Dietary Patterns and Health: Insights From NESR Systematic Reviews to Inform the Dietary Guidelines for Americans.

This perspective article shares unique insights from the extensive experience of the US Department of Agriculture Nutrition Evidence Systematic Review branch in conducting systematic reviews on dietary patterns and health outcomes to inform the Dietary Guidelines for Americans. Methodological approaches for reviewing dietary patterns research are described, including approaches to operationalizing definitions and analyzing labeled dietary patterns. The review also describes techniques for synthesizing dietary patterns research across life stages in systematic reviews that inform food-based, federal dietary guidance. Current research activities and recommendations for how to improve or address gaps in dietary patterns research in the future are also discussed.

Evaluation of Dietary Patterns and All-Cause Mortality: A Systematic Review.

Importance: The 2020 Dietary Guidelines Advisory Committee conducted a systematic review of existing research on diet and health to inform the current Dietary Guidelines for Americans. The committee answered this public health question: what is the association between dietary patterns consumed and all-cause mortality (ACM)? Objective: To ascertain the association between dietary patterns consumed and ACM. Evidence Review: Guided by an analytical framework and predefined inclusion and exclusion criteria developed by the committee, the US Department of Agriculture's Nutrition Evidence Systematic Review (NESR) team searched PubMed, the Cochrane Central Register of Controlled Trials, and Embase and dual-screened the results to identify articles that were published between January 1, 2000, and October 4, 2019. These studies evaluated dietary patterns and ACM in participants aged 2 years and older. The NESR team extracted data from and assessed risk of bias in included studies. Committee members synthesized the evidence, developed conclusion statements, and graded the strength of the evidence supporting the conclusion statements. Findings: A total of 1 randomized clinical trial and 152 observational studies were included in the review. Studies enrolled adults and older adults (aged 17-84 years at baseline) from 28 countries with high or very high Human Development Index; 53 studies originated from the US. Most studies were well designed, used rigorous methods, and had low or moderate risks of bias. Precision, directness, and generalizability were demonstrated across the body of evidence. Results across studies were highly consistent. Evidence suggested that dietary patterns in adults and older adults that involved higher consumption of vegetables, fruits, legumes, nuts, whole grains, unsaturated vegetable oils, fish, and lean meat or poultry (when meat was included) were associated with a decreased risk of ACM. These healthy patterns were also relatively low in red and processed meat, high-fat dairy, and refined carbohydrates or sweets. Some of these dietary patterns also included intake of alcoholic beverages in moderation. Results based on additional analyses with confounding factors generally confirmed the robustness of main findings. Conclusions and Relevance: In this systematic review, consuming a nutrient-dense dietary pattern was associated with reduced risk of death from all causes.

Caregiver feeding practices and child weight outcomes: a systematic review.

BACKGROUND: As part of the USDA-Department of Health and Human Services Pregnancy and Birth to 24 Months Project, we conducted systematic reviews (SRs) on topics important for health and nutrition of young children. OBJECTIVES: The purpose of the present SR was to examine the relation between caregiver feeding practices in children from birth to 24 mo and child weight gain, size, and body composition. METHODS: A search of articles published from January 1980 to January 2017 in 4 databases identified 8739 references. Nutrition Evidence Systematic Review (NESR) analysts used the Nutrition Evidence Library Risk of Bias Assessment Tool to assess potential bias in the studies, and a Technical Expert Collaborative graded the body of evidence using the NESR grading rubric. RESULTS: Twenty-seven articles were included in this review (8 controlled trials, 19 longitudinal cohort studies). Moderate evidence from randomized controlled trials suggests that providing responsive feeding guidance to teach mothers to recognize and respond appropriately to children's hunger and satiety cues can lead to "normal" weight gain and/or "normal" weight status in children aged ≤2 y compared with children whose mothers did not receive responsive feeding guidance. Moderate evidence from longitudinal cohort studies indicates an association between maternal feeding practices and the child's weight status and/or weight gain, but the direction of effect has not been adequately studied. Restrictive feeding practices are associated with increased weight gain and higher weight status, and pressuring feeding practices are associated with decreased weight gain and lower weight status. Evidence suggests that a mother's feeding practices are related to concerns about her child's body weight. CONCLUSIONS: This review highlights the importance of the interaction between caregivers and infants and toddlers related to child feeding practices on children's weight outcomes. Research is needed on more diverse populations with consistent methodological app-roaches and objective measures.

Influence of maternal diet on flavor transfer to amniotic fluid and breast milk and children's responses: a systematic review.

BACKGROUND: Maternal diet during pregnancy and lactation may provide the earliest opportunity to positively influence child food acceptance. OBJECTIVE: Systematic reviews were completed to examine the relation among maternal diet during pregnancy and lactation, amniotic fluid flavor, breast-milk flavor, and children's food acceptability and overall dietary intake. DESIGN: A literature search was conducted in 10 databases (e.g., PubMed, Embase, Cochrane, and CINAHL) to identify articles published from January 1980 to June 2017. Data from each included study were extracted, risk of bias assessed, evidence synthesized qualitatively, conclusion statements developed, and strength of the evidence graded. RESULTS: Eleven and 15 articles met a priori criteria for inclusion to answer questions related to maternal diet during pregnancy and lactation, respectively. CONCLUSIONS: Limited but consistent evidence indicates that flavors (alcohol, anise, carrot, garlic) originating from the maternal diet during pregnancy can transfer to and flavor amniotic fluid, and fetal flavor exposure increases acceptance of similarly flavored foods when re-exposed during infancy and potentially childhood. Moderate evidence indicates that flavors originating from the maternal diet during lactation (alcohol, anise/caraway, carrot, eucalyptus, garlic, mint) transmit to and flavor breast milk in a time-dependent manner. Moderate evidence indicates that infants can detect diet-transmitted flavors in breast milk within hours of a single maternal ingestion (alcohol, garlic, vanilla, carrot), within days after repeated maternal ingestion (garlic, carrot juice), and within 1-4 mo postpartum after repeated maternal ingestion (variety of vegetables including carrot) during lactation. Findings may not generalize to all foods and beverages. Conclusions cannot be drawn to describe the relationship between mothers' diet during either pregnancy or lactation and children's overall dietary intake.

Repeated exposure to food and food acceptability in infants and toddlers: a systematic review.

BACKGROUND: Repeated exposure has been found to be an effective strategy to increase acceptability of foods in older children and adults, but little is known about its effectiveness in the birth to 24-mo population. OBJECTIVES: This systematic review was conducted to examine the effects of repeated exposure to a single or multiple foods on acceptance of those or other foods among infants and toddlers. METHODS: A search was conducted for peer-reviewed articles related to food acceptability, flavor, taste, and infants and toddlers in 12 databases (e.g., PubMed, Embase, Cochrane, and CINAHL) with a date range of January 1980 to July 2017. The Nutrition Evidence Library (NEL) Bias Assessment Tool was used to assess potential bias in the included studies, and the NESR grading rubric was used to grade evidence supporting the conclusion statement. RESULTS: From the 10,844 references obtained, 21 studies (19 controlled trials and 2 longitudinal cohort studies) published from 1980 to 2015 were included in this review. Moderate evidence indicates that tasting a single vegetable or fruit or multiple vegetable(s) or fruit(s) 1 food per day for 8-10 or more days is likely to increase acceptability of an exposed food (indicated by an increase in intake or faster rate of feeding after comparison with before the exposure period) in infants and toddlers 4-24 mo old. The effect of repeated exposure on acceptability is likely to generalize to other foods within the same food category but not foods from a different food category. Findings are based on the effects of repeated exposure to mostly vegetables with some findings on repeated exposure to fruits. CONCLUSION: This review advances the understanding of early food experiences and the development of food acceptability. Additional research is needed using diverse foods and textures with a focus on the transition to table foods.

Systematic review methods for the Pregnancy and Birth to 24 Months Project.

The USDA's Nutrition Evidence Systematic Review (NESR) team specializes in conducting systematic reviews (SRs) to inform federal nutrition policy and programs. The NESR's dedicated staff collaborate with leading scientists to answer important food- and nutrition-related public health questions by objectively reviewing, evaluating, and synthesizing research using state-of-the-art methodology. NESR uses a rigorous, protocol-driven methodology that is designed to minimize bias; to ensure availability of SRs that are relevant, timely, and high quality; and to ensure transparency and reproducibility of findings. This article describes the methods used by NESR to conduct a series of SRs on diet and health in infants, toddlers, and women who are pregnant as part of the Pregnancy and Birth to 24 Months Project.