Nutrients, endpoints, and the problem of proof

Phenotypic flexibility in nutrition research to quantify human variability: building the bridge to personalised nutrition

Phenotypic flexibility is a methodology that accurately assesses health in terms of mechanistic understanding of the interrelationship of multiple metabolic and physiological processes. This starts from the perspective that a healthy person is better able to cope with changes in environmental stressors that affect homeostasis compared to people with a compromised health state. The term 'phenotypic flexibility' expresses the cumulative ability of overarching physiological processes to return to homeostatic levels after short-term perturbations. The concept of phenotypic flexibility to define biomarkers for nutrition-related health was introduced in 2009 in the area of health optimisation and prevention and delay of non-communicable disease. The core approach consists of the combination of imposing a challenge test to the body followed by time-resolved analysis of multiple biomarkers. This new approach may better facilitate nutritional health research in intervention studies since it may show effects on early derailed physiological markers and the biomarker response can be extended by perturbing the system, thereby making them more sensitive in detecting health effects from food and nutrition. At the same time, interindividual variation can also be extended and compressed by challenge tests, facilitating the bridge to personalised nutrition. This review will overview where the science is in this research arena and what the phenotypic flexibility potential is for the nutrition field.

Need for a nutrition-specific scientific paradigm for research quality improvement

Nutrition science has been criticised for its methodology, apparently contradictory findings and generating controversy rather than consensus. However, while certain critiques of the field are valid and informative for developing a more cogent science, there are also unique considerations for the study of diet and nutrition that are either overlooked or omitted in these discourses. The ongoing critical discourse on the utility of nutrition sciences occurs at a time when the burden of non-communicable cardiometabolic disease continues to rise in the population. Nutrition science, along with other disciplinary fields, is tasked with producing a translational evidence-base fit for the purpose of improving population and individual health and reducing disease risk. Thus, an exploration of the unique methodological and epistemic considerations for nutrition research is important for nutrition researchers, students and practitioners, to further develop an improved scientific discipline for nutrition. This paper will expand on some of the challenges facing nutrition research, discussing methodological facets of nutritional epidemiology, randomised controlled trials and meta-analysis, and how these considerations may be applied to improve research methodology. A pragmatic research paradigm for nutrition science is also proposed, which places methodology at its centre, allowing for questions over both how we obtain knowledge and research design as the method to produce that knowledge to be connected, providing the field of nutrition research with a framework within which to capture the full complexity of nutrition and diet.

Why context matters when changing the diet: A narrative review of placebo, nocebo, and psychosocial context effects and implications for outcome research and nutrition counselling

Placebo (PE) and nocebo effects (NE) have been subjects of systematic research in medicine and psychotherapy for many decades to distinguish between the (specific) pharmacological effect of medication and the (unspecific) effect of the context. Despite this significant research, the awareness, operationalisation, and reflection of the multiplicity of PE, NE, and psychosocial context effects (PSCE) is currently limited when researching outcomes of diet changes in studies without randomisation and placebo control. This neglection is critical as it could systematically influence outcomes by moderating and mediating them and thus reducing the validity and evidence base of these studies. Therefore, we performed a (non-systematic) narrative review (NR) on the following objectives: (1) present a concise overview about the relevance of PE, NE, and PSCE in medicine and nutrition research; (2) review the current state of research on reflecting context effects when studying diet changes; (3) provide useful theoretical foundations via consideration and integration of micro- and macro context effects; (4) operationalise as hypotheses the potential PE, NE, and PSCE which are specific for researching diet changes; and (5) derive their impact for future research as well as for nutrition counselling. The electronic search in this NR for objective (2) identified N = 5 publications and for objective (4) we found N = 61 articles retrieved in the first round of search, additional references were identified by a manual and snowball search among the cited references resulting finally in N = 37. This NR offers a synoptical basis to foster awareness and operationalisation of a variety of PE, NE, and PSCE. Interdisciplinary research teams should monitor these factors using, e.g., qualitative, mixed-method studies, process evaluation, item bank approaches, moderator and mediator analysis that might reveal substantially new insights, and outcomes of relevance to science and nutrition counselling. Nevertheless, the present NR has several limitations, especially as it is non-systematic, because it is a very heterogeneous field of research, in which the topic we are investigating is usually regarded as marginal and subordinate. Therefore, future research should conduct systematic reviews and particularly theory-based primary studies (experimental research) on hypotheses of PE, NE, and PSCE in outcome research in diet changes.

Breaking new frontiers: Assessment and re-evaluation of clinical trial design for nutraceuticals

Despite sophisticated study designs and measurement tools, we have yet to create an innovative space for diet and dietary supplements in the health care system. The path is challenging due to current hierarchies of scientific evidence and regulatory affairs. The role of the randomized, double-blind, placebo-controlled clinical trial (RCT) as a research approach functions well to characterize the benefits and risks of drugs but lacks the sensitivity to capture the efficacy and safety of nutraceuticals. While some facets of RCTs can be relevant and useful when applied to nutraceuticals, other aspects are limiting and potentially misleading when taken in their entirety. A differentiation between guidelines for evidence-based medicine and the evidence required for nutrition spotlight the need to reconceptualize constituents of the RCT and their applicability with relevance to health promotion. This perspective identifies the limitations of the traditional RCT to capture the complexities of nutraceuticals and proposes the N-of-1 as Level 1 evidence better suited for the proof of efficacy of nutraceuticals.

Natural Antioxidant Evaluation: A Review of Detection Methods

Antioxidants have drawn the attention of the scientific community due to being related to the prevention of various degenerative diseases. The antioxidant capacity has been extensively studied in vitro, and different methods have been used to assess its activity. However, the main issues related to studying natural antioxidants are evaluating whether these antioxidants demonstrate a key role in the biological system and assessing their bioavailability in the organism. The majority of outcomes in the literature are controversial due to a lack of method standardization and their proper application. Therefore, this study aims to compile the main issues concerning the natural antioxidant field of study, comparing the most common in vitro methods to evaluate the antioxidant activity of natural compounds, demonstrating the antioxidant activity in biological systems and the role of the main antioxidant enzymes of redox cellular signaling and explaining how the bioavailability of bioactive compounds is evaluated in animal models and human clinical trials.

The essentiality of nutrients: a challenge to methodological monism in the scientific substantiation of health claims

This paper analyzes the way in which the EFSA has addressed the limitations that the essentiality of nutrients presents to the requirement of obtaining evidence from RCTs for the scientific substantiation of health claims. By redefining the requirements to affirm causality in the case of essentiality of nutrients, the EFSA has constrained the debate on the relevance of different methodologies in the field of nutrition research. However, avoiding this methodological debate does not settle the controversy as to whether the EFSA's evidentiary hierarchy is the best for both investigating causal relationships in nutrition and for achieving social objectives such as fostering innovation and public health.

Nutrition to Optimise Human Health-How to Obtain Physiological Substantiation?

Demonstrating in an unambiguous manner that a diet, let alone a single product, 'optimizes' health, presents an enormous challenge. The least complicated is when the starting situation is clearly suboptimal, like with nutritional deficiencies, malnutrition, unfavourable lifestyle, or due to disease or ageing. Here, desired improvements and intervention strategies may to some extent be clear. However, even then situations require approaches that take into account interactions between nutrients and other factors, complex dose-effect relationships etc. More challenging is to substantiate that a diet or a specific product optimizes health in the general population, which comes down to achieve perceived, 'non-medical' or future health benefits in predominantly healthy persons. Presumed underlying mechanisms involve effects of non-nutritional components with subtle and slowly occurring physiological effects that may be difficult to translate into measurable outcomes. Most promising strategies combine classical physiological concepts with those of 'multi-omics' and systems biology. Resilience-the ability to maintain or regain homeostasis in response to stressors-is often used as proxy for a particular health domain. Next to this, quantifying health requires personalized strategies, measurements preferably carried out remotely, real-time and in a normal living environment, and experimental designs other than randomized controlled trials (RCTs), for example N-of-1 trials.

Fifteen Years of Regulating Nutrition and Health Claims in Europe: The Past, the Present and the Future

Suggestions that a food contains healthy ingredients or that it can provide beneficial effects upon consumption have been regulated in the EU since 2006. This paper describes the analysis of how this nutrition and health claim regulation has resulted in over 300 authorised claims and how the authorisation requirements and processes have affected the use of claims on foods. Five challenges are identified that negatively affect the current legislation dealing with nutrition and health claims: non-reviewed botanical claims (as well as on hold claims for infants and young children), the lack of nutrient profiles and the focus of claims on single ingredients, consumer understanding, research into health effects of nutrition and finally, enforcement. These challenges are shown to influence the goals of the regulation: protecting consumers from false and misleading claims and stimulating the development of a level playing field in the EU, to foster innovation. Tackling these political and scientific substantiation questions for health claims, together with continuously analysing the understanding and usage of claims by consumers and operators will ensure that the NHCR will stay effective, today and in the future.

How fragile are Mediterranean diet interventions? A research-on-research study of randomised controlled trials

Introduction

The Mediterranean diet (MD) is a traditional regional dietary pattern and a healthy diet recommended for the primary and secondary prevention of various diseases and health conditions. Results from the higher level of primary evidence, namely randomised controlled trials (RCTs), are often used to produce dietary recommendations; however, the robustness of RCTs with MD interventions is unknown.

Methods

A systematic search was conducted and all MD RCTs with dichotomous primary outcomes were extracted from PubMed. The fragility (FI) and the reverse fragility index (RFI) were calculated for the trials with significant and non-significant comparisons, respectively.

Results

Out of 27 RCTs of parallel design, the majority failed to present a significant primary outcome, exhibiting an FI equal to 0. The median FI of the significant comparisons was 5, ranging between 1 and 39. More than half of the comparisons had an FI <5, indicating that the addition of 1–4 events to the treatment arm eliminated the statistical significance. For the comparisons with an FI=0, the RFI ranged between 1 and 29 (Median RFI: 7). When the included RCTs were stratified according to masking, the use of a composite primary endpoint, sample size, outcome category, or dietary adherence assessment method, no differences were exhibited in the FI and RFI between groups, except for the RFI among different compliance assessment methods.

Conclusions

In essence, the present study shows that even in the top tiers of evidence hierarchy, research on the MD may lack robustness, setting concerns for the formulation of nutrition recommendations.

Nutrition and Lifestyle Interventions for Managing Parkinson's Disease: A Narrative Review

The etiology of Parkinson's disease (PD) is not fully understood, but environmental toxin overexposure, increased intestinal permeability, and dysbiosis related to nutrition and lifestyle habits are thought to be contributors. Considering these nutrition and lifestyle implications, there is a lack of practice-based programs utilizing interventions for managing symptoms or slowing the progression of the disease. The purpose of this narrative review was to identify relevant research related to nutrition and lifestyle interventions for PD, evaluate the research utilizing the evidence analysis process of the Academy of Nutrition and Dietetics to assess the quality of each research article, and group the research into categories. A grading of recommendations assessment, development and evaluation (GRADE) of either good, fair, limited, or not assignable was allocated to each category of research, including diet patterns, vitamin D, B-complex, omega-3 fatty acids, coenzyme Q10, probiotics, physical activity, stress, and sleep. An intervention based on the research presented in the review may be utilized for coaching people with PD on symptom management.

Macronutrient and Micronutrient Intake during Pregnancy: An Overview of Recent Evidence

Nutritional status during pregnancy can have a significant impact on maternal and neonatal health outcomes. Requirements for macronutrients such as energy and protein increase during pregnancy to maintain maternal homeostasis while supporting foetal growth. Energy restriction can limit gestational weight gain in women with obesity; however, there is insufficient evidence to support energy restriction during pregnancy. In undernourished women, balanced energy/protein supplementation may increase birthweight whereas high protein supplementation could have adverse effects on foetal growth. Modulating carbohydrate intake via a reduced glycaemic index or glycaemic load diet may prevent gestational diabetes and large-for-gestational-age infants. Certain micronutrients are also vital for improving pregnancy outcomes, including folic acid to prevent neural tube defects and iodine to prevent cretinism. Newly published studies support the use of calcium supplementation to prevent hypertensive disorders of pregnancy, particularly in women at high risk or with low dietary calcium intake. Although gaps in knowledge remain, research linking nutrition during pregnancy to maternofoetal outcomes has made dramatic advances over the last few years. In this review, we provide an overview of the most recent evidence pertaining to macronutrient and micronutrient requirements during pregnancy, the risks and consequences of deficiencies and the effects of supplementation on pregnancy outcomes.

Vitamin D testing and treatment: a narrative review of current evidence

Vitamin D testing and treatment is a subject of controversial scientific discussions, and it is challenging to navigate through the expanding vitamin D literature with heterogeneous and partially opposed opinions and recommendations. In this narrative review, we aim to provide an update on vitamin D guidelines and the current evidence on the role of vitamin D for human health with its subsequent implications for patient care and public health issues. Vitamin D is critical for bone and mineral metabolism, and it is established that vitamin D deficiency can cause rickets and osteomalacia. While many guidelines recommend target serum 25-hydroxyvitamin D (25[OH]D) concentrations of ≥50 nmol/L (20 ng/mL), the minimum consensus in the scientific community is that serum 25(OH)D concentrations below 25-30 nmol/L (10-12 ng/mL) must be prevented and treated. Using this latter threshold of serum 25(OH)D concentrations, it has been documented that there is a high worldwide prevalence of vitamin D deficiency that may require public health actions such as vitamin D food fortification. On the other hand, there is also reason for concern that an exploding rate of vitamin D testing and supplementation increases costs and might potentially be harmful. In the scientific debate on vitamin D, we should consider that nutrient trials differ from drug trials and that apart from the opposed positions regarding indications for vitamin D treatment we still have to better characterize the precise role of vitamin D for human health.

The Role of Vitamin D in Fertility and during Pregnancy and Lactation: A Review of Clinical Data

Vitamin D deficiency is common and there exists a huge gap between recommended dietary vitamin D intakes and the poor vitamin D supply in the general population. While vitamin D is important for musculoskeletal health, there are accumulating data suggesting that vitamin D may also be important for fertility, pregnancy outcomes and lactation. Significant changes in vitamin D metabolism during pregnancy such as increased production of the “active vitamin D hormone” calcitriol support the important role of vitamin D in this setting. Observational studies show that vitamin D deficiency is a risk marker for reduced fertility and various adverse pregnancy outcomes and is associated with a low vitamin D content of breast milk. Meta-analyses of randomized controlled trials (RCTs) document that physiological vitamin D supplementation during pregnancy is safe and improves vitamin D and calcium status, thereby protecting skeletal health. Although certain RCTs and/or meta-analyses reported some other beneficial effects, it is still not clear whether vitamin D supplementation improves fertility or decreases the risk of adverse pregnancy outcomes such as low birth weight, pre-eclampsia and neonatal mortality, or reduces wheeze/asthma in the infants. Nevertheless, vitamin D supplementation in pregnant women is frequently required to achieve a sufficient vitamin D status as recommended by nutritional vitamin D guidelines. In this review, we provide an overview of systematic reviews, meta-analyses and large trials reporting clinical data on the role of vitamin D for fertility, pregnancy and lactation.

Perspective: Fundamental Limitations of the Randomized Controlled Trial Method in Nutritional Research: The Example of Probiotics

Studies on the relation between health and nutrition are often inconclusive. There are concerns about the validity of many research findings, and methods that can deliver high-quality evidence-such as the randomized controlled trial (RCT) method-have been embraced by nutritional researchers. Unfortunately, many nutritional RCTs also yield ambiguous results. It has been argued that RCTs are ill-suited for certain settings, including nutritional research. In this perspective, we investigate whether there are fundamental limitations of the RCT method in nutritional research. To this end, and to limit the scope, we use probiotic studies as an example. We use an epistemological approach and evaluate the presuppositions that underlie the RCT method. Three general presuppositions are identified and discussed. We evaluate whether these presuppositions can be considered true in probiotic RCTs, which appears not always to be the case. This perspective concludes by exploring several alternative study methods that may be considered for future probiotic or nutritional intervention trials.

Overfed but undernourished: recognizing nutritional inadequacies/deficiencies in patients with overweight or obesity

Overweight and obesity are highly prevalent throughout the world and can adversely affect the nutritional status of individuals. Studies have shown that many people with obesity have inadequate intake of iron, calcium, magnesium, zinc, copper, folate and vitamins A and B₁₂, likely as a result of poor diet quality. Nutritional inadequacies or deficiencies may also occur due to altered pharmacokinetics in the individual with obesity and due to interactions in those with overweight or obesity with various pharmaceuticals. However, it has been demonstrated that the adult population in the United States as a whole is deficient in certain micronutrients as a result of the availability and overconsumption of high-calorie, low-nutrient processed foods. Poor nutrition may contribute to the development of certain chronic conditions, such as type 2 diabetes, which is already more prevalent in those with obesity. Clinicians need to be aware of these gaps, particularly in those individuals with obesity who are undergoing bariatric surgery or taking pharmaceutical products long term to facilitate weight loss. Patients with overweight or obesity likely struggle to achieve a balanced diet and may benefit from consultation with a dietitian. Along with providing recommendations for healthy eating and exercise, supplementation with specific micronutrients or multivitamins should be considered for individuals at the highest risk for or with established deficiencies. Further research is needed to understand the factors underlying nutritional inadequacies in individuals with overweight or obesity, as well as the outcomes of treatment strategies employed to address them.

Perspective: Structure-Function Claims on Infant Formula

In the context of a food product label, the term "claim" refers to information that attributes value to the product. The term extends to many different types of information, from product identity, descriptors of intended use, and identification of characteristic properties to the physiologic effects in the body of substances in the food, including the reduction of risk of disease. Food labeling, which includes claims, provides information that consumers want and use to improve their diets. Consumers prefer short statements on the front label claims to longer, more detailed information, including ingredients statements and a nutrition panel. Three types of claims are permitted in the United States. Nutrient content claims describe the level of the nutrient in the food relative to an established daily value, e.g., "Excellent source of choline," and are subject to composition limits for other nutrients, such as total fat, saturated fat, and cholesterol. Health claims describe the relation between a food substance and the risk of disease, e.g., "Adequate calcium and vitamin D throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis." They must undergo a premarket evaluation by the FDA to ensure that there is significant scientific agreement about the relation in question. The third type of claim, structure-function (SF) claims, has recently come under scrutiny, particularly regarding their use on infant formula. Such claims represent a food's effect on the structure or function of the body for maintenance of good health and nutrition. These claims must be truthful and not misleading, but are not subject to premarket approval before use. The purpose of this perspective is to describe the origins and unique niche of SF claims, and to comment on recent proposals to further regulate such claims on infant formula.

Dairy products and bone health: how strong is the scientific evidence?

The relevance of dairy produce for the diminishment of osteoporotic risk is still a matter of scientific debate due to the outcome of a few single observational studies. This review will address the most robust point estimate on the role of dairy products, as reported in systematic reviews and meta-analyses on randomised controlled trials in the case of bone mineralisation or prospective studies in the case of fracture risk. Plain dairy products or those fortified with Ca and/or vitamin D improve total body bone mineral content (BMC) by 45-50 g over 1 year when the daily baseline Ca intake is lower than 750 mg in Caucasians and Chinese girls. In Caucasian and Chinese women, Ca from (fortified) dairy products increases bone mineral density (BMD) by 0·7-1·8 % over 2 years dependent on the site of measurement. Despite the results on BMC, there are currently no studies that have investigated the potential of dairy products to reduce fracture risk in children. In adult Caucasian women, daily intake of 200-250 ml of milk is associated with a reduction in fracture risk of 5 % or higher. In conclusion, the role of dairy products for BMC or BMD has been sufficiently established in Chinese and Caucasian girls and women. In Caucasian women, drinking milk also reduces fracture risk. More research on the role of dairy products within the context of bone health-promoting diets is needed in specific ethnicities, other than Chinese and Caucasians, and in men.

Clinical and Vitamin Response to a Short-Term Multi-Micronutrient Intervention in Brazilian Children and Teens: From Population Data to Interindividual Responses

SCOPE

Micronutrients are in small amounts in foods, act in concert, and require variable amounts of time to see changes in health and risk for disease. These first principles are incorporated into an intervention study designed to develop new experimental strategies for setting target recommendations for food bioactives for populations and individuals.

METHODS AND RESULTS

A 6-week multivitamin/mineral intervention is conducted in 9-13 year olds. Participants (136) are (i) their own control (n-of-1); (ii) monitored for compliance; (iii) measured for 36 circulating vitamin forms, 30 clinical, anthropometric, and food intake parameters at baseline, post intervention, and following a 6-week washout; and (iv) had their ancestry accounted for as modifier of vitamin baseline or response. The same intervention is repeated the following year (135 participants). Most vitamins respond positively and many clinical parameters change in directions consistent with improved metabolic health to the intervention. Baseline levels of any metabolite predict its own response to the intervention. Elastic net penalized regression models are identified, and significantly predict response to intervention on the basis of multiple vitamin/clinical baseline measures.

CONCLUSIONS

The study design, computational methods, and results are a step toward developing recommendations for optimizing vitamin levels and health parameters for individuals.

Ranges of phenotypic flexibility in healthy subjects

BACKGROUND

A key feature of metabolic health is the ability to adapt upon dietary perturbations. A systemic review defined an optimal nutritional challenge test, the "PhenFlex test" (PFT). Recently, it has been shown that the PFT enables the quantification of all relevant metabolic processes involved in maintaining or regaining homeostasis of metabolic health. Furthermore, it was demonstrated that quantification of PFT response was more sensitive as compared to fasting markers in demonstrating reduced phenotypic flexibility in metabolically impaired type 2 diabetes subjects.

METHODS

This study aims to demonstrate that quantification of PFT response can discriminate between different states of health within the healthy range of the population. Therefore, 100 healthy subjects were enrolled (50 males, 50 females) ranging in age (young, middle, old) and body fat percentage (low, medium, high), assuming variation in phenotypic flexibility. Biomarkers were selected to quantify main processes which characterize phenotypic flexibility in response to PFT: flexibility in glucose, lipid, amino acid and vitamin metabolism, and metabolic stress. Individual phenotypic flexibility was visualized using the "health space" by representing the four processes on the health space axes. By quantifying and presenting the study subjects in this space, individual phenotypic flexibility was visualized.

RESULTS

Using the "health space" visualization, differences between groups as well as within groups from the healthy range of the population can be easily and intuitively assessed. The health space showed a different adaptation to the metabolic PhenFlex test in the extremes of the recruited population; persons of young age with low to normal fat percentage had a markedly different position in the health space as compared to persons from old age with normal to high fat percentage.

CONCLUSION

The results of the metabolic PhenFlex test in conjunction with the health space reliably assessed health on an individual basis. This quantification can be used in the future for personalized health quantification and advice.

Vitamin D supplementation and non-alcoholic fatty liver disease: A critical and systematic review of clinical trials

Previous observational studies have found a relationship between vitamin D deficiency and non-alcoholic fatty liver disease (NAFLD). However, this type of study could not show the causal relationship between these two conditions. Therefore, we systematically and critically reviewed the available clinical trials to elucidate such relationship. We searched databases such as Medline, Scopus and Cochrane to identify the clinical trials that assessed the effects of vitamin D supplementation in adults with NAFLD. The outcome variables of interest were indicators of hepatic steatosis, liver enzymes, insulin resistance, inflammation and oxidative stress. A total of 6 studies were included in the qualitative analysis. Only in two studies the grade of hepatic steatosis decreased significantly after vitamin D supplementation. The changes in insulin resistance parameters were reported significant only in one. Of the 3 included studies that measured biomarkers of inflammation and oxidative stress, one revealed a significant decrease in these biomarkers after vitamin D supplementation. Findings from current review study provided new insight into the factors that could affect the therapeutic role of vitamin D in NAFLD. Factors such as gender differences, baseline serum status of vitamin D, co-supplementation with calcium and gene polymorphism should be considered when designing future clinical trials.

The Essentials of a Global Index for Cognitive Function

Cognition is comprised of the faculties: perception, creativity, intuition, and ratiocination. Optimal levels of cognition are needed for independent functioning and balanced living. With an aging population that continues to grow, dietary supplements that tilt the balance towards maintenance of cognition are being marketed for vulnerable populations facing these challenges. Randomized clinical trials provide the causal inference necessary to define the efficacy of emerging nutraceuticals. Cognition testing, in particular, requires a battery of tests that encompass all brain regions involved in cognition so as to provide endpoints necessary for product validation. The lack of well controlled studies for comparison analyses, limited sample sizes, ambiguous dosages, and poor cognitive measures result in data that cannot be compared across studies to determine the efficacy of supplements claiming to enhance cognition. Clinical trials for the nutraceutical industry should consider the multifaceted nature of supplements, where clinical endpoints must be comprehensive while remaining feasible. Combining endpoints of cognition with physiological biomarkers of immunity and metabolism to arrive at a global index for cognitive health may be necessary for claim substantiation in order to fully justify and scientifically validate improvements in cognitive health. The issues and needs of a global index will be discussed here.

Health Claims and Methodological Controversy in Nutrition Science

This article analyzes the debate about data acquisition and assessment in health claims regulation by identifying the underlying controversies on methodological choice. Regulation in the European Union imposes the need for a scientific substantiation of all health claims (claims about a relationship between consumption of certain food ingredients and positive health effects). Randomized controlled trials (RCTs) are the method that generally is considered to provide the highest quality data for decision making in claims regulation because they allow for establishing cause-effect relationships. The latter are demanded in European regulatory practice for authorization of a claim. This requirement has contributed to a debate about the advantages and limitations of the RCT methodology in nutrition research and regulation. Our analysis identifies five types of tensions that underlie the controversy, with respect to evidence, cognitive values, standards of proof, future lines of research, as well as expert judgment. We conclude that there is a direct and mutual interaction between methodological decisions in nutrition science, and different strategies in health claims regulation. The latter have social and public health consequences because not only may they affect the European market for functional foods, as well as concomitant consumption patterns, but also the generation of future regulation-relevant evidence in nutrition.

Optimal nutrition and the ever-changing dietary landscape: a conference report

The field of nutrition has evolved rapidly over the past century. Nutrition scientists and policy makers in the developed world have shifted the focus of their efforts from dealing with diseases of overt nutrient deficiency to a new paradigm aimed at coping with conditions of excess-calories, sedentary lifestyles and stress. Advances in nutrition science, technology and manufacturing have largely eradicated nutrient deficiency diseases, while simultaneously facing the growing challenges of obesity, non-communicable diseases and aging. Nutrition research has gone through a necessary evolution, starting with a reductionist approach, driven by an ambition to understand the mechanisms responsible for the effects of individual nutrients at the cellular and molecular levels. This approach has appropriately expanded in recent years to become more holistic with the aim of understanding the role of nutrition in the broader context of dietary patterns. Ultimately, this approach will culminate in a full understanding of the dietary landscape-a web of interactions between nutritional, dietary, social, behavioral and environmental factors-and how it impacts health maintenance and promotion.

Propelling the paradigm shift from reductionism to systems nutrition

The complex physiology of living organisms represents a challenge for mechanistic understanding of the action of dietary bioactives in the human body and of their possible role in health and disease. Animal, cell, and microbial models have been extensively used to address questions that could not be pursued experimentally in humans, posing an additional level of complexity in translation of the results to healthy and diseased metabolism. The past few decades have witnessed a surge in development of increasingly sensitive molecular techniques and bioinformatic tools for storing, managing, and analyzing increasingly large datasets. Application of such powerful means to molecular nutrition research led to a major leap in study designs and experimental approaches yielding experimental data connecting dietary components to human health. Scientific journals bear major responsibilities in the advancement of science. As primary actors of dissemination to the scientific community, journals can impose rigid criteria for publishing only sound, reliable, and reproducible data. Journal policies are meant to guide potential authors to adopt the most updated standardization guidelines and shared best practices. Such policies evolve in parallel with the evolution of novel approaches and emerging challenges and therefore require constant updating. We highlight in this manuscript the major scientific issues that led to formulating new, updated journal policies for Genes & Nutrition, a journal which targets the growing field of nutritional systems biology interfacing personalized nutrition and preventive medicine, with the ultimate goal of promoting health and preventing or treating disease. We focus here on relevant issues requiring standardization in nutrition research. We also introduce new sections on human genetic variation and nutritional bioinformatics which follow the evolution of nutritional science into the twenty-first century.

Dietary Supplements and Risk of Cause-Specific Death, Cardiovascular Disease, and Cancer: A Systematic Review and Meta-Analysis of Primary Prevention Trials

Our aim was to assess the efficacy of dietary supplements in the primary prevention of cause-specific death, cardiovascular disease (CVD), and cancer by using meta-analytical approaches. Electronic and hand searches were performed until August 2016. Inclusion criteria were as follows: 1) minimum intervention period of 12 mo; 2) primary prevention trials; 3) mean age ≥18 y; 4) interventions included vitamins, fatty acids, minerals, supplements containing combinations of vitamins and minerals, protein, fiber, prebiotics, and probiotics; and 5) primary outcome of all-cause mortality and secondary outcomes of mortality or incidence from CVD or cancer. Pooled effects across studies were estimated by using random-effects meta-analysis. Overall, 49 trials (69 reports) including 287,304 participants met the inclusion criteria. Thirty-two trials were judged as low risk-, 15 trials as moderate risk-, and 2 trials as high risk-of-bias studies. Supplements containing vitamin E (RR: 0.88; 95% CI: 0.80, 0.96) significantly reduced cardiovascular mortality risk, whereas supplements with folic acid reduced the risk of CVD (RR: 0.81; 95% CI: 0.70, 0.94). Vitamins D, C, and K; selenium; zinc; magnesium; and eicosapentaenoic acid showed no significant risk reduction for any of the outcomes. On the contrary, vitamin A was linked to an increased cancer risk (RR: 1.16; 95% CI: 1.00, 1.35). Supplements with β-carotene showed no significant effect; however, in the subgroup with β-carotene given singly, an increased risk of all-cause mortality by 6% (RR: 1.06; 95% CI: 1.02, 1.10) was observed. Taken together, we found insufficient evidence to support the use of dietary supplements in the primary prevention of cause-specific death, incidence of CVD, and incidence of cancer. The application of some supplements generated small beneficial effects; however, the heterogeneous types and doses of supplements limit the generalizability to the overall population.

Efficacy of Multivitamin/mineral Supplementation to Reduce Chronic Disease Risk: A Critical Review of the Evidence from Observational Studies and Randomized Controlled Trials

We reviewed recent scientific evidence regarding the effects of multivitamin/mineral (MVM) supplements on risk of chronic diseases, including cancer, cardiovascular disease, and age-related eye diseases. Data from randomized controlled trials (RCTs) and observational, prospective cohort studies were examined. The majority of scientific studies investigating the use of MVM supplements in chronic disease risk reduction reported no significant effect. However, the largest and longest RCT of MVM supplements conducted to date, the Physicians' Health Study II (PHS II), found a modest and significant reduction in total and epithelial cancer incidence in male physicians, consistent with the Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI.MAX) trial. In addition, PHS II found a modest and significant reduction in the incidence of nuclear cataract, in agreement with several other RCTs and observational, prospective cohort studies. The effects of MVM use on other subtypes of cataract and age-related macular degeneration remain unclear. Neither RCTs nor prospective cohort studies are without their limitations. The placebo-controlled trial design of RCTs may be inadequate for nutrient interventions, and residual confounding, measurement error, and the possibility of reverse causality are inherent to any observational study. National surveys show that micronutrient inadequacies are widespread in the US and that dietary supplements, of which MVMs are the most common type, help fulfill micronutrient requirements in adults and children.

The Healthy Core Metabolism: A New Paradigm for Primary Preventive Nutrition

Research in preventive nutrition aims at elucidating mechanism by which our diet helps us to remain in good health through optimal physiological functions. However, despite decades of accumulated data in human nutrition and regular subsequent nutritional recommendations, obesity and type 2 diabetes epidemics continue to progress worldwide each year leading to a regular decrease of the Healthy Life Years, notably in Western countries. Such a paradox may be explained by the Nutrition Transition, the extreme application of the reductionist paradigm in nutrition research, the lack of nutritional education and a too strong focus on curative nutrition in at risk/ill subjects. In this position paper, we hypothesized that researchers should focus more on healthy subjects, from birth until maturity. Rather than exploring what differentiates healthy and at risk/ill subjects, we propose to thoroughly study what characterizes a healthy state and its underlying metabolism. We define it as the Healthy Core Metabolism which remains stable whatever energy inputs (diets) and outputs (exercise), genetic background and external/internal stress, e.g., temporary illnesses. As a basis for Healthy Core Metabolism investigation, we observed that main physiological and ubiquitous functions of human organism, i.e., the neuro-vasculo-sarco-osteoporotic system, tend to follow a concave curve with common phases of growth, optimum, and decline. Finally, we hypothesized that true primary preventive nutrition should focus on the growth phase to reach the maximum capital of a given physiological function so that - whatever the further decline -, Healthy Life Years may approach or coincide with theoretical Life Expectancy.

Dairy in a sustainable diet: a question of balance

The demand for dairy products is growing rapidly, especially in emerging markets. Dairy products are nutrient rich and, therefore, an important food group for ensuring nutrient security in the future. In many countries, dairy contributes significantly to nutrient intake. Meta-analyses have shown that consumption of dairy may reduce the risk of chronic diseases and thereby lower healthcare costs. Milk production and processing contribute to greenhouse gas emissions, estimated at 2.7% (cradle-to-retail) of the world's total. Evaluating the position of dairy in the diet should take into account the impact of both nutritional and environmental factors. Local conditions are also important; in many parts of the world, the cow is an efficient converter of human-inedible resources into nutrient-dense food. Increased productivity of cows is a decisive factor in realizing sufficient milk production with optimal resource efficiency and minimal greenhouse gas emission. Models that optimize total diets, rather than individual food products, for their nutritional and environmental impact are the preferred approach for developing realistic alternative consumption strategies.

Nutrition and health technology assessment: when two worlds meet

There is a growing recognition that nutrition may have a positive impact on public health and that it may reduce medical expenditures. Yet, such claims need to be substantiated by evidence. This evidence could be delivered by health technology assessment (HTA), which can be thought of as the evaluation of technologies for clinical effectiveness, cost-effectiveness, and ethical, legal, and social impacts. The application of HTA to the field of “nutrition interventions” is recent. So far, HTA and nutrition have represented two worlds far apart in many respects. This contribution, roughly, addresses the following issues: is there a need for HTAs in the field of nutrition, what would such HTAs look like, and how can the results coming from these HTAs optimally aid policy making?

In essence, HTAs of nutrition have much of the same basic principles and structure as HTAs of “classical” health care treatments. Nevertheless, there are challenges to rigorous HTAs of nutrition interventions, for various reasons. To mention a few: the evidence base for nutrition interventions is less well developed than that for many health care treatments. Furthermore, it is a matter of debate which outcome measures should be used in HTAs of nutrition. For example, one may argue that nutrition not only has health effects, but also effects that are not captured by traditional health-related quality of life measures (e.g., the pleasure of eating, effects relating to ease of use, or effects on well-being).

HTAs in the field of nutrition may deliver information valuable to a wide range of stakeholders, including consumers/patients, health professionals, hospital administrators, insurers, and decision makers. The results of HTAs are typically used in making treatment guidelines, in informing decisions about reimbursement or about public health campaigns, etc. Yet, it is uncertain how the results of HTAs of nutrition can be used optimally. For example, would it be possible to summarize the results of a HTA in a single ratio (such as costs per quality-adjusted life-year gained) and then to either approve or reject the intervention based on this ratio, compared to a certain threshold? Apart from that, in the field of nutrition, it is typically not about reimbursement of a technology. Related to this, it is important that the message from HTAs of nutrition is brought to a range of stakeholders including the general population and that these HTAs are tailored to the decision-making context.

To conclude, a growing need is felt for HTA-type evaluations of nutrition, which are sparse these days. Little thought has been given to developing an optimal methodology for HTAs of nutrition and to how its results should be integrated into policy making. Further work in these areas would stimulate the development of nutrition interventions that yield a gain in societal welfare. To achieve this, the two worlds of HTA and nutrition need to be brought together.

Stakeholders' perception of the nutrition and health claim regulation

In 2007, the Nutrition and Health Claim Regulation (NHCR) entered into force, which required scientific substantiation of health claims. In the field of antioxidants, most proposed claims were negatively assessed by the European Food Safety Authority (EFSA). This study reviews the perception of the NHCR of 14 Dutch stakeholders to unravel the grounds for disproving the putative health claims. Most claims are shown to be refused based on the quality of scientific substantiation, due to usage of scientific methods on which no consensus has been reached and the differences in expectations and requirements. Three themes exemplify the need for improvement in applying the NHCR: (i) enforcement; (ii) methodology; and (iii) perceived impact of the NHCR. With highly diverging perceptions of stakeholders, the current effectiveness of the NHCR can be questioned. The views of different stakeholders on these themes help to focus the discussion on the NCHR in capturing health effects.

Biochemical markers for assessment of calcium economy and bone metabolism: application in clinical trials from pharmaceutical agents to nutritional products

Nutrition plays an important role in osteoporosis prevention and treatment. Substantial progress in both laboratory analyses and clinical use of biochemical markers has modified the strategy of anti-osteoporotic drug development. The present review examines the use of biochemical markers in clinical research aimed at characterising the influence of foods or nutrients on bone metabolism. The two types of markers are: (i) specific hormonal factors related to bone; and (ii) bone turnover markers (BTM) that reflect bone cell metabolism. Of the former, vitamin D metabolites, parathyroid hormone, and insulin-like growth factor-I indicate responses to variations in the supply of bone-related nutrients, such as vitamin D, Ca, inorganic phosphate and protein. Thus modification in bone remodelling, the key process upon which both pharmaceutical agents and nutrients exert their anti-catabolic or anabolic actions, is revealed. Circulating BTM reflect either osteoclastic resorption or osteoblastic formation. Intervention with pharmacological agents showed that early changes in BTM predicted bone loss and subsequent osteoporotic fracture risk. New trials have documented the influence of nutrition on bone-tropic hormonal factors and BTM in adults, including situations of body-weight change, such as anorexia nervosa, and weight loss by obese subjects. In osteoporosis-prevention studies involving dietary manipulation, randomised cross-over trials are best suited to evaluate influences on bone metabolism, and insight into effects on bone metabolism may be gained within a relatively short time when biochemical markers are monitored.

Developing suitable methods of nutritional status assessment: a continuous challenge

Reliable information about the nutritional status is essential to identify potential critical nutrients and the population groups at risk of deficiency, as well as to develop effective public health policies to counteract unfavorable nutrition patterns that contribute to morbidity and mortality. In this review, the important role of biomarkers in the assessment of nutritional status is outlined, major strengths and limitations of established and new biomarkers are described, and important criteria for biomarker selection and development are discussed. Indeed, biomarkers offer a more objective assessment tool than pure dietary approaches that suffer from inadequate data reporting in particular, although biomarkers are often only measured in subsamples because of the higher costs and proband burden they entail. However, biomarkers are subject to individual variability and influences from other factors besides the nutrient of interest. Rapid turnover or tight control of nutrient concentrations in blood (homeostasis) limits their sensitivity as biomarkers, as in the case of many trace elements. The existence of different forms of a micronutrient in the body adds additional complexity. Functional biomarkers, such as enzyme activities, mirror long-term status better but are subject to confounding factors, and some are influenced by several micronutrients, not specific for only 1, so using a combination of biomarkers is advisable. Additionally, the applicability of a biomarker also depends on the existence of adequate reference values and cutoff points for the target population. Therefore, a careful selection is warranted, especially when biomarkers are to be used in larger samples.

Addressing nutritional gaps with multivitamin and mineral supplements

A balanced and varied diet is the best source of essential vitamins and minerals; however, nutrient deficiencies occur, including in populations with bountiful food supplies and the means to procure nutrient-rich foods. For example, the typical American diet bears little resemblance to what experts recommend for fruit, vegetables, and whole grains, which serve as important sources of an array of vitamins and minerals. With time, deficiencies in one or more micronutrients may lead to serious health issues. A common reason people take multivitamin and mineral (MVM) supplements is to maintain or improve health, but research examining the effectiveness of MVMs in the prevention of certain chronic conditions is ongoing. In addition to the utility of MVMs for filling in relatively small but critical nutritional gaps, which may help prevent conditions such as anemia, neural tube defects, and osteoporosis, some evidence supports possible benefits of MVM supplementation with regard to cancer prevention (particularly in men) and prevention or delay of cataract, as well as some aspects of cognitive performance. Unlike some single-vitamin supplements, MVM supplements are generally well tolerated and do not appear to increase the risk of mortality, cerebrovascular disease, or heart failure. The potential benefits of MVM supplements likely outweigh any risk in the general population and may be particularly beneficial for older people.

Does vitamin D sufficiency equate to a single serum 25-hydroxyvitamin D level or are different levels required for non-skeletal diseases?

Objective: Clarify the concept of vitamin D sufficiency, the relationship between efficacy and vitamin D status and the role of Vitamin D supplementation in the management of non-skeletal diseases. We outline reasons for anticipating different serum vitamin D levels are required for different diseases. Method: Review the literature for evidence of efficacy of supplementation and minimum effective 25-hydroxyvitamin D (25-OHD) levels in non-skeletal disease. Results: Evidence of efficacy of vitamin supplementation is graded according to levels of evidence. Minimum effective serum 25-OHD levels are lower for skeletal disease, e.g., rickets (25 nmol/L), osteoporosis and fractures (50 nmol/L), than for premature mortality (75 nmol/L) or non-skeletal diseases, e.g., depression (75 nmol/L), diabetes and cardiovascular disease (80 nmol/L), falls and respiratory infections (95 nmol/L) and cancer (100 nmol/L). Conclusions: Evidence for the efficacy of vitamin D supplementation at serum 25-OHD levels ranging from 25 to 100 nmol/L has been obtained from trials with vitamin D interventions that change vitamin D status by increasing serum 25-OHD to a level consistent with sufficiency for that disease. This evidence supports the hypothesis that just as vitamin D metabolism is tissue dependent, so the serum levels of 25-OHD signifying deficiency or sufficiency are disease dependent.

Ten misconceptions about antioxidants

Oxidative damage is a common cellular event involved in numerous diseases and drug toxicities. Antioxidants prevent or delay oxidative damage, and therefore there has been extensive research into the discovery of natural and newly designed antioxidants. Initial excitement regarding the potential health benefits of antioxidants has diminished. Currently, it is even claimed that antioxidants increase mortality. The antioxidant pendulum appears to swing from healthy to toxic and from general panacea to insignificant ingredient. Owing to the polarity of views towards antioxidants, nutritional recommendation ranges from advice to increase antioxidant status in plasma to the notion that it is a useless measurement. Such views, lacking sufficient scientific support, lead to misconceptions, which in our opinion hinder the rational use of food supplements and impedes the design and development of new antioxidant drugs. As a result, good opportunities might easily be missed.

Why critically ill patients are protein deprived

Critical illness dramatically increases muscle proteolysis and more than doubles the dietary protein requirement. Yet surprisingly, most critically ill patients receive less than half the recommended amount of protein during their stay in a modern intensive care unit. What could explain the wide gap between the recommendations in clinical care guidelines and actual clinical practice? We suggest that an important aspect of the problem is the failure of guidelines to explain the pathophysiology of protein-energy malnutrition and the ways critical illness modifies protein metabolism. The difficulty created by the lack of a framework for reasoning about appropriate protein provision in critical illness is compounded by the many ambiguous and often contradictory ways the word malnutrition is used in the critical care literature. Failing to elucidate these matters, the recommendations for protein provision in the guidelines are incoherent, unconvincing, and easy to ignore.

What is vitamin D insufficiency? And does it matter?

The term nutrient "insufficiency," as commonly used, refers to a nutritional status intermediate between classical, severe deficiency, and full normal. As both "deficiency" and "insufficiency" are causes of dysfunction and disease, there is no biological basis for a distinction between them. What is important to note is that, in the case of vitamin D, the preponderance of the evidence indicates that there is real, preventable disease in the range of vitamin D status values now labeled "insufficient."

Dairy foods and osteoporosis: an example of assessing the health-economic impact of food products

Osteoporosis has become a major health concern, carrying a substantial burden in terms of health outcomes and costs. We constructed a model to quantify the potential effect of an additional intake of calcium from dairy foods on the risk of osteoporotic fracture, taking a health economics perspective.

INTRODUCTION

This study seeks, first, to estimate the impact of an increased dairy consumption on reducing the burden of osteoporosis in terms of health outcomes and costs, and, second, to contribute to a generic methodology for assessing the health-economic outcomes of food products.

METHODS

We constructed a model that generated the number of hip fractures that potentially can be prevented with dairy foods intakes, and then calculated costs avoided, considering the healthcare costs of hip fractures and the costs of additional dairy foods, as well as the number of disability-adjusted life years (DALYs) lost due to hip fractures associated with low nutritional calcium intake. Separate analyses were done for The Netherlands, France, and Sweden, three countries with different levels of dairy products consumption.

RESULTS

The number of hip fractures that may potentially be prevented each year with additional dairy products was highest in France (2,023), followed by Sweden (455) and The Netherlands (132). The yearly number of DALYs lost was 6,263 for France, 1,246 for Sweden, and 374 for The Netherlands. The corresponding total costs that might potentially be avoided are about 129 million, 34 million, and 6 million Euros, in these countries, respectively.

CONCLUSIONS

This study quantified the potential nutrition economic impact of increased dairy consumption on osteoporotic fractures, building connections between the fields of nutrition and health economics. Future research should further collect longitudinal population data for documenting the net benefits of increasing dairy consumption on bone health and on the related utilization of healthcare resources.

Why randomized controlled trials of calcium and vitamin D sometimes fail

The importance of nutrients for promotion of health and prevention of disease has long been recognized. Nonetheless, scientists are still trying to delineate the optimal intakes of various nutrients and their potential benefits for different populations. To that end, evidence-based medicine (EBM) has been applied to the study of nutrition. EBM methods basically call for the use of randomized controlled trials (RCTs) to establish causal connection between the intervention and any particular endpoint. This paper focuses on problems that arise in the use of RCTS to establish a causal link between nutrients and various clinical endpoints. While many RCTS of calcium and vitamin D have been positive, many others have been null. In this paper, we discuss the reasons why effective nutrient agents may be found to be ineffective in particular studies, giving examples of such null results, and focusing on the nearly universal failure to consider biological criteria in designing RCTs. Our purpose is (1) to inform future study design so as to ensure that relevant biological facts are considered and (2) to aid in the interpretation of the abundant, but often inconsistent literature on this topic.

Pleiotropic-acting nutrients require integrative investigational approaches: the example of flavonoids

Assessment of the health effects of dietary interventions in humans poses a particular challenge to nutritional and clinical scientists. In contrast to drugs possessing a well-defined molecular mechanism of action, food-derived components act in subtle and pleiotropic ways by nature. Moreover, dietary compounds are mainly not intended to cure a disease but to prevent or beneficially affect situations when the physiology gets slightly out of homeostasis. By the example of a recent clinical pilot study, this paper illustrates an endeavor to find new strategies for the detection of health effects of flavonoids in the human vasculature. Integration of a meticulously selected cluster of relevant biomarkers eventually enabled the beneficial vascular health effects of flavonoids to be revealed. A critical appraisal of this approach for the future is provided.

The effects of dietary intervention on HIV dyslipidaemia: a systematic review and meta-analysis

BACKGROUND

Efficacy of dietary intervention for treatment and prevention of HIV-related lipid disturbances has not been well established.

METHODS

We conducted a systematic search of electronic databases supplemented with manual searches and conference abstracts, without language restriction. All randomised controlled trials (RCTs) with blood lipid outcomes, involving dietary intervention or supplementation for the treatment or prevention of adult HIV dyslipidaemia, versus no or other intervention were included. Two authors using predefined data fields, including study quality indicators, extracted data independently.

RESULTS

Eighteen studies (n = 873) met our inclusion criteria. Seven RCTs for omega-3 supplementation (n = 372), and four RCTs for dietary intervention (n = 201) were meta-analysed using random-effects models. Mild statistical heterogeneity was observed. Dietary intervention reduced triglyceride levels by -0·46 mmol/l (95%CI: -0·85 to -0·07 mmol/l) compared to control. Omega-3 supplementation reduced triglyceride levels by -1.12 mmol/l, (95%CI: -1·57 to -0·67 mmol/l) and total cholesterol, -0·36 mmol/l (95%CI: -0·67 to -0·05 mmol/l) compared to placebo/control.

CONCLUSIONS

Both omega-3 supplementation and dietary intervention reduced triglyceride level, with the latter possibly to a smaller extent. While dietary interventions are beneficial, more stringent dietary approaches may be necessary to fully address lipid disturbances in HIV patients.

TRIAL REGISTRATION

PROSPERO 2011:CRD42011001329.