Advances in Nutrition: An International Review Journal current issue

The History and Future of Dietary Guidance in America

AbstractEvidence-based dietary guidance in the United States has progressed substantially since its inception >100 y ago. This review describes the historical development and significance of dietary guidance in the United States, including the Dietary Guidelines for Americans (DGAs), and emphasizes the foundations upon which they were developed, the process in the formation of past and current guidelines, and present and future applications. Dietary guidance during the first half of the 20th century was focused primarily on food groups in a healthy diet, food safety, safe food storage, and the role of some minerals and vitamins in the prevention of disease. This was punctuated by World War II messaging to reduce food waste and increase food storage. In 1980, the first DGA report was released, and later, the USDA and the Department of Health and Human Services (HHS) were given a mandate for reissuance and reassessment every 5 y. An ad hoc advisory committee made up of nongovernmental experts was established for each edition to review the scientific evidence and provide content recommendations to the Secretaries of the USDA and the HHS. Wording was changed from negative (avoid) to positive (choose) and emphasis was increasingly placed on reducing the prevalence of overweight and obesity and prevention of chronic diseases. Today, the DGAs guide all federally funded feeding and educational programs, including food policies, food assistance programs, and consumer education programs, as well as these programs at the regional, state, and local levels. Additional users include dietitians and other health professionals, food service personnel, food and beverage manufacturers, schools, and day care facilities. Currently, the DGAs are intended for individuals aged ≥2 y. Future editions of the DGAs will include guidance for infants and children <2 y, as well as pregnant women.

Perspective: Challenges and Controversial Issues in the Dietary Guidelines for Americans, 1980–2015

AbstractSince 1980, every edition of the Dietary Guidelines for Americans (DGAs) has recommended increased consumption of fruits, vegetables, and whole grains, but reduced consumption of saturated fat, sugars, and sodium and, therefore, their primary food sources. Every edition has generated controversy, mainly from producers of foods affected by “eat less” recommendations, particularly meat. Objections to the 2015 DGAs focused on environmental as well as scientific issues, but also on purported conflicts of interest among members of the Dietary Guidelines Advisory Committee. On this basis, critics induced Congress to authorize the National Academy of Medicine (NAM) to review the process of drawing up the guidelines. The NAM's 2017 reports should strengthen the process, but as long as science continues to support advice to reduce consumption of targeted foods, the guidelines will continue to elicit political controversy.

Obesity Interventions for Older Adults: Diet as a Determinant of Physical Function

AbstractThroughout the world, a high prevalence of obesity in older populations has created a new phenotype of frailty: the obese, functionally frail older adult. The convergence of the obesity epidemic with global graying will undoubtedly increase the prevalence of this concern. Barriers to treatment include ambiguities about the appropriate level of obesity that should trigger an intervention, due to age-related physiologic changes and a lack of consensus on specific criteria and cutoffs. Moreover, obesity interventions for this population have been limited by concerns about negative effects on lean mass, bone mineral density, and even mortality. However, newly reported approaches for restoring physical function by obesity reduction have shown good short-term efficacy. Because the majority of these interventions have used exercise as part of the treatment, this review focuses specifically on current understanding of the discrete effects of dietary interventions for geriatric obesity with regards to functional outcomes on tests including the Short Physical Performance Battery, the Physical Performance Test, and the Western Ontario and McMaster Universities Osteoarthritis Index. The literature showed roughly equal benefits to function from a weight reduction diet or exercise regimen, although neither modality was as efficacious alone as the 2 combined. Only 1 of 3 studies of protein intake during weight loss showed a positive effect of protein on function, but findings to date are too limited to prove or disprove a protein benefit. We conclude that although diet and exercise should be combined whenever possible, it remains important to further investigate the beneficial and likely unique effects that calorie restriction and/or nutrient modification can provide, particularly for obese and functionally frail older populations.

Perspective: Total, Added, or Free? What Kind of Sugars Should We Be Talking About?

AbstractThere is consistent public guidance to limit sugars intakes. However, WHO recommendations are for “free” sugars, whereas some other guidance documents and public discussion focus on “added” sugars, and globally most food labeling states “total” sugars. Total sugars comprise all mono- and disaccharides, regardless of source, whereas both added and free sugars exclude the sugars that naturally occur in dairy products and intact fruit and vegetables. Definitions of added and free sugars differ mainly in their respective exclusion or inclusion of sugars in juiced or pureed fruit and vegetables. To date, there has been little evidence-based analysis of the scientific basis for these different sugar classifications or implications of their adoption for consumer communication and nutrition labeling. Evidence of discriminating relations of total compared with added or free sugars with weight gain or energy intake, type 2 diabetes, and dental caries was identified from recent systematic reviews and meta-analyses. The relations were weakest for total sugars and most consistent for dietary sources corresponding to free sugars (including sugars added to and in fruit juices). Consideration of these health outcomes suggests that the emphasis for intake monitoring, public health guidance, and consumer communication should be on free sugars. However, at present, the adoption of free sugars for these purposes would also carry challenges related to implementation, including consumer understanding, consensus on specifications, and current (labeling) regulations.

Perspective: Cardiovascular Responses to Sugar-Sweetened Beverages in Humans: A Narrative Review with Potential Hemodynamic Mechanisms

AbstractCardiovascular diseases are still the primary cause of mortality worldwide, with high blood pressure and type 2 diabetes as major promoters. Over the past 3 decades, almost in parallel with the rise in cardiovascular disease incidence, the consumption of sugar-sweetened beverages (SSBs) has increased. In this context, SSBs are potential contributors to weight gain and increase the risk for elevations in blood pressure, type 2 diabetes, coronary heart disease, and stroke. Nevertheless, the mechanisms underlying the cardiovascular and metabolic responses to SSBs, in particular on blood pressure, are poorly understood. We discuss and propose potential mechanisms underlying differential effects of sugars on postprandial blood pressure regulation; provide evidence for additional molecular contributors, i.e., fibroblast growth factor 21, towards sugar-induced cardiovascular responses; and discuss potential cardiovascular neutral sugars. Furthermore, we explore whether pre-existing glucose intolerance in humans exacerbates the cardiovascular responses to SSBs, thus potentially aggravating the cardiovascular risk in already-susceptible individuals.

Can Curcumin Counteract Cognitive Decline? Clinical Trial Evidence and Rationale for Combining ω-3 Fatty Acids with Curcumin

AbstractThe rate of cognitive decline in the elderly is highly variable. One potential factor contributing to accelerated cognitive decline is chronic systemic inflammation, because it has been linked to cognitive impairment and increased dementia risk. Certain lifestyle factors, such as excess body weight and sedentary behavior, can exacerbate a proinflammatory state in older adults, resulting in chronic low-grade inflammation. Supplementing the diet with curcumin, an anti-inflammatory polyphenolic compound from the curry spice turmeric, is a potential approach to prevent accelerated cognitive decline by counteracting chronic inflammatory processes. Although the anti-inflammatory effects of curcumin are well established, the potential cognitive benefits of curcumin were discovered more recently. Several animal and epidemiologic studies on the effect of curcumin supplementation on cognition showed promising results; however, randomized controlled trials in humans are limited. In this review, we identified 5 randomized controlled trials, of which only 2 observed a beneficial effect of curcumin supplementation on cognition by improving working memory. By critically examining the methodologies of those studies, we identified some limitations, one of which is that none of the studies explored the possibility that anti-inflammatory mechanisms were mediating cognitive benefits (i.e., no study tested participants with low-grade inflammation or measured inflammatory biomarkers). Other factors influencing the likelihood of conclusive outcomes include choice of study population (cognitively unimpaired compared with impaired), study duration, curcumin dose and its bioavailability, and neurocognitive test battery. On the basis of these findings, we offer recommendations for future studies to examine the potential cognitive benefits of curcumin in humans, which include evaluating its effects on cerebral endothelial vasodilator function and boosting its cognitive effects by combining it with long-chain omega-3 (n–3) fatty acids.

Bone Health following Bariatric Surgery: Implications for Management Strategies to Attenuate Bone Loss

AbstractBariatric surgery (BS) is an effective treatment for morbid obesity and its associated comorbidities. Following such a procedure, however, patients are at risk of developing metabolic bone disease owing to the combination of rapid weight loss, severely restricted dietary intake, and reduced intestinal nutrient absorption. Patients undergoing malabsorptive procedures are at a higher risk of postoperative bone health deterioration than those undergoing restrictive procedures; however, studies have demonstrated negative skeletal consequences of restrictive procedures as well. The clinical practice guidelines of some international associations have previously addressed preoperative evaluation and postoperative clinical care in order to maintain bone health in BS patients. Nevertheless, some issues regarding bone health in BS patients remain unclear owing to the lack of relevant randomized clinical trials, including doses of nutritional supplements pre- and post-BS. This review summarizes the current data regarding the skeletal consequences of BS and its mechanisms, with an emphasis on the preventive strategies and nutritional care that may be warranted in order to attenuate bone deterioration following BS.

Nutritional Genomics and Direct-to-Consumer Genetic Testing: An Overview

AbstractThe increasing prevalence in polygenic diseases, such as obesity, cardiovascular disease, and type 2 diabetes, observed over the past few decades is more likely linked to a rapid transition in lifestyle rather than to changes in the sequence of the nuclear genome. In the new era of precision medicine, nutritional genomics holds the promise to be translated into tailored nutritional strategies to prevent and manage polygenic diseases more effectively. Nutritional genomics aims to prevent, treat, and manage polygenic diseases through targeted therapies formulated from individuals’ genetic makeup and dietary intake. Direct-to-consumer genetic testing (DTC-GT) has become commercially available to equip individuals with information on their genetic vulnerability to different diseases. This information may potentially prompt behavioral changes against adverse factors. However, scientific evidence behind the clinical recommendations is a matter of continuous debate, and behavioral modifications after disclosing genetic information remain inconclusive. In this review, we provide an overview of nutritional genomics and related nutritional DTC-GT services and discuss whether available data are sufficient to be translated into clinical recommendations and public health initiatives. Overall, the scientific evidence supporting the dissemination of genomic information for nutrigenomic purposes remains sparse. Therefore, additional knowledge needs to be generated, particularly for polygenic traits.

Review of 100% Fruit Juice and Chronic Health Conditions: Implications for Sugar-Sweetened Beverage Policy

AbstractWhether or not drinking 100% fruit juice causes poor health is controversial. Although 100% fruit juice may contain as much sugar as regular soda, it provides needed nutrients to Americans’ diets. We systematically reviewed the current evidence of the association of 100% fruit juice consumption and chronic health conditions in children and adults. We focused on data from systematic reviews and meta-analyses about cardiometabolic health outcomes, liver disease, and caries. Aside from increased risk of tooth decay in children and small amounts of weight gain in young children and adults, there is no conclusive evidence that consumption of 100% fruit juice has adverse health effects. Guidelines from groups like the American Academy of Pediatrics and Dietary Guidelines for Americans recommending that 100% fruit juice may be consumed in moderation are consistent with the available evidence and should be used to inform food policies.

Snacking Recommendations Worldwide: A Scoping Review

AbstractAcross the globe, dietary habits include the consumption of foods and drinks between main meals. Although often described as “snacks” or “snacking,” there is no scientific consensus of what constitutes a snack, either as an eating occasion or as a snack food. Nonetheless, food-based dietary guidelines, compiled at national or regional levels by governments, learned societies, and health organizations, frequently refer to snacking habits and desirable or undesirable snack food choices. This review aims to provide a comprehensive snapshot of snacking recommendations worldwide. From a search of 207 countries and organizations, 49 countries and 7 regional or global organizations were identified that referred to snacks, snack foods, or snacking. A total of 136 snacking-specific recommendations or examples were identified, which varied in nature whereby some provided advice on the quality of the snack food choice and others focused on the frequency or energy and nutrient composition of such snacks. Guidelines varied in terms of the detail of foods and drinks identified, wherein some recommendations focused only on foods or food categories to include (e.g., fruit or dairy) or to exclude (e.g., processed foods), whereas other recommendations made reference to both. Both individual foods (e.g., apples) and food categories (e.g., fruit) were mentioned. Reasons or rationales to support the snacking choices were less frequently identified and varied across regions. It is hoped that this analysis will stimulate discussion on the need for a consensus in the scientific community and beyond with regard to snacking. An agreed-upon definition of snacks, snacking, and snack foods could be used to inform a number of stakeholders and ultimately help consumers adhere to healthful diets as defined locally.

ω-3 Fatty Acids, Impaired Fetal Growth, and Cardiovascular Risk: Nutrition as Precision Medicine

AbstractPrecision medicine refers to treatment or prevention strategies in a group of individuals identified by their phenotype or genotype. Dietary components or patterns may play an important role in precision medicine. There is emerging evidence to support a role for n–3 (ω-3) fatty acids in lowering blood pressure and reducing the extent of subclinical atherosclerosis in people born with impaired fetal growth, a group at increased risk of coronary artery disease partly due to an increased risk of hypertensive disorders. The evidence linking n–3 fatty acid intake with less atherosclerosis and lower blood pressure in people with impaired fetal growth has been derived from studies in young children, adolescents, and adults and has included dietary assessments by questionnaires and circulating biomarkers. Furthermore, results appear to be similar for shorter chain n–3 fatty acids from plant sources and long-chain n–3 fatty acids from marine sources. The general framework used to develop this evidence, consisting of hypothesis-driven analyses from observational studies and post hoc analyses of a randomized clinical trial, before a priori testing as a primary outcome in randomized trials, is presented and proposed as a potential model for the identification and development of dietary precision medicine strategies.

Backpack Programs and the Crisis Narrative of Child Hunger—A Critical Review of the Rationale, Targeting, and Potential Benefits and Harms of an Expanding but Untested Model of Practice

AbstractIn recent years, school-based food backpack programs (BPPs) have come into national prominence as a response to a perceived crisis of child hunger in America. Distributing bags of free food directly to schoolchildren for their own personal consumption each weekend, BPPs bring together private donors, faith communities, and public schools around an intuitively appealing project: children are hungry, and so we give them food. Perhaps because of their intuitive appeal, BPPs have expanded rapidly, without rigorous evaluation to determine their impacts on children, families, and schools. This Perspective aims to open up thinking about BPPs, first articulating the implicit conceptual model that undergirds BPPs, drawing on documentation offered by major program providers and on our own experience working with several schools implementing BPPs, to provide a window into what BPPs do and how and why they do it. We focus in particular on how the crisis narrative of child hunger has shaped the BPP model and on the related interplay between public sympathy and the neoliberal climate in which structural solutions to family poverty are eschewed. We then assess the BPP model in light of existing knowledge, concluding that BPPs fit poorly with the needs of the majority of children living in food-insecure households in the United States and consequently put children at risk of negative consequences associated with worry, shame, stigma, and disruptions to family functioning. Finally, we provide recommendations for practice and research, emphasizing the importance of 1) responding to children's actual needs throughout program implementation, 2) avoiding unnecessary risks by effective targeting of services to only those children who need them, and 3) rigorously evaluating program outcomes and unintended consequences to determine whether, even for the small number of US children who experience hunger, the benefits of the BPP model outweigh its psychosocial costs.

Butyrate: A Double-Edged Sword for Health?

AbstractButyrate, a four-carbon short-chain fatty acid, is produced through microbial fermentation of dietary fibers in the lower intestinal tract. Endogenous butyrate production, delivery, and absorption by colonocytes have been well documented. Butyrate exerts its functions by acting as a histone deacetylase (HDAC) inhibitor or signaling through several G protein–coupled receptors (GPCRs). Recently, butyrate has received particular attention for its beneficial effects on intestinal homeostasis and energy metabolism. With anti-inflammatory properties, butyrate enhances intestinal barrier function and mucosal immunity. However, the role of butyrate in obesity remains controversial. Growing evidence has highlighted the impact of butyrate on the gut-brain axis. In this review, we summarize the present knowledge on the properties of butyrate, especially its potential effects and mechanisms involved in intestinal health and obesity.

Practical Dietary Recommendations for the Prevention and Management of Nonalcoholic Fatty Liver Disease in Adults

AbstractNonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. In the absence of effective pharmacotherapies, clinical guidelines focus primarily on weight loss to treat this condition. Established consensus, evidence-based, and clinical dietary recommendations for NAFLD are currently lacking. The aim of this paper is to provide evidence-based practical dietary recommendations for the prevention and management of NAFLD in adults. A literature review focusing on established principles for the development of clinical practice recommendations was employed using the following criteria: based on substantial evidence, ensures risk minimization, is flexible for an individual patient approach, and is open to further modification as evidence emerges. The Practice-based Evidence in Nutrition classification system was used to grade these principles. Five key dietary recommendations were developed: 1) follow traditional dietary patterns, such as the Mediterranean diet; 2) limit excess fructose consumption and avoid processed foods and beverages with added fructose; 3) PUFAs, especially long-chain omega-3 rich foods and MUFAs, should replace SFAs in the diet; 4) replace processed food, fast food, commercial bakery goods, and sweets with unprocessed foods high in fiber, including whole grains, vegetables, fruits, legumes, nuts, and seeds; and 5) avoid excess alcohol consumption. Improving diet quality may reduce the incidence and progression of NAFLD and associated risk factors. Many of the benefits are likely to result from the collective effect of dietary patterns. High-quality research—in particular, randomized clinical trials assessing dietary interventions that focus on liver-specific endpoints—are needed as a priority.

The Problem of Curcumin and Its Bioavailability: Could Its Gastrointestinal Influence Contribute to Its Overall Health-Enhancing Effects?

AbstractCurcumin, from the spice turmeric, exhibits anti-inflammatory, antioxidant, anticancer, antiviral, and neurotrophic activity and therefore holds promise as a therapeutic agent to prevent and treat several disorders. However, a major barrier to curcumin's clinical efficacy is its poor bioavailability. Efforts have therefore been dedicated to developing curcumin formulations with greater bioavailability and systemic tissue distribution. However, it is proposed in this review that curcumin's potential as a therapeutic agent may not solely rely on its bioavailability, but rather its medicinal benefits may also arise from its positive influence on gastrointestinal health and function. In this review, in vitro, animal, and human studies investigating the effects of curcumin on intestinal microbiota, intestinal permeability, gut inflammation and oxidative stress, anaphylactic response, and bacterial, parasitic, and fungal infections are summarized. It is argued that positive changes in these areas can have wide-ranging influences on both intestinal and extraintestinal diseases, and therefore presents as a possible mechanism behind curcumin's therapeutic efficacy.

Dietary Supplements with Antiplatelet Activity: A Solution for Everyone?

AbstractDietary supplements can have beneficial effects on a number of risk factors for cardiovascular diseases, and interest in the use of nonpharmacologic nutraceutical-based treatments for cardiovascular disorders is growing. The aim of this review is to present the role of dietary supplements with antiplatelet activity in the prophylaxis and treatment of cardiovascular disorders. In addition, this paper describes their effects on another very important element of hemostasis—blood coagulation. However, because controlled human clinical experiments are too limited to clearly identify the antiplatelet and anticoagulant properties of dietary supplements, used alone or in combination with classical antiplatelet therapy (e.g., with aspirin), most information in this article is based on in vitro studies. Therefore, it cannot be unequivocally stated whether dietary supplements are universally safe and bring benefits to all. Some authors suggest that blood platelet count and function should be monitored in patients taking such supplements, especially before and after surgery, as well as other hemostasis parameters such as coagulation times.