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Harvard Study: Quality of U.S. Diet Remains Poor

Authors find widening disparities in diet quality between rich and poor

Dietary quality in the U.S. has improved steadily in recent years — spurred in large part by the reduced intake of trans fats — but overall dietary quality remains poor, and disparities continue to widen among socioeconomic and racial/ethnic groups, according to a new study from the Harvard School of Public Health (HSPH).

“The study provides the most direct evidence to date that the extensive efforts by many groups and individuals to improve U.S. dietary quality are having some payoff, but it also indicates that these efforts need to be expanded,” said lead author Dong Wang, a doctoral student in the Department of Nutrition at HSPH.

The study was published online September 1 in JAMA Internal Medicine.

Given changes in the economy, in policies related to nutrition, and in food processing since the turn of the century, the researchers decided to investigate recent trends in dietary quality in the U.S. They also investigated trends within different socioeconomic subgroups because differences in diet can contribute to variations in the burden of chronic diseases, such as heart disease, diabetes, and cancer. Evaluating these trends is important to help guide public health policy and to improve strategies to prevent nutrition-related chronic diseases, Wang said.

The data came from a nationally representative sample of 29,124 adults 20 to 85 years of age inthe U.S. 1999–2010 National Health and Nutrition Examination Surveys. The authors evaluated dietary quality over time using the Alternate Healthy Eating Index 2010 (AHEI-2010), which rates dietary quality on a score of 0 to 110 (with higher scores indicating healthier diets), and which predicts major chronic diseases. The investigators also used another dietary quality index, the Healthy Eating Index 2010.

The average AHEI-2010 score increased from 39.9 in 1999–2000 to 46.8 in 2009–2010, and the researchers found that more than half of the gain came from the reduced consumption of trans fats. The overall improvement in dietary quality reflected changes in consumers’ food choices and in the makeup of processed foods, and was likely the result of public policy efforts and nutrition education, the authors said.

They noted that the significant reduction in the consumption of trans fats suggested that collective actions, such as legislation and taxation, are more effective in supporting people’s healthy choices than actions that depend solely on individual, voluntary behavior change.

Other changes in eating habits also played a significant role in boosting dietary quality. People are eating more whole fruit, whole grains, nuts, legumes, and polyunsaturated fats, and they’re drinking fewer sugar-sweetened beverages, the study found. On the other hand, people did not eat more vegetables or less red and/or processed meat. Moreover, their salt intake increased — which the researchers found “disconcerting.”

The results showed that people with a higher socioeconomic status had healthier diets than did people with a lower socioeconomic status, with the gap increasing from 1999 to 2010.

These income-related differences in diet quality are likely associated with price (healthy foods generally cost more) and access (low-income people may have limited access to stores that sell healthy foods), the authors wrote. They also noted that education played a role: dietary quality was lowest and improved more slowly among those who had had 12 years or less of school.

Among racial and ethnic groups, Mexican-Americans had the best dietary quality, whereas non-Hispanic blacks had the poorest. The lower diet quality among non-Hispanic blacks was explained by lower income and education. The authors speculated that Mexican-Americans’ better-quality diets may be due to dietary traditions or culture. Among all groups, women generally had better-quality diets than men.

Source: EurekAlert; September 1, 2014.

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