On page 17 of The Omnivore's Dilemma, Pollan says that a consumer has "to be a fairly determined ecological detective" to figure out where processed food comes from, while it is easier to determine the origin of less or non-processed food. When he traced the long food chains of processed food (meaning determining where they came from), he found that many of them go back to the American Corn Belt and a single species called the Zea mays, or corn. For example, most cows, chickens, pigs, and even fish such as salmon feed on corn. In addition, processed food such as chicken nuggets are made up of chicken that has been fed on corn combined with corn (see page 18). The chicken nugget is fried in corn oil and mixed with corn flour. The additives, preservatives, and colorings also come from corn. Since the 1980s, most sodas and fruit drinks have been sweetened with high-fructose corn syrup (HFCS). As Pollan says on page 95, processing food can add months or even years to its shelf life, increasing the profit for the producer and giving the food a global market. 

The hormones and antibiotics in these foods contaminate the environment. On page 81, Pollan explains that since we share the same ecosystem as the animals, what they eat affects us. As corn makes cows less healthy, so it also makes us less healthy. Animals are fed so many antibiotics that these antibiotics, either in food or in the soil that is used to grow other food, can make humans more resistant to new strains of bacteria. In addition, cattle raised in feedlots contain a strain of E. coli that can be toxic to humans. Everything added to food or used to feed animals winds up in the ecosystem and affects the environment and our health.