Newswise, November 2, 2015– Diet diversity, as defined by less
similarity among the foods people eat, may be linked to lower diet quality and
worse metabolic health, according to researchers at The University of Texas
Health Science Center at Houston (UTHealth) and the Friedman School of
Nutrition Science and Policy at Tufts University. The study was published today
in PLOS ONE.
“‘Eat everything in moderation’ has been a long-standing
dietary recommendation, but without much empiric supporting evidence in
populations.
“We wanted to characterize new metrics of diet diversity and
evaluate their association with metabolic health,” said Marcia C. de Oliveira
Otto, Ph.D., first author and assistant professor in the Department of
Epidemiology, Human Genetics and Environmental Sciences at UTHealth School of
Public Health.
Using data from 6,814 participants in the Multi-Ethnic Study
of Atherosclerosis, a study of whites, blacks, Hispanic-Americans and
Chinese-Americans in the United States, the authors measured diet diversity
through different measures.
These included the total count (number of different foods
eaten in a week), evenness (the distribution of calories across different foods
consumed), and dissimilarity (the differences in food attributes relevant to
metabolic health, such as fiber, sodium or trans-fat content).
Researchers evaluated how diet diversity was associated with
change in waist circumference five years after the beginning of the study and
with onset of Type 2 diabetes 10 years later. Waist circumference is an
important indicator of central fat and metabolic health.
When evaluating both food count and evenness, no associations
were seen with either increase in waist circumference or incidence of diabetes.
In other words, more diversity in the diet was not linked to better outcomes.
Participants who had the greatest food dissimilarity actually
experienced more central weight gain, with a 120 percent greater increase in
waist circumference than participants with the lowest food dissimilarity.
To compare with the results seen for diet diversity, the
researchers also examined how diet quality relates to metabolic health. Diet
quality was measured using established scores such as the Dietary Approaches to
Stop Hypertension (DASH) score and the Alternative Healthy Eating Index (AHEI)
score. At five years, diet quality was not associated with change in waist
circumference.
At ten years, higher diet quality was associated with about a
25 percent lower risk of developing Type 2 diabetes.
“An unexpected finding was that participants with greater
diversity in their diets, as measured by dissimilarity, actually had worse diet
quality. They were eating less healthy foods, such as fruits and vegetables,
and more unhealthy foods, such as processed meats, desserts and soda,” said
Otto.
“This may help explain the relationship between greater food
dissimilarity and increased waist circumference.”
Dietary diversity as measured by food count and evenness was
also associated with higher intakes of both healthy and unhealthy foods.
“Americans with the healthiest diets actually eat a relatively
small range of healthy foods,” said Dariush Mozaffarian, M.D., Dr.P.H., senior
author and dean of the Friedman School of Nutrition Science and Policy at Tufts
University in Boston.
“These results suggest that in modern diets, eating ‘everything
in moderation’ is actually worse than eating a smaller number of healthy
foods.”
Nikhil S. Padhye, Ph.D., from UTHeath School of Nursing, was a
coauthor on the study. Funding came from a research supplement grant awarded to
Otto by the National Heart, Lung and Blood Institute of the National Institutes
of Health, as part of a larger research grant number R01HL085710, whose
principal investigator is the senior author Mozaffarian.
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