One of the ways in which immigrants to the United States acculturate to their new surroundings is by changing their eating habits. Modern US diets tend to differ from traditional diets in ways that may contribute to disease risk. Dr. Margarita Santiago-Torres, a recent Fred Hutch Post-Doc now at the University of New Mexico, along with Dr. Chris Carlson and colleagues in the Public Health Sciences Division, sought to evaluate whether differences to metabolic response to such diets may differ according to genetic ancestry. As recently reported in the European Journal of Clinical Nutrition, the authors found a modest interaction between proportion of indigenous American genetic ancestry and metabolic response to these different diets.
The thrifty gene hypothesis suggests that certain populations may be evolutionarily adapted to benefit from various components of traditional diets. Traditional Mexican diets are usually high in fruits and vegetables, and complex carbohydrates and legumes rich in dietary fiber. In contrast, US diets are usually high in processed foods, refined carbohydrates, added sugars, and low in plant foods. Migrating from one diet to the other may thus create a situation where modern social changes are at odds with historic biological expectation. Said Santiago-Torres, “When a diet high in energy-dense and nutrient-poor foods is superimposed on persons with a “thrifty genotype” who are evolutionarily adapted to diets high in legumes and complex carbohydrates, it may lead to an abnormal metabolic response that favors adipose deposition and numerous health risks. Thus, ancestral genetic characteristics likely have an important role in metabolic response to specific dietary patterns and subsequent health risks.”
Santiago-Torres and colleagues had previously shown that the traditional Mexican diet improved insulin sensitivity, and reduced circulating concentrations of IGF-1 and IGFB-3, compared to a standard US diet (see reference). Using a randomized crossover feeding trial design, 58 first- and second-generation Mexican immigrant women consumed either a traditional Mexican or commonly consumed US diet, waited a month then switched diets. To estimate how genetic ancestry might impact this metabolic response to these diets, the authors genotyped 214 ancestry informative markers (AIMs) in these women. These markers were then used to estimate the proportion of each individual’s African, European, or Indigenous American ancestry (see figure).
The authors compared metabolic response according to tertiles of proportion of Indigenous American ancestry. Compared to the US diet, the traditional Mexican diet tended to reduce levels of several biomarkers related to metabolic disease, such as glucose, insulin, IGF-1, IGFBP-3, and HOMAIR, among women in the middle tertile of Indigenous American ancestry (45-62%). Said Santiago-Torres, “These findings suggest that genetic ancestral background may have a role in the metabolic response to specific dietary patterns kept or adopted by Mexican immigrants that can lead to future risk of chronic disease and certain types of cancer.” Though more research is needed, “these findings can inform future dietary interventions and dietary recommendations relevant to this minority population who could benefit from following a traditional Mexican dietary pattern.” Such findings may be particularly relevant for underserved minority populations, who tend to be disproportionately affected by diseases such as diabetes or late-stage aggressive breast cancer.
The authors plan to further evaluate these genetic and metabolic relationships to dietary patterns outside of controlled feeding studies. Said Santiago-Torres, “there is still a need to progress these findings and implement effective dietary interventions to address poor eating and promote sustained behavior change in underserved communities. We are in the process of designing and implementing behavioral dietary interventions to test whether adhering to traditional Mexican diets compared to following healthy US diets can be effectively adopted and maintained by individuals of Mexican descent in ‘free-living’ conditions. Findings from these studies will inform future dietary recommendations and dietary interventions relevant to this minority group, who comprise the largest growing immigrant population in the US.”
Also contributing to this project from the Fred Hutch were Drs. Jean De Dieu Tapsoba, Mario Kratz, Johanna Lampe, Kara Breymeyer, Lisa Levy, Xiaoling Song, Ching-Yun Wang, and Marian Neuhouser.
Santiago-Torres M, De Dieu Tapsoba J, Kratz M, Lampe JW, Breymeyer KL, Levy L, Song X, Villaseñor A, Wang CY, Fejerman L, Neuhouser ML, Carlson CS. Genetic ancestry in relation to the metabolic response to a US versus traditional Mexican diet: a randomized crossover feeding trial among women of Mexican descent. Eur J Clin Nutr. 2016. doi: 10.1038/ejcn.2016.211.
Santiago-Torres M, Kratz M, Lampe JW, Tapsoba Jde D, Breymeyer KL, Levy L, Villaseñor A, Wang CY, Song X, Neuhouser ML. Metabolic responses to a traditional Mexican diet compared with a commonly consumed US diet in women of Mexican descent: a randomized crossover feeding trial. Am J Clin Nutr 2016; 103(2):366-74. doi: 10.3945/ajcn.115.119016.
Funding for this study was provided by the National Cancer Institute, NIH.