Dietary risk factors are among the key contributors to mortality and
morbidity in the United States and globally, and there is increasing
emphasis on understanding the influence of total diet quality and
overall dietary patterns rather than single aspects of what we eat and
drink. In order to evaluate the quality of what people eat and drink,
researchers often rely on recommendations such as the Dietary Guidelines
for Americans (DGA). In the latest issue of the
Journal of the Academy of Nutrition and Dietetics,
leading nutrition experts describe and evaluate the latest version of
the Healthy Eating Index (HEI), which has been issued to correspond to
the 2015-2020 Dietary Guidelines for Americans.
The DGA are updated every five years, leading to changes in emphasis
and quantification, as the evidence on healthy eating evolves over
time. Likewise, a new HEI is issued to correspond to each new edition of
the DGA and to reflect these changes. The HEI is a measure of diet
quality, independent of quantity, that can be used at various levels of
the food stream, including the national food supply, the community food
environment (e.g., foods available at a school or a fast food menu), and
food intakes among the population.
The HEI score can be used to evaluate how healthy the American diet
is in relation to federal dietary guidance. It has been applied by
researchers to describe diet quality among the US population, as well as
population subgroups such as Mexican Americans, children, and cancer
survivors. It has also been used to evaluate the quality of food
offerings across the food stream, including the US food supply,
restaurant menus, grocery store circulars, and Federal food distribution
programs.
"Tracking quality at these different levels is critical since we are
increasingly recognizing the power of the food environment on eating
behavior. That is, individuals cannot be expected to make healthy
choices if those options are not readily available in the home, at work,
at school, and in the community," comments Jill Reedy, PhD, MPH, RD,
Program Director at the Risk Factor Assessment Branch, Epidemiology and
Genomics Research Program, Division of Cancer Control and Population
Sciences, National Cancer Institute, National Institutes of Health,
Bethesda, MD, USA, and co-author of the papers in this issue.
The latest HEI was developed through a collaboration between
researchers at the National Cancer Institute (NCI) and the United States
Department of Agriculture's (USDA) Center for Nutrition Policy and
Promotion (CNPP). A trio of papers in this special issue introduce the
new HEI and describe differences compared to the 2010 and 2005 editions,
evaluate the properties of the HEI-2015 for assessing dietary quality,
and discuss its applications.
Update
The first
paper
outlines the steps taken to update the most recent version of the HEI
and prepare an HEI-2015 scoring system to reflect compliance with the
2015-2020 DGA food and nutrient recommendations. "The Dietary Guidelines
for Americans evolve incrementally over time based on scientific
evidence, and updates to the HEI are designed to capture that
evolution," explains Susan M. Krebs-Smith, PhD, MPH, Risk Factor
Assessment Branch, Epidemiology and Genomics Research Program, Division
of Cancer Control and Population Sciences, National Cancer Institute,
National Institutes of Health, Bethesda MD, USA.
The 2015 edition has 13 components, each reflecting an important
aspect of diet quality as per the DGA. Dr. Krebs-Smith and colleagues
describe each of the HEI-2015's constituent food and nutrient
categories, as well as its 100-point scoring system, including referent
standards for each component of the total score. Since the 2005 version,
the HEI has been based on densities (e.g., amounts per 1000 kcal),
rather than absolute amounts, and relies on a common set of standards
that are applicable across individuals and settings. Notable differences
compared to the previous edition are that saturated fat and added
sugars are each separately tracked, and excessive alcohol contribution
to energy is not captured separately. This new version also incorporates
modifications to the scoring procedures for legumes.
Evaluation
In the second
paper,
Jill Reedy, PhD, MPH, RD, and colleagues report on testing of the
index's validity and reliability. Known high-quality sample menus from a
variety of organizations such as the National Heart, Lung, and Blood
Institute (Dietary Approaches to Stop Hypertension [DASH] diet), US
Department of Agriculture (USDA), Harvard Medical School (Healthy Eating
Guide), and the American Heart Association (AHA) (No-Fad Diet) were
scored using the HEI standards. These menus all achieved high scores,
ranging from 88 to 100 points.
At the next level of testing, data from the Centers for Disease
Control and Prevention's National Health and Nutrition Examination
Survey (NHANES) were used to compare HEI-2015 scores across population
subgroups to examine if meaningful differences could be detected.
Average HEI-2015 scores and ranges demonstrated reasonable variation
across the subgroups examined, including groups differentiated by age,
gender, and smoking status. Results suggested that the index reflects
the many dimensions of dietary guidance. As a final assessment, datasets
from the NIH-AARP Diet and Health Study were examined and showed that
individuals in the highest quintiles of HEI-2015 scores had a 13-23
percent decreased risk of all-cause, cancer, and cardiovascular disease
mortality.
"These analyses demonstrated evidence supportive of validity and
reliability for the HEI-2015, as has been shown in earlier work with the
HEI-2005 and HEI-2010," notes Dr. Reedy. "However, limitations in the
HEI as well as those inherent to dietary intake data more broadly should
be considered in any application of the index."
Applications
The third
paper
examines potential applications of the HEI-2015 in surveillance,
epidemiology, and community intervention research. Lead investigator
Sharon I. Kirkpatrick, PhD, MHSc, RD, Associate Professor, School of
Public Health and Health Systems, University of Waterloo, Waterloo, ON,
Canada, and colleagues outline approaches to calculating scores and
review their suitability for research questions related to monitoring
eating patterns, understanding associations between eating patterns and
health/disease, and evaluating dietary interventions.
The focus of this paper is on the use of the HEI for cases in which
dietary intake data are available for characterizing diet quality for
groups of individuals sampled from the population. Further development
of methods for calculating the HEI for individuals will help advance our
knowledge on diet quality. "The use of the most appropriate approach to
calculating HEI scores for a given purpose can help build a stronger
literature on the influence of dietary quality on health and disease
risk, helping to inform future policies and programs to support health,"
comments Dr. Kirkpatrick.
In an accompanying
editorial,
Barbara Millen, DrPH, MPH, RD, FADA, Millennium Prevention, Inc., and
Boston Nutrition Foundation, Inc., Westwood, MA, USA, and Chairman of
the 2015 Dietary Guidelines Advisory Committee, points out the growing
use of web and mobile platforms and apps in clinical and community
settings for purposes such as diet and exercise behavior monitoring. She
forecasts a bright future for integrating new methods of nutritional
risk assessment, such as the HEI-2015, with advanced analytics and
innovative web and mobile technologies.
According to Dr. Millen, "The evidence base is stronger than ever
before linking the 'total diet' - its dietary patterns, nutrient
density, and overall quality - to health promotion and disease
prevention across the human life span. The work of these investigators
will hopefully inspire other researchers and nutrition professionals to
utilize the HEI-2015 broadly and establish other evidence-based
innovations that fully embrace the 2015-2020 DGA's five cornerstone
guidelines, and advance research and practice in clinical, public health
and consumer settings."