Isotopic consequences of consumer food choice: Hydrogen and oxygen stable isotope ratios in foods from fast food restaurants versus supermarkets Lesley A. Chesson a,b, * , David W. Podlesak a,b , Brad R. Erkkila a,b , Thure E. Cerling a,b,c , James R. Ehleringer a,b a Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA b IsoForensics, Inc., 423 Wakara Way, Suite 205, Salt Lake City, UT 84108, USA c Department of Geology and Geophysics, University of Utah, 135 South 1460 East, Salt Lake City, UT 84112, USA article info Article history: Received 27 February 2009 Received in revised form 4 June 2009 Accepted 27 July 2009 Available online xxxx Keywords: Stable isotopes Hydrogen Oxygen American diet Fast food Supermarket abstract We investigated geographic trends in the isotopic composition of the modern American diet, purchasing paired food items from fast food restaurants and supermarkets across the USA. We observed large ranges in d 2 H and d 18 O values, suggesting variation in the region-of-origin for beef, wheat, and potatoes. Mean restaurant meal d 2 H and d 18 O values (114 and 22.6‰, respectively) were similar to supermarket values (111 and 22.1‰, respectively). There were no correlations between restaurant beef and local tap water isotope values but significant correlations between supermarket beef and water (d 2 H beef = d 2 H water  0.19115‰ and d 18 O beef = d 18 O water  0.17 + 14.8‰) suggesting regionality in the source of beef available to supermarket patrons. We observed no correlations between the stable isotopic composition of carbohydrates and local tap water. Understanding regional differences observed in some foods but not others will help refine parameters in models used to explore human movements in anthro- pological, archaeological, and forensic studies. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Modern Americans dine at a continental table, eating nationally distributed foods which are often produced in non-local (to the consumer) regions of the USA (Leff, Ramankutty, & Foley, 2004; Monfreda, Ramankutty, & Foley, 2008). The result can be a ‘‘food footprint” which is larger than that of a generation ago (Gerbens- Leenes & Nonhebel, 2002). For example, residents of North Carolina and Utah can have simultaneous access to California strawberries and Florida oranges, despite the large geographic distances be- tween the two purchase locations and between the purchase loca- tions and food production regions. While recent popular literature has championed locally-produced foods (Kingsolver, Hopp, & King- solver, 2007), the convenience and price of mass-produced items widely available in fast food restaurants and supermarkets (Jeka- nowski, 1999; Jekanowski, Binkley, & Eales, 2001) are likely to pre- vent any real change in American dining habits in the near future. Recent advances in stable isotope analysis have made it possible to investigate the region-of-origin claims of goods and materials. These investigations exploit predictable variations in the stable isotope ratios of hydrogen (d 2 H) and oxygen (d 18 O) within the glo- bal water cycle, which are subsequently incorporated into the plants and animals that we eat each day. The stable isotopes of water vary across continents, with high latitude, inland, and cooler regions being relatively depleted in the heavy isotopes of hydrogen and oxygen; in contrast, low latitude, coastal, and warmer regions tend to have water that is enriched in these heavy stable isotopes (Bowen, Ehleringer, Chesson, Stange, & Cerling, 2007). As plants incorporate local water isotopes, these signals are then propagated through subsequent trophic levels in the food web. The spatial dis- tributions of water d 2 H and d 18 O values have thus been success- fully used to discern the geographic origin of goods such as beef (Heaton, Kelly, Hoogewerff, & Woolfe, 2008; Nakashita et al., 2008), cheese (Camin et al., 2004), lamb (Camin et al., 2007), and wine (West, Ehleringer, & Cerling, 2007). Due to consolidation within American food supply chains, food purchased in two geographically disparate regions of the USA could have similar d 2 H and d 18 O values, as seen in supermarkets in Alaska and New York (O’Brien and Wooller, 2007). Ehleringer et al. (2008) capitalised on the stability of US food sources, assum- ing constant d 2 H and d 18 O values for dietary input in a process- based model predicting drinking water stable isotope ratios from modern American human hair d 2 H and d 18 O values. The authors noted, however, the model was sensitive to the fraction of conti- nentally- versus locally-derived food in an individual’s diet and 0308-8146/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2009.07.046 * Corresponding author. Address: Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA. Tel.: +1 801 581 8917; fax: +1 801 581 4665. E-mail address: chesson@biology.utah.edu (L.A. Chesson). Food Chemistry xxx (2009) xxx–xxx Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem ARTICLE IN PRESS Please cite this article in press as: Chesson, L. A., et al. Isotopic consequences of consumer food choice: Hydrogen and oxygen stable isotope ratios in foods from fast food restaurants versus supermarkets. Food Chemistry (2009), doi:10.1016/j.foodchem.2009.07.046