Though people in the U.S. have done well to improve their diets by reducing trans fat intake, overall dietary quality remains poor and disparities continue to widen among socioeconomic and racial/ethnic groups, according to a new study from Harvard School of Public Health.
“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 Dong Wang, lead author of the study and a doctoral student in the department of nutrition at HSPH. The study appeared online, September 1, in JAMA Internal Medicine (doi:10.1001/jamaint ernmed.2014.3422).
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., said an HSPH press release. The researchers also investigated trends within different socioeconomic sub-groups because differences in diet can contribute to variation in the burden of chronic diseases such as heart disease, diabetes and cancer. Evaluating these trends is important in helping to guide public health policy and improve strategies to prevent nutrition-related chronic diseases, Wang said.
Data came from a nationally representative sample of 29,124 adults aged 20–85 from the U.S. 1999–2010 National Health and Nutrition Examination Surveys. The scientists evaluated dietary quality over time using the Alternate Healthy Eating Index 2010 (AHEI-2010), which rates dietary quality on a score of 0–110 (with higher scores indicating healthier diets), and which strongly predicts major chronic disease. They also used another dietary quality index, the Healthy Eating Index 2010 (HEI).
Areas of the U.S. diet that are improving:
- The average AHEI–2010 score increased
from 39.9 in 1999–2000 to 46.8 in 2009– 2010; researchers attributed more than half of the gain to reduced consumption of trans fats.
- Americans are eating more whole fruit, whole grains, nuts, legumes and polyunsaturated fats.
- We are drinking fewer sugar-sweetened beverages.
Areas of the U.S. diet that need improvement:
- We need to eat more vegetables.
- We need to eat less red and/or processed
- We have increased our salt intake, which
researchers found “disconcerting.”
- The gap in diet quality between rich and
poor is growing. 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), according to the authors. They also noted that education plays a role: Dietary quality was lowest and improved more slowly among those who had had 12 or fewer years of schooling.
“The overall improvement in diet quality is encouraging, but the widening gap related to income and education presents a serious challenge to our society as a whole,” said Walter Willett, MD, DrPH, professor of epidemiology and nutrition, chair of the department of nutrition at HSPH and senior author of the study.