How The Availability Of Food Affects Diets

The Industrial Revolution that took root in the nineteenth century transformed farming in the United States in the twentieth century. Increased mechanization in the fields led to more efficient fertilization, better crop rotation techniques and rapid harvests that minimized food loss. High-yield crops and selective plant breeding followed these gains and exploded production further in the 1960s and beyond. This abundance created a growth in the food supply that surpassed population increases, against all expectations. The increased availability is not necessarily correlated to an increase in diet quality, however, and sharp divisions remain between social classes.

Food Availability

The Economic Research Service, a division of the U.S. Department of Agriculture, compiles and analyzes food availability data as a proxy for food consumption. By measuring food production and the availability of that output per capita, the ERS is able to make assumptions about consumption patterns and changes in macronutrient proportions in the average diet as well as target the areas of overconcentration and underconcentration of quality food sources for further study.

Increased Consumption

Since 1970, total calorie consumption per capita in the United States has increased more than 20 percent to 2,704 per person in 2007 from 2,172 per person in 1970. The 533-calorie increase is due almost exclusively to an increase in the consumption of fats and oils and refined grains, according to the USDA. More than 400 calories of the increase are due to these two nutrient groups while fruits and vegetables accounted for just 28 calories of the increase.

Diet Quality

The United States has the least expensive food supply in the world, leading to widespread and equitable food availability across the socioeconomic spectrum, but the cost of higher quality, nutrient-dense foods compared with energy-dense, nutrient-poor sources leads to dramatic differences in diet quality among social classes. The data demonstrating a correlation between socioeconomic status and diet quality indicate that higher-income Americans consume more lean meats, fresh vegetables and low-fat dairy while groups with lower socioeconomic status rely more on foods with added fats and refined grains, according to a study by Nicole Darmon and Adam Drewnowski published in the "American Journal of Clinical Nutrition," May 2008.

Retail Availability

According to the analysis by Darmon and Drewnowski, affluent population subgroups are thinner, healthier and report a higher-quality diet than those groups in the lower socioeconomic categories. Part of the influence on diet quality has to do with retail food availability, or the presence of high quality foods within a given retail outlet and the number of quality outlets in a neighborhood or region.

Social Classes

Lower-income populations are more exposed to fast foods and lower quality dietary choices than are the higher-income subgroups, leading to increased incidence of obesity, heart disease and diabetes among the poor, according to the Darmon and Drewnowski study. Minority groups are also disproportionately exposed to low-quality food sources. Sixty-two percent of minority respondents to a study by Latetia V. Moore, et al, published in the "American Journal of Epidemiology," July 2009, reported that they typically ate fast food at least once per week within one mile of the home. White, affluent respondents were less likely to consume low-quality diet choices near the home than all other groups surveyed.