by revere, cross-posted at Effect Measure

Half of all restaurants in the United States are fast food restaurants. They do $100 billion worth of business a year (that’s one seventh of a Bailout, a new unit of expenditure). A lot of the fast food is in the form of beef (hamburgers), chicken (sandwiches, tenders or nuggets) and french fries. A new paper in the Proceedings of the National Academy of Sciences (PNAS, familiarly known in the trade as “penis”) uses stable isotope analysis to trace the input materials in three large fast food chains. The results can be summed up in one word — corn:

We used carbon and nitrogen stable isotopes to infer the source of feed to meat animals, the source of fat within fries, and the extent of fertilization and confinement inherent to production. We sampled food from McDonald’s, Burger King, and Wendy’s chains, purchasing >480 servings of hamburgers, chicken sandwiches and fries within geographically distributed U.S. cities: Los Angeles, San Francisco, Denver, Detroit, Boston, and Baltimore. From the entire sample set of beef and chicken, only 12 servings of beef had 13C < 21‰; for these animals only was a food source other than corn possible. We observed remarkably invariant values of 15N in both beef and chicken, reflecting uniform confinement and exposure to heavily fertilized feed for all animals. The 13C value of fries differed significantly among restaurants indicating that the chains used different protocols for deep-frying: Wendy’s clearly used only corn oil, whereas McDonald’s and Burger King favored other vegetable oils; this differed from ingredient reports. Our results highlighted the overwhelming importance of corn agriculture within virtually every aspect of fast food manufacture. (Hope Jahren and Rebecca A. Kraft, Carbon and nitrogen stable isotopes in fast food: Signatures of corn and confinement, PNAS 2008, November 10, 2008, doi: 10.1073/pnas.0809870105)

The method here is to examine the ratios of different isotopes of carbon and nitrogen in the meat and potato samples. Both naturally found carbon and nitrogen are mixtures of chemically identical atoms with different atomic weights (their nuclei have the same number of protons, and hence the same number of orbiting electrons, which determine the chemistry, but have different numbers of neutrons; for carbon it is 6, 7 or 8 giving atomic weights of 12, 13 and 14). Some isotopes, like carbon with an atomic weight of 14 are unstable, but most isotopes are stable (carbon-12 and carbon-13 being examples of stable isotopes. By determining the relative percentages of stable isotopes we can often get information on the source of the carbon or nitrogen and that was the method used here. The percentages of carbon-13 in the samples indicated if the feed was corn (corn has a characteristic stale isotope signature) and the nitrogen-15 samples gave evidence for high intensity fertilizer use on the feed crops.

Using published data, the authors note that if we eat just one hamburger, one chicken sandwich and one small order of fries we will be getting 50% of our recommended calories for the day, 80% of our carbs and 75% of our protein (90% for women). We would also be getting a full day’s worth of saturated fat. And all for just about $3.

This is a pretty remarkable nutritional bargain, but of course there are hidden costs (beyond the heart attack on a plate aspect). Corn as a feedstock is not only wasteful but highly subsidized. Our cheap meal is being paid for in other ways (taxes). This high tech effort to find out the raw inputs to the hamburger-chicken-fries factory was needed because the industry has successfully resisted any requirement for disclosure as they have in Europe:

Fastfood corporations do not raise livestock, but instead buy it from other companies. Birth, growth, and slaughter are distinct events occurring at different facilities, often under different companies. Each fast food chain employs distributor companies: These suppliers organize and broker the production and transport of meat to the site of food fabrication and sale. In this way, distributors act as a barrier to consumer information†; suppliers relevant to this study provide little information beyond their use of ”local farms” that feed ”mixed grains.” The distributor for McDonald’s is Martin-Brower, L.L.C.; Burger King and Wendy’s employ the same distributor, Maines Paper and Food Service, Inc. These differences probably drive the significant differences in 13C content of beef among chains, and between West Coast and other restaurants. In contrast, all chicken is distributed to each chain by the same company, Tyson Foods, Inc.; the extreme homogeneity seen in chicken 13C content across all aspects of the study, speaks to the virtually identical process of chicken production for the majority of American fast food.

The authors of this remarkable study bought 160 items at Wendy’s restaurants in various parts of the US. As they report, not a single item was traceable to a non-corn source. This was essentially true for the chicken and beef in McDonald’s and Burger King, but those chains often used non-corn oils for their french fries. They also note that the high fructose corn syrup used as beverage sweetener in these restaurants was not considered.

We not only know the names of the chains, but in files found in the Supporting Information we you can find a full list of the addresses in each city of the restaurants from which the samples were purchased (strangely, the ones listed as Boston come from restaurants in Worcester, MA). This is an admirable (and unusual) degree of disclosure for a scientific paper of consumer products. Kudos to the authors (who are based at the Department of Geology and Geophysics at the University of Hawaii).

NB: Just learned that Ed at Not Exactly Rocket Science has also posted on this. Check it out.