Why people eat the foods they do

People purchase foods based on their income level, their belief in a food's health benefit and cost. However, ethnicity and gender also impact people's food choices, according to researchers at the Johns Hopkins Bloomberg School of Public Health.

The study, published in the March 7, 2007, advance online publication of the European Journal of Clinical Nutrition, reports that food choice is also influenced by environmental factors, such as reliance on fast food, food advertising and food pricing, and on individual factors, such as taste, palatability, convenience and health benefits.

The study sample included 4,356 U.S. adults aged 20-65 years from two nationally-representative cross-sectional surveys conducted by the U.S. Department of Agriculture (USDA)—the Continuing Survey of Food Intakes by Individuals and the Diet and Health Knowledge Survey. The Johns Hopkins Center for Human Nutrition researchers examined diet quality indicators, such as the amount of energy, energy density, total fat and saturated fat in foods consumed by study participants. They also considered the quantity of fruits and vegetables, fiber, calcium and dairy products consumed and the overall quality of people's diet, which was assessed using two indices, including one recommended by the USDA. The key findings are as follows:

• There are considerable ethnic and gender differences in the association between socio-economic status, perceived barrier of food price, perceived benefit of diet quality and dietary intake.
• Income constraints on individuals and families can lead to a poorer quality diet. When buying food, African-Americans with lower incomes saw food price as more important than Whites with the same income level did.
• Caucasians of lower socio-economic status ate more fat and saturated fat. African-Americans showed no association between income level and fat intake.
• Among all study participants, and independent of income, the perceived barrier of food price appears to increase sodium intake while reducing fiber intake.
• Perceived benefit of diet quality was directly related to better nutritional behavior, including consuming foods less in saturated fat and eating more fiber, fruits and vegetables. Compared to men, women were more concerned about meeting food guidelines in order to improve their health.
• Women had lower energy, energy density, total fat, saturated fat, cholesterol and sodium intake than men. Yet, men had higher intake of fruits and vegetables, fiber, calcium and dairy products, particularly because they consumed more food.

"Low socio-economic status may cause a significant food-cost barrier, which in turn, reduces the quality of an individual's diet. Considering the growing obesity crisis, it is important to make healthy foods accessible to poor segments of the population and to empower them to eat a healthy diet by lowering the price of healthy foods and enhancing tailored nutrition education," said Youfa Wang, MD, PhD, co-author of the study and an assistant professor in the Bloomberg School of Public Health's Department of International Health. "Programs that promote positive attitudes towards the benefits of healthy diets can improve diet quality for both genders and all ethnicities."

"People's diets are affected by many factors. We examined some of those factors. Therefore, a large proportion of the association between income level and dietary intake could not be explained by the perceived barrier of food price or the perceived benefit of diet quality," added May A. Beydoun, coauthor of the study and a postdoctoral fellow in the Bloomberg School of Public Health's Department of International Health.

The study authors recommend additional studies aimed at uncovering the complex relationships between socio-economic status, nutritional knowledge, attitudes and perceptions and dietary behavior and food choices.

May A. Beydoun and Youfa Wang, both of the Johns Hopkins Bloomberg School of Public Health, co-authored the study.

"How do socio-economic status, perceived economic barriers and nutritional benefits affect quality of dietary intake among US adults" was supported by grants from the Johns Hopkins Bloomberg School of Public Health, the U.S. Department of Agriculture, the National Institute of Diabetes & Digestive & Kidney Diseases and the Johns Hopkins Center for a Livable Future.