A Proposed Framework for Identifying Nutrients and Food Components of Public Health Relevance in the Dietary Guidelines for Americans.

BACKGROUND: Identification of nutrients of public health concern has been a hallmark of the Dietary Guidelines for Americans (DGA); however, a formal systematic process for identifying them has not been published. OBJECTIVES: We aimed to propose a framework for identifying "nutrients or food components" (NFCs) of public health relevance to inform the DGA. METHODS: The proposed framework consists of 1) defining terminology; 2) establishing quantitative thresholds to identify NFCs; and 3) examining national data. The proposed framework utilizes available data from 3 key data sources or "prongs": 1) dietary intakes; 2) biological endpoints; and 3) clinical health consequences such as prevalence of health conditions, directly or indirectly through validated surrogate markers. RESULTS: In identifying potential NFCs of public health concern, the 2020 DGA Committee developed a decision-tree framework with suggestions for combining the 3 prongs. The identified NFCs of public health concern for Americans ≥1 y old included fiber, calcium (≥2 y old), vitamin D, and potassium for low intakes and sodium, added sugars, and saturated fats (≥2 y old) for high intakes that were associated with adverse health consequences. Iron was identified among infants ages 6-12 mo fed human milk. For reproductive-aged and pregnant females, iron (all trimesters) and folate (first trimester) were identified for low intake, based on dietary and biomarker data (iron) or the severity of the consequence (folic acid and neural tube defects). Among pregnant women, low iodine was of potential public health concern based on biomarker data. Other NFCs that were underconsumed, overconsumed, and pose special challenges were identified across the life course. CONCLUSIONS: The proposed decision-tree framework was intended to streamline and add transparency to the work of this and future Dietary Guidelines Advisory Committees to identify NFCs that need to be encouraged or discouraged in order to help reduce risk of chronic disease and promote health and energy balance in the population.

Development of Food Pattern Recommendations for Infants and Toddlers 6-24 Months of Age to Support the Dietary Guidelines for Americans, 2020-2025.

BACKGROUND: Developing food-based dietary guidelines (FBDGs) for infants and toddlers is a complex task that few countries have attempted. OBJECTIVES: Our objectives are to describe the process of food pattern modeling (FPM) conducted to develop FBDGs for the Dietary Guidelines for Americans, 2020-2025 for infants 6 to <12 mo and toddlers 12 to <24 mo of age, as well as the implications of the results and areas needing further work. METHODS: The US 2020 Dietary Guidelines Advisory Committee, with the support of federal staff, conducted FPM analyses using 5 steps: 1) identified energy intake targets; 2) established nutritional goals; 3) identified food groupings and expected amounts, using 3 options for the amount of energy from human milk in each age interval; 4) estimated expected nutrient intakes for each scenario, based on nutrient-dense representative foods; and 5) evaluated expected nutrient intakes against nutritional goals. RESULTS: For human milk-fed infants (and toddlers), example combinations of complementary foods and beverages were developed that come close to meeting almost all nutrient recommendations if iron-fortified infant cereals are included at 6 to <12 mo of age. These combinations would also be suitable for formula-fed infants. For toddlers not fed human milk, 2 patterns were developed: the Healthy US-Style Pattern and the Healthy Vegetarian Pattern (a lacto-ovo vegetarian pattern). Achieving nutrient recommendations left virtually no remaining energy for added sugars. CONCLUSIONS: It is challenging to meet all nutrient needs during these age intervals. Added sugars should be avoided for infants and toddlers <2 y of age. Further work is needed to 1) establish a reference human milk composition profile, 2) update and strengthen the DRI values for these age groups, and 3) use optimization modeling, in combination with FPM, to identify combinations of foods that meet all nutritional goals.

Establishing What Constitutes a Healthy Human Gut Microbiome: State of the Science, Regulatory Considerations, and Future Directions.

On December 17, 2018, the North American branch of the International Life Sciences Institute (ILSI North America) convened a workshop "Can We Begin to Define a Healthy Gut Microbiome Through Quantifiable Characteristics?" with >40 invited academic, government, and industry experts in Washington, DC. The workshop objectives were to 1) develop a collective expert assessment of the state of the evidence on the human gut microbiome and associated human health benefits, 2) see if there was sufficient evidence to establish measurable gut microbiome characteristics that could serve as indicators of "health," 3) identify short- and long-term research needs to fully characterize healthy gut microbiome-host relationships, and 4) publish the findings. Conclusions were as follows: 1) mechanistic links of specific changes in gut microbiome structure with function or markers of human health are not yet established; 2) it is not established if dysbiosis is a cause, consequence, or both of changes in human gut epithelial function and disease; 3) microbiome communities are highly individualized, show a high degree of interindividual variation to perturbation, and tend to be stable over years; 4) the complexity of microbiome-host interactions requires a comprehensive, multidisciplinary research agenda to elucidate relationships between gut microbiome and host health; 5) biomarkers and/or surrogate indicators of host function and pathogenic processes based on the microbiome need to be determined and validated, along with normal ranges, using approaches similar to those used to establish biomarkers and/or surrogate indicators based on host metabolic phenotypes; 6) future studies measuring responses to an exposure or intervention need to combine validated microbiome-related biomarkers and/or surrogate indicators with multiomics characterization of the microbiome; and 7) because static genetic sampling misses important short- and long-term microbiome-related dynamic changes to host health, future studies must be powered to account for inter- and intraindividual variation and should use repeated measures within individuals.

Considerations for best practices in studies of fiber or other dietary components and the intestinal microbiome.

A 2-day workshop organized by the National Institutes of Health and U.S. Department of Agriculture included 16 presentations focused on the role of diet in alterations of the gastrointestinal microbiome, primarily that of the colon. Although thousands of research projects have been funded by U.S. federal agencies to study the intestinal microbiome of humans and a variety of animal models, only a minority addresses dietary effects, and a small subset is described in sufficient detail to allow reproduction of a study. Whereas there are standards being developed for many aspects of microbiome studies, such as sample collection, nucleic acid extraction, data handling, etc., none has been proposed for the dietary component; thus this workshop focused on the latter specific point. It is important to foster rigor in design and reproducibility of published studies to maintain high quality and enable designs that can be compared in systematic reviews. Speakers addressed the influence of the structure of the fermentable carbohydrate on the microbiota and the variables to consider in design of studies using animals, in vitro models, and human subjects. For all types of studies, strengths and weaknesses of various designs were highlighted, and for human studies, comparisons between controlled feeding and observational designs were discussed. Because of the lack of published, best-diet formulations for specific research questions, the main recommendation is to describe dietary ingredients and treatments in as much detail as possible to allow reproduction by other scientists.

Dietary and Complementary Feeding Practices of US Infants, 6 to 12 Months: A Narrative Review of the Federal Nutrition Monitoring Data.

Complementary foods and beverages (CFBs) are key components of an infant's diet in the second 6 months of life. This article summarizes nutrition and feeding practices examined by the 2020 Dietary Guidelines Advisory Committees during the CFB life stage. Breastfeeding initiation is high (84%), but exclusive breastfeeding at 6 months (26%) is below the Healthy People 2030 goal (42%). Most infants (51%) are introduced to CFBs sometime before 6 months. The primary mode of feeding (ie, human milk fed [HMF]; infant formula or mixed formula and human milk fed [FMF]) at the initiation of CFBs is associated with the timing of introduction and types of CFBs reported. FMF infants (42%) are more likely to be introduced to CFBs before 4 months compared with HMF infants (19%). Different dietary patterns, such as higher prevalence of consumption and mean amounts, were observed, including fruit, grains, dairy, proteins, and solid fats. Compared with HMF infants of the same age, FMF infants consume more total energy (845 vs 631 kcal) and protein (22 vs 12 g) from all sources, and more energy (345 vs 204 kcal) and protein (11 vs 6 g) from CFBs alone. HMF infants have a higher prevalence of risk of inadequate intakes of iron (77% vs 7%), zinc (54% vs <3%), and protein (27% vs <3%). FMF infants are more likely to have an early introduction (<12 months) to fruit juice (45% vs 20%) and cow's milk (36% vs 24%). Registered dietitian nutritionists and nutritional professionals should consider tailoring their advice to caregivers on dietary and complementary feeding practices, taking into account the primary mode of milk feeding during this life stage to support infants' nutrient adequacy. National studies that address the limitations of this analysis, including small sample sizes and imputed breast milk volume, could refine findings from this analysis.

Perspective: Framework for Developing Recommended Intakes of Bioactive Dietary Substances.

Dietary bioactives are food substances that promote health but are not essential to prevent typical deficiency conditions. Examples include lutein and zeaxanthin, omega-3 fatty acids, and flavonoids. When quality evidence is available, quantified intake recommendations linking dietary bioactives with specific health benefits will enable health professionals to provide evidence-based information to consumers. Without evidence-based recommendations, consumers use information from available sources that often lack standards and rigor. This article describes a framework to develop guidance based on quality evidence fully vetted for efficacy and safety by qualified experts, and designed to communicate the amounts of specific dietary bioactive compounds with identified health benefits. The 4-step Framework described here can be adapted by credible health organizations to work within their guideline development process. Standards of practice used in clinical guidelines are adapted to quantify dietary bioactive intake recommendations from foods consumed by the general public, by taking into account that side effects and trade-offs are often needed for medical treatments but are not acceptable for dietary bioactives. In quantifying dietary bioactive recommendations, this Framework establishes 4 decision-making steps: 1) characterize the bioactive, determine amounts in specific food sources, and quantify intakes; 2) evaluate safety; 3) quantify the causal relation between the specific bioactive and accepted markers of health or normal function via systematic evidence reviews; and 4) translate the evidence into a quantified bioactive intake statement. This Framework provides a working model that can be updated as new approaches are advanced.

Perspective: Impact of the National Academy of Sciences, Engineering, and Medicine Report on the Process for the 2020 Dietary Guidelines Advisory Committee.

The National Academy of Sciences, Engineering, and Medicine (NASEM) recommended steps to redesign the process of developing the Dietary Guidelines for Americans (DGA) are based on 5 guiding principles (enhance transparency; promote diversity of expertise and experience; support a deliberative process; manage biases and conflicts of interest; and adopt state-of-the-art processes and methods). Using these principles and recommendations, the USDA and HHS updated the process for developing the 2020-2025 Dietary Guidelines, including the process for appointing members and managing the work of the 2020 Dietary Guidelines Advisory Committee. Modifications included having public comment on the topics and questions to be addressed by the Federal Advisory Committee, reviewing professional and financial activities on potential appointees to the committee prior to their appointment, redesigning the website to provide status updates on the work of the committee as analytical frameworks and draft conclusions were developed, strengthening the approaches for conducting systematic reviews, and adding a public meeting for discussion of the final report before its submission to the Secretaries of the USDA and HHS. Because the DGA is reviewed and updated every 5 y, it is possible to learn from each cycle what works well and where improvements in the process can be implemented. The current article illustrates, from the perspective of the advisory committee, the impact of the NASEM report on the development of the scientific report by examining changes in the process consistent with the 5 principles.

Scientific rigor and credibility in the nutrition research landscape.

Scientific progress depends on the quality and credibility of research methods. As discourse on rigor, transparency, and reproducibility joins the cacophony of nutrition information and misinformation in mass media, buttressing the real and perceived reliability of nutrition science is more important than ever. This broad topic was the focus of a 2016 plenary session, "Scientific Rigor and Competing Interests in the Nutrition Research Landscape." This article summarizes and expands on this session in an effort to increase understanding and dialogue with regard to factors that limit the real and perceived reliability of nutrition science and steps that can be taken to mitigate those factors. The end goal is to both earn and merit greater trust in nutrition science by both the scientific community and the general public. The authors offer suggestions in each of the domains of education and training, communications, research conduct, and procedures and policies to help achieve this goal. The authors emphasize the need for adequate funding to support these efforts toward greater rigor and transparency, which will be resource demanding and may require either increased research funding or the recognition that a greater proportion of research funding may need to be allocated to these tasks.

Postprandial Metabolism of Macronutrients and Cardiometabolic Risk: Recent Developments, Emerging Concepts, and Future Directions.

Cardiovascular disease (CVD) is the leading cause of death in the United States. Although the role of habitual lifestyle factors such as physical activity and dietary patterns in increasing CVD risk has long been appreciated, less is known about how acute daily activities may cumulatively contribute to long-term disease risk. Here, the term acute refers to metabolic responses occurring in a short period of time after eating, and the goal of this article is to review recently identified stressors that can occur after meals and during the sleep-wake cycle to affect macronutrient metabolism. It is hypothesized that these events, when repeated on a regular basis, contribute to the observed long-term behavioral risks identified in population studies. In this regard, developments in research methods have supported key advancements in 3 fields of macronutrient metabolism. The first of these research areas is the focus on the immediate postmeal metabolism, spanning from early intestinal adsorptive events to the impact of incretin hormones on these events. The second topic is a focus on the importance of meal components on postprandial vasculature function. Finally, some of the most exciting advances are being made in understanding dysregulation in metabolism early in the day, due to insufficient sleep, that may affect subsequent processing of nutrients throughout the day. Key future research questions are highlighted which will lead to a better understanding of the relations between nocturnal, basal (fasting), and early postmeal events, and aid in the development of optimal sleep and targeted dietary patterns to reduce cardiometabolic risk.

Plasma cholecystokinin is associated with subjective measures of satiety in women.

BACKGROUND: Cholecystokinin is associated with satiety. Fat stimulates cholecystokinin release, and fiber appears to prolong cholecystokinin elevation during the alimentary period. OBJECTIVE: We tested whether adding fiber or fat to a low-fat, low-fiber meal increases cholecystokinin release and enhances subjective measures of satiety and whether the cholecystokinin response correlates with subjective measures of satiety. DESIGN: Three isoenergetic breakfast meals were tested in a randomized crossover design: low fiber, low fat; high fiber, low fat; and low fiber, high fat. Blood samples were drawn from fasted subjects (7 men and 8 women) before and at different time points after test meal consumption for 6 h. Plasma was analyzed for cholecystokinin, insulin, glucose, and triacylglycerols. Visual analogue scales were used to assess subjects' hunger, desire to eat, fullness, and prospective consumption. RESULTS: In the women, the meals higher in fiber or in fat resulted in greater feelings of satiety and in significantly higher cholecystokinin responses than did the low-fat, low-fiber meal. In the men, the increase in cholecystokinin concentration did not differ between meals, but the 2 low-fat meals elicited a greater feeling of satiety than did the high-fat meal. The insulin response was significantly higher for the low-fiber, low-fat meal than for the other 2 meals, and the triacylglycerol response was greatest for the high-fat, low-fiber meal. CONCLUSION: In women, the feeling of satiety caused by cholecystokinin release is enhanced by increasing either the fiber or fat content of a low-fat, low-fiber meal.

Interaction of fat availability and sex on postprandial satiety and cholecystokinin after mixed-food meals.

BACKGROUND: Cholecystokinin (CCK) is associated with fat-induced satiety. OBJECTIVE: The primary objective of the present study was to determine, in an acute meal setting, whether the availability of dietary fat for alimentary processing, and hence the stimulation of CCK, affects the postmeal satiety response in men and women. DESIGN: In a within-subjects design, subjects (8 men, 7 women) consumed 1 of 3 isoenergetic mixed-food test meals 1 wk apart in random order. The test meals contained 30% of energy from fat, of which more than two-thirds was derived from whole almonds, almond oil, or a mix of safflower and corn oils. Visual analogue scales were used to assess indexes of satiety at defined time points up to 6 h after meal consumption. Blood was sampled at corresponding time points for measurement of CCK, glucose, insulin, and triacylglycerol. Subsequent food intake was also assessed. RESULTS: All meals suppressed hunger and induced a pattern of satiety that was sex-specific and corresponded with the CCK response. Women had higher plasma CCK concentrations and experienced greater satiety after the almond oil and control meals (fat as oil) than after the whole almond meal (fat in whole food structure). Men showed no differential response among meals for CCK and satiety. Plasma triacylglycerol differed by time among meals but not by sex, and no significant differences in glucose and insulin were found. CONCLUSIONS: The satiety response to dietary fat provided in oil or whole food form is influenced by sex and is dependent on the availability of fat to stimulate CCK release in women but not in men.

Evolution of dietary guidelines.

Advice on eating behavior, food choices, and food preparation have been incorporated into philosophical and religious writings over the ages; however, in the past 150 years, these recommendations have been based on science related to public health policy and medicine. In the first half of the 20th century, the focus was on sanitation and prevention of nutrient deficiency diseases. In the second half, the focus has shifted to prevention of chronic disease and dietary excesses that increase disease risk. Current guidelines recognize the importance of lifestyle as well as food and nutrition choices. Dietary guidelines that were developed in the early 1980s emphasized components of food such as saturated fat, individual nutrients, or fiber. Revisions of these guidelines have placed more emphasis on food choices rather than individual nutrients, and recommendations have become more food-based. The process developed by the Food and Agricultural Organization and World Health Organization for preparation and use of food-based dietary guidelines begins with analysis of the most critical public health issues that are related to diet and outlines strategies to identify food-based approaches to address these issues. Countries that have implemented this process indicate that consensus building accomplished through the process has allowed a multisector approaches for addressing diet-related public health problems.

Strategies to optimize the impact of nutritional surveys and epidemiological studies.

The development of nutrition and health guidelines and policies requires reliable scientific information. Unfortunately, theoretical considerations and empirical evidence indicate that a large percentage of science-based claims rely on studies that fail to replicate. The session "Strategies to Optimize the Impact of Nutrition Surveys and Epidemiological Studies" focused on the elements of design, interpretation, and communication of nutritional surveys and epidemiological studies to enhance and encourage the production of reliable, objective evidence for use in developing dietary guidance for the public. The speakers called for more transparency of research, raw data, consistent data-staging techniques, and improved data analysis. New approaches to collecting data are urgently needed to increase the credibility and utility of findings from nutrition epidemiological studies. Such studies are critical for furthering our knowledge and understanding of the effects of diet on health.

Gastrointestinal physiology and functions.

While the health benefit of a functional food may be a metabolic response that lowers risk for disease, the actual target for the food or food component may be on the functioning of the gastrointestinal tract (GIT). For example, slowing absorption from the intestine, as measured by examining the appearance of the nutrient or food component in the blood, the hormone response associated with absorption of the compound or excretion of the compound, may provide a health benefit. However, the food component may slow absorption by delaying gastric emptying, altering the mixing within the intestinal contents or decreasing the availability of digestive enzymes in the intestine. These measures of GIT function provide validation of the mechanisms by which the functional food or food components affect metabolism. Bioavailability of physiologically active compounds from foods will be determined by the digestibility of foods that contain these compounds, their subsequent absorption and utilization by tissues. The physical structure of foods contributes to the functional effects of foods as well as to the availability of compounds from foods. For example, recent studies have demonstrated that changing the viscosity of the gut contents alters absorption and GIT response. Additionally, food structures such as the plant cell wall change the availability of absorbable compounds along the gastrointestinal contents. The areas of probiotics and prebiotics have highlighted the potential importance of gut microflora in health. While evidence suggests biological activity relevant to disease risk reduction, the long-term implications of the microbial activity have yet to be established.

Incorporating dairy foods into low and high fat diets increases the postprandial cholecystokinin response in men and women.

The postprandial period is a dynamic state of hormone and lipoprotein metabolism that can be influenced by dietary composition. The objective of this study was to determine whether the source of dietary fat [dairy (D) vs. nondairy (ND)] would modify the lipemic, insulin and cholecystokinin (CCK) response to high or low fat meals. Men and women (n = 24) consumed 4 test meals with a similar polyunsaturated:saturated (P:S; 0.12:1) fat ratio. The diets were high (38% energy) or low (20% energy) in fat, with or without fat from dairy sources. CCK responses were greater after consumption of meals containing D than ND, and for high compared with low fat meals. Women had higher CCK responses than men and were more sensitive to the differences in dietary treatments. Consumption of low fat meals resulted in greater insulin responses than high fat meals. However, after consumption of the low fat meals, the insulin response of D was about half of the ND response; no differences in insulin response were detected after the high fat meals. Triacylglyceride response was influenced primarily by the fat content of the diet. Consumption of dairy products containing fat was associated with an enhanced CCK response, which may have implications for the regulation of food intake. Blunting glucose and insulin response in low fat meals containing fat from dairy products may be useful for glycemic control.

Almonds and almond oil have similar effects on plasma lipids and LDL oxidation in healthy men and women.

Epidemiologic and clinical studies have shown that nut consumption is associated with favorable plasma lipid profiles and reduced cardiovascular risk. These effects may result from their high monounsaturated fat (MUFA) content but nuts contain constituents other than fatty acids that might be cardioprotective. We conducted a study to compare the effects of whole-almond vs. almond oil consumption on plasma lipids and LDL oxidation in healthy men and women. Using a randomized crossover trial design, 22 normolipemic men and women replaced half of their habitual fat (approximately 14% of approximately 29% energy) with either whole almonds (WA) or almond oil (AO) for 6-wk periods. Compliance was ascertained by monitoring dietary intake via biweekly 5-d food records, return of empty almond product packages and weekly meetings with a registered dietitian. Fat replacement with either WA and AO resulted in a 54% increase in percentage of energy as MUFA with declines in both saturated fat and cholesterol intake and no significant changes in total energy, total or polyunsaturated fat intake. The effects of WA and AO on plasma lipids did not differ compared with baseline; plasma triglyceride, total and LDL cholesterol significantly decreased, 14, 4 and 6% respectively, whereas HDL cholesterol increased 6%. Neither treatment affected in vitro LDL oxidizability. We conclude that WA and AO do not differ in their beneficial effects on the plasma lipid variables measured and that this suggests that the favorable effect of almonds is mediated by components in the oil fraction of these nuts.