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Advancing Human Nutrition Research

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The ARS human nutrition research program enhances the quality of the American diet and improves health through research. Obesity is estimated to cost $190 billion annually, and as its prevalence has increased over recent decades, ARS scientists have researched innovative ways of reversing that trend. Since agriculture primarily produces food for human consumption, integrating human nutrition research into ARS is critical for solving the biggest problems facing producers and consumers. The following accomplishments highlight ARS advances human nutrition research in FY 2020.

Dietary carbohydrate intake contributes to reduced stress. Mental stress is linked to risk of chronic diseases. In an 8-week randomized controlled trial that compared effects of a healthy Dietary Guidelines for Americans (DGA)-based diet against the less healthy typical American diet, ARS scientists in Davis, CA, found that the DGA diet, with a higher amount of dietary carbohydrate, resulted in reduced concentrations of a key stress response hormone, cortisol, and dampened stress-induced cortisol reactions. These novel findings provide new evidence suggesting that in the context of a healthy diet, carbohydrate consumption may provide some protection from stress-related disease risk. Furthermore, this apparent stress and cortisol dampening effect could reduce stress-related eating by some individuals and improve their ability to sustain a healthier diet based on the DGA.

Breastfeeding alters gut bacteria, impacts immune health in infants. Early nutrition can significantly affect intestinal colonization by normal bacteria and modulate host health through a series of bacterial metabolites that interact with cells of the body. ARS-supported scientists in Little Rock, AR, analyzed fecal samples from infants in an effort to describe the bacteria and their metabolites over the course of the first year of life in babies who were exclusively fed breastmilk or formula. Breastfeeding resulted in increased abundance of bacteria that produce short-chain fatty acids and metabolites that serve as signals in development of the gut and other organs. In addition, bacterial metabolites such as kynurenic acid, which helps optimize immune responses, including inhibiting allergy, were higher in breastfed infants. These results provide new information about how breastfeeding promotes intestinal and immune health in infants and adds to the scientific basis for the recommendation by the Centers for Disease Control and Prevention that infants should be breastfed.

First ever expert advice to parents and caregivers on healthy eating behaviors in young children. Researchers know that to prevent childhood obesity, how children eat may be as important as what they eat. In addition, we know that the first 5 years of life are a critical period for helping children learn how to regulate their food intake to match their energy needs. ARS-supported researchers in Houston, TX, led a partnership with other scientific experts and the American Heart Association to release their first ever scientific statement giving advice on how to foster healthy eating behaviors in children under 5 years of age. This guidance will broadly reach parents and caregivers across the country and provide strategies for healthy eating behaviors with the goal of reducing childhood obesity.

Obesity dampens immune responses in young women to levels similar to those of elderly. Both obesity and aging are associated with muted immune and inflammatory responses. Limited knowledge, however, exists on differences in the immune system between young and older adults with obesity. ARS-supported scientists in Boston, MA, conducted a study to compare circulating indicators of immunity in young and older women with obesity. Twenty-three young (age 23–43) and 21 older (age 60–83) women with obesity participated. Older women with obesity had significantly fewer circulating immune cells of four specific types than young women. With few exceptions, there was no significant difference in inflammation markers or stimulated lymphocyte proliferation and cytokine production by peripheral blood mononuclear cells between young and older participants. These findings contrast with those previously reported in young and older subjects with healthy weight and call for further investigation into the impact of obesity on premature aging of the immune system.