyn Smith-Morris begins her study of the Pima and their struggle with diabetes by turning to the people's own narratives — stories collected from time immemorial about being haunted by an evil spirit that plagued Pima children in particular. Smith-Morris's investigation of Pima culture reveals that this people has been affected by diabetes for many centuries, which is why she believes the issue to be rooted at least partially in genetics. Baier and Hanson, however, point to familial causes, and the distinction is important.

Genetic causes suggest that the disorder is biological — that there is no way to guard against it short of altering the genomic structure. Familial causes suggest that the disorder is social — passed from generation to generation through learned behaviors demonstrated by family members. Both may be true. There is as yet no substantive evidence to prove beyond a reasonable doubt that Type 2 diabetes is wholly genetic or wholly the result of poor environmental, social, or dietary and exercise conditions.

The long history of the Pima indicates that they have a genetic or at least familial predisposition to diabetes, as both Baier and Hanson and Smith-Morris show. Smith-Morris recounts the various narratives surrounding the evil spirit that preyed on Pima children, as told in the people's own words. According to Smith-Morris, the problem of diabetes for the Pima could stretch back a millennium: