Nutritional genomics in practice: where do we begin?

"Right diet for the right person": a focus group study of nutritionist-dietitians' perspectives on nutritional genomics and gene-based nutrition advice

Advances in nutritional genomics are intended to revolutionize nutrition practice. A basic understanding of nutritional genomics among nutritionist-dietitians is critical for such advancements to occur. As a precedent to the development and integration of gene-based nutrition advice, this study aimed to assess hospital-based nutritionist-dietitians' perceptions of nutritional genomics. A total of ten focus group discussions (FGDs) with sixty-one registered nutritionist-dietitians (RNDs) from hospitals in the National Capital Region (NCR), Philippines, were conducted from October to November 2019. Data were collected using a pretested semistructured discussion guide, and thematic analysis was subsequently performed. Diverging perceptions about nutritional genomics were noted among the FGD participants. Five themes emerged relating to the enablers and barriers of gene-based nutrition advice: training and capacity building, the extent of information to be disclosed, cost, ethical considerations, and government support. Themes related to the desired features of the gene-based nutrition advice included being consent-driven, cost-effective, technology-oriented, and guided by standards. The results of this study suggest that training and continued learning will equip RNDs to provide nutrition advice based on genetic information. However, other factors, such as cost and ethical considerations, are critical dimensions that need to be acknowledged and addressed before integrating gene-based advice into nutrition practice.

Genes Related to Fat Metabolism in Pigs and Intramuscular Fat Content of Pork: A Focus on Nutrigenetics and Nutrigenomics

Simple Summary

The intramuscular fat (IMF) or marbling is an essential pork sensory quality that influences the preference of the consumers and premiums for pork. IMF is the streak of visible fat intermixed with the lean within a muscle fibre and determines sensorial qualities of pork such as flavour, tenderness and juiciness. Fat metabolism and IMF development are controlled by dietary nutrients, genes, and their metabolic pathways in the pig. Nutrigenetics explains how the genetic make-up of an individual pig influences the pig’s response to dietary nutrient intake. Differently, nutrigenomics is the analysis of how the entire genome of an individual pig is affected by dietary nutrient intake. The knowledge of nutrigenetics and nutrigenomics, when harmonized, is a powerful tool in estimating nutrient requirements for swine and programming dietary nutrient supply according to an individual pig’s genetic make-up. The current paper aimed to highlight the roles of nutrigenetics and nutrigenomics in elucidating the underlying mechanisms of fat metabolism and IMF deposition in pigs. This knowledge is essential in redefining nutritional intervention for swine production and the improvement of some economically important traits such as growth performance, backfat thickness, IMF accretion, disease resistance etc., in animals.

Abstract

Fat metabolism and intramuscular fat (IMF) are qualitative traits in pigs whose development are influenced by several genes and metabolic pathways. Nutrigenetics and nutrigenomics offer prospects in estimating nutrients required by a pig. Application of these emerging fields in nutritional science provides an opportunity for matching nutrients based on the genetic make-up of the pig for trait improvements. Today, integration of high throughput “omics” technologies into nutritional genomic research has revealed many quantitative trait loci (QTLs) and single nucleotide polymorphisms (SNPs) for the mutation(s) of key genes directly or indirectly involved in fat metabolism and IMF deposition in pigs. Nutrient–gene interaction and the underlying molecular mechanisms involved in fatty acid synthesis and marbling in pigs is difficult to unravel. While existing knowledge on QTLs and SNPs of genes related to fat metabolism and IMF development is yet to be harmonized, the scientific explanations behind the nature of the existing correlation between the nutrients, the genes and the environment remain unclear, being inconclusive or lacking precision. This paper aimed to: (1) discuss nutrigenetics, nutrigenomics and epigenetic mechanisms controlling fat metabolism and IMF accretion in pigs; (2) highlight the potentials of these concepts in pig nutritional programming and research.

Nutrigenetics-personalized nutrition in obesity and cardiovascular diseases

Epidemiological data support the view that both obesity and cardiovascular diseases (CVD) account for a high proportion of total morbidity and mortality in adults throughout the world. Obesity and CVD have complex interplay mechanisms of genetic and environmental factors, including diet. Nutrition is an environmental factor and it has a predominant and recognizable role in health management and in the prevention of obesity and obesity-related diseases, including CVD. However, there is a marked variation in CVD in patients with obesity and the same dietary pattern. The different genetic polymorphisms could explain this variation, which leads to the emergence of the concept of nutrigenetics. Nutritional genomics or nutrigenetics is the science that studies and characterizes gene variants associated with differential response to specific nutrients and relating this variation to various diseases, such as CVD related to obesity. Thus, the personalized nutrition recommendations, based on the knowledge of an individual's genetic background, might improve the outcomes of a specific dietary intervention and represent a new dietary approach to improve health, reducing obesity and CVD. Given these premises, it is intuitive to suppose that the elucidation of diet and gene interactions could support more specific and effective dietary interventions in both obesity and CVD prevention through personalized nutrition based on nutrigenetics. This review aims to briefly summarize the role of the most important genes associated with obesity and CVD and to clarify the knowledge about the relation between nutrition and gene expression and the role of the main nutrition-related genes in obesity and CVD.

Epigenetic Mechanisms in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a brain-gut axis disorder characterized by abdominal pain and altered bowel habits. IBS is a multifactorial, stress-sensitive disorder with evidence for familial clustering attributed to genetic or shared environmental factors. However, there are weak genetic associations reported with IBS and a lack of evidence to suggest that major genetic factor(s) contribute to IBS pathophysiology. Studies on animal models of stress, including early life stress, suggest a role for environmental factors, specifically, stress associated with dysregulation of corticotropin releasing factor and hypothalamus-pituitary-adrenal (HPA) axis pathways in the pathophysiology of IBS. Recent evidence suggests that epigenetic mechanisms, which constitute molecular changes not driven by a change in gene sequence, can mediate environmental effects on central and peripheral function. Epigenetic alterations including DNA methylation changes, histone modifications, and differential expression of non-coding RNAs (microRNA [miRNA] and long non-coding RNA) have been associated with several diseases. The objective of this review is to elucidate the molecular factors in the pathophysiology of IBS with an emphasis on epigenetic mechanisms. Emerging evidence for epigenetic changes in IBS includes changes in DNA methylation in animal models of IBS and patients with IBS, and various miRNAs that have been associated with IBS and endophenotypes, such as increased visceral sensitivity and intestinal permeability. DNA methylation, in particular, is an emerging field in the realm of complex diseases and a promising mechanism which can provide important insights into IBS pathogenesis and identify potential targets for treatment.

The State of Nutrigenomic Education in Poland

BACKGROUND

In Poland, 45 higher education institutions offer degrees in dietetics. However, only 20 of these offer nutrigenomics or nutrigenetics courses.

OBJECTIVES

The purpose of this study was to assess the current state of nutri-genomic education in Poland and to evaluate the level of nutrigenomic knowledge held by dieticians.

METHODS

A cross-sectional survey was performed to examine the self-reported attitudes of 193 dietetics students and dietetics professionals who graduated from 33 Polish higher-level institutions.

RESULTS

The great majority of respondents were familiar with nutrigenomics and had a positive attitude to it, and this attitude was independent of whether they participated in nutrigenomics courses. Sixty-six percent of the respondents had received training in nutrigenomics, but nutrigenomic education did not meet the expectations of 57% of dieticians. Dieticians possess low levels of self-reported knowledge of nutrigenomics, and only about 15% of respondents know how to effectively communicate information on genetic risk to patients and understand the effect of nutrients on molecular mechanisms. Despite this lack of knowledge, 59% of respondents had a positive attitude to nutri-genomics, and 63% of them had a great interest in broadening their knowledge. Subjects who had participated in nutrigenomics courses exhibited a better understanding of several areas of nutrigenomics. They were especially interested in practical aspects of nutrigenomics, such as the essence of personalized diets and the practical application of nutrigenomics.

CONCLUSIONS

In conclusion, Polish dieticians have a positive attitude to nutrigenomics but do not perceive themselves as well educated in this field, which is partly due to systemic problems. The study shows the need for improvements in nutrigenomic education in Poland.

Translation of Nutritional Genomics into Nutrition Practice: The Next Step

Genetics is an important piece of every individual health puzzle. The completion of the Human Genome Project sequence has deeply changed the research of life sciences including nutrition. The analysis of the genome is already part of clinical care in oncology, pharmacology, infectious disease and, rare and undiagnosed diseases. The implications of genetic variations in shaping individual nutritional requirements have been recognised and conclusively proven, yet routine use of genetic information in nutrition and dietetics practice is still far from being implemented. This article sets out the path that needs to be taken to build a framework to translate gene–nutrient interaction studies into best-practice guidelines, providing tools that health professionals can use to understand whether genetic variation affects nutritional requirements in their daily clinical practice.

Probiotics: The scientific evidence in the context of inflammatory bowel disease

Inflammatory bowel disease (IBD) generally comprises Crohn's disease (CD) and ulcerative colitis (UC), and their main characteristic is the intestinal mucosa inflammation. Although its origin is not yet fully known, there is growing evidence related to genetics, intestinal microbiota composition, and the immune system factors such as precursors for the initiation and progression of intestinal conditions. The use of certain probiotic microorganisms has been touted as a possible and promising therapeutic approach in reducing the risk of inflammatory bowel disease, specifically ulcerative colitis. Several mechanisms have been proposed to explain the benefits of probiotics, indicating that some bacterial strains are able to positively modulate the intestinal microbiota and the immune system, and to produce metabolites with anti-inflammatory properties. The aim of this paper is to bring together the various results and information, based on scientific evidence, that are related to probiotics and inflammatory bowel disease, emphasizing the possible mechanisms involved in this action.

Fructooligosaccharide intake promotes epigenetic changes in the intestinal mucosa in growing and ageing rats

PURPOSE

The aim of this study was to investigate the relationship between fructooligosaccharide (FOS) intake at different life stages of Wistar rats and its stimulatory effects on intestinal parameters.

METHODS

Recently weaned and ageing female rats were divided into growing and ageing treatments, which were fed diets that partially replaced sucrose with FOS for 12 weeks.

RESULTS

Dietary FOS intake induced a significant increase in the numbers of Bifidobacterium and Lactobacillus in growing rats. FOS intake was associated with increased butyric acid levels and a reduced pH of the caecal contents at both ages. Differential gene expression patterns were observed by microarray analysis of growing and ageing animals fed the FOS diet. A total of 133 genes showed detectable changes in expression in the growing rats, while there were only 19 gene expression changes in ageing rats fed with FOS.

CONCLUSION

These results suggest that dietary FOS intake may be beneficial for some parameters of intestinal health in growing rats.

The role of nutrition related genes and nutrigenetics in understanding the pathogenesis of cancer

Nutrition has a predominant and recognizable role in health management. Nutrigenetics is the science that identifies and characterizes gene variants associated with differential response to nutrients and relating this variation to variable disease states especially cancer. This arises from the epidemiological fact that cancer accounts for a high proportion of total morbidity and mortality in adults throughout the world. There is much evidence to support that genetic factors play a key role in the development of cancer; these genetic factors such as DNA instability and gene alterations are affected by nutrition. Nutrition may also lead to aberrant DNA methylation, which in turn contributes to carcinogenesis. The aim of this work is to clarify the basic knowledge about the vital role of nutrition-related genes in various disease states, especially cancer, and to identify nutrigenetics as a new concept that could highlight the relation between nutrition and gene expression. This may help to understand the mechanism and pathogenesis of cancer. The cause of cancer is a complex interplay mechanism of genetic and environmental factors. Dietary nutrient intake is an essential environmental factor and there is a marked variation in cancer development with the same dietary intake between individuals. This could be explained by the variation in their genetic polymorphisms, which leads to emergence of the concept of nutrigenomics and nutrigenetics.

Potential antioxidant response to coffee - A matter of genotype?

In a human intervention study, coffee combining natural green coffee bean constituents and dark roast products was identified as a genotype-dependent inducer of the Nrf2/ARE pathway, significantly affecting Nrf2 gene expression and downstream GST1A1 and UGT1A1 gene transcription. The observed transcriptional changes correlated with the presence of specific Nrf2 genotypes suggesting their influence on both Nrf2 and subsequent ARE-dependent GST1A1 and UGT1A1 transcription. While the presence of the − 653 SNP seems to be advantageous, resulting in higher Nrf2, GST1A1 and UGT1A1 gene transcription following coffee consumption, in contrast, the presence of the − 651 SNP significantly down-regulated the response to the study coffee. Furthermore, the presence of the B/B genotype in GST1A1 along with the frequency of the [TA]_6/6 and [TA]_7/7 polymorphisms in UGT1A1 appeared to significantly increase sensitivity toward coffee-induced gene transcription. This data suggests that when examining the role of the Nrf2/ARE pathway in the regulation of antioxidative and chemopreventive phase II efficacy, individual genotypes should be included when considering the potency of bioactive food/food constituents and their therapeutic potential.

The application of genetics and nutritional genomics in practice: an international survey of knowledge, involvement and confidence among dietitians in the US, Australia and the UK

As a result of expanding scientific understanding of the interplay between genetics and dietary risk factors, those involved in nutritional management need to understand genetics and nutritional genomics in order to inform management of individuals and groups. The aim of this study was to measure and determine factors affecting dietitians' knowledge, involvement and confidence in genetics and nutritional genomics across the US, Australia and the UK. A cross-sectional study was undertaken using an online questionnaire that measured knowledge and current involvement and confidence in genetics and nutritional genomics. The questionnaire was distributed to dietitians in the US, Australia and the UK using email lists from the relevant professional associations. Data were collected from 1,844 dietitians who had practiced in the previous 6 months. The main outcomes were knowledge of genetics and nutritional genomics and involvement and confidence in undertaking clinical and educational activities related to genetics and nutritional genomics. Mean scores for knowledge, involvement and confidence were calculated. Analysis of variance and χ (2) analysis were used to compare scores and frequencies. Multivariate linear regression was used to determine predictors of high scores. The results demonstrated significant differences in involvement (p < 0.001) and confidence (p < 0.001) but not knowledge scores (p = 0.119) between countries. Overall, dietitians reported low levels of knowledge (mean knowledge score 56.3 %), involvement (mean number of activities undertaken 20.0-22.7 %) and confidence (mean confidence score 25.8-29.7 %). Significant relationships between confidence, involvement and knowledge were observed. Variables relating to education, experience, sector of employment and attitudes were also significantly associated with knowledge, involvement and confidence. Dietitians' knowledge, involvement and confidence relating to genetics and nutritional genomics remain low and further investigation into factors contributing to this is required.

Quantifying diet for nutrigenomic studies

The field of nutrigenomics shows tremendous promise for improved understanding of the effects of dietary intake on health. The knowledge that metabolic pathways may be altered in individuals with genetic variants in the presence of certain dietary exposures offers great potential for personalized nutrition advice. However, although considerable resources have gone into improving technology for measurement of the genome and biological systems, dietary intake assessment remains inadequate. Each of the methods currently used has limitations that may be exaggerated in the context of gene × nutrient interaction in large multiethnic studies. Because of the specificity of most gene × nutrient interactions, valid data are needed for nutrient intakes at the individual level. Most statistical adjustment efforts are designed to improve estimates of nutrient intake distributions in populations and are unlikely to solve this problem. An improved method of direct measurement of individual usual dietary intake that is unbiased across populations is urgently needed.

Canadian health care professionals' knowledge, attitudes and perceptions of nutritional genomics

Nutritional genomics has reached the public through applications of the Human Genome Project offered direct to consumers (DTC). The ability to pursue nutrigenetic testing without the involvement of a health care professional has received considerable attention from academic and policy commentators. To better understand the knowledge and attitudes of Canadian health care professionals regarding nutritional genomics and nutrigenetic testing, qualitative research in the form of focus group discussions was undertaken. Four key themes emerged: (1) concerns over DTC testing; (2) lack of health care professional competency; (3) genetic scepticism and inevitability; (4) expectation of regulation. Together, they indicate that health care professionals have little knowledge about nutritional genomics and hold contradictory attitudes towards genomics in general, and to nutritional genomics in particular. Respondents argue in favour of a delivery model where health care professionals act as intermediaries. They are also aware of their lack of competency to provide such services. To ensure greater public protection, respondents cite the importance of more stringent regulatory oversight of DTC genetic testing. Whether such an approach is necessary to address the various ethical and social issues raised by nutrigenetic testing remains an open debate.

Nutrigenomics approaches to functional foods

By definition, functional foods benefit human health beyond the effect of nutrients alone. However, few are accompanied by convincing health claims, partly because human responses are variable. Nutritional biochemistry explains why polymorphisms in genes for the absorption, circulation, or metabolism of essential nutrients, such as n-3 polyunsaturated fatty acids, would affect the efficacy of that nutrient. However, functional foods often incorporate bioactive compounds, such as epigallocatechin-3-gallate, without considering the interaction with genetic polymorphisms. For either example there will be individuals whose genotype precludes their deriving significant benefit from an increased intake of such foods, and a small segment of the population that may be disadvantaged. Large-scale, whole-genome association studies are providing unprecedented understanding of the genetic basis of health and chronic disease. This rapidly evolving genomic science often fails to consider the interaction with environmental exposure like diet. It is important that the dietetics profession ensures rigorous nutrition science alongside genetic evaluation as part of future study design to derive informed information on gene-diet interactions that may enable clients to rationally select foods leading to optimal health or reduced risk of chronic disease.

Nutritional genomics and dietetic professional practice

Nutrigenomics is concerned with the role of nutrients in gene expression, and nutrigenetics is the study of how genetic variants or polymorphisms (mutations) can affect responses to nutrients; nutritional genomics is the umbrella term. Nutritional genomics can be expected to revolutionize the way dietitians and other health professionals identify people with chronic diseases and treat those diseases. Understanding the science of nutritional genomics is important to dietitians and other health professionals because major scientific advancements such as this usually have a significant impact on ethics, policy, and practice. Blood lipid profiles are one area in which nutritional genomics has quickly advanced knowledge. New knowledge is available on blood lipid profiles and associated conditions, such as obesity and type 2 diabetes. New technology has also had an impact on policy and practice issues, and ethics is an important issue to consider.

Understanding the nutrigenomic definitions and concepts at the food-genome junction

The marked differences in individual response to dietary factors have led to major controversies in nutrition and puzzled nutrition scientists over the last century. The emerging field of nutrigenomics helps us to understand the basis for some of these differences and also promises us the ability to tailor diet based on individual genetic makeup. Great advances in Human Genome Project, documentation of single nucleotide polymorphisms (SNPs) in candidate genes and their association with metabolic imbalances have gradually added new tests to the nutrigenomic panel. Studies based on ethnopharmacology and phytotherapy concepts showed that nutrients and botanicals can interact with the genome causing marked changes in gene expression. This has led to the commercial development of nutraceuticals and functional foods that can modify negative health effects of individual genetic profile bringing the field to the "food/genome" junction. Despite the promise of nutrigenomics to personalize diet, there is skepticism whether it can truly bring about meaningful modification of the risk factors connected to chronic diseases, due to the lack of large scale nutrition intervention studies. Several intervention studies currently underway in the United States and abroad (Israel, Spain, and France) will further help validate nutrigenomic concepts. France has already introduced a National Nutrition and Health Program to assess nutritional status and risk of major metabolic diseases. As the field(s) related to nutritional genomics advance in their scope, it is essential that: (a) strict guidelines be followed in the nomenclature and definition of the subdisciplines; and (b) the state/federal regulatory guidelines be updated for diagnostic laboratories, especially for those offering tests directly to the public (without a physician's request) to help protect the consumer.

Nutrigenomics and ethics interface: direct-to-consumer services and commercial aspects

A growing variety and number of genetic tests are advertised and sold directly to consumers (DTC) via the Internet, including nutrigenomic tests and associated products and services. Consumers have more access to genetic information about themselves, but access does not entail certainty about the implications of test results. Potential personal and public health harms and benefits are associated with DTC access to genetic testing services. Early policy responses to direct-to-consumer (DTC) genetic testing often involved calls for bans, and some jurisdictions prohibited DTC genetic tests. Recent policy responses by oversight bodies acknowledge expansion in the range of DTC tests available and suggest that a "one-size-fits-all" regulatory approach is not appropriate for all genetic tests. This review discusses ethical and regulatory aspects of DTC genetic testing, focusing particularly on nutrigenomic tests. We identify policy options for regulating DTC genetic tests, including full or partial prohibitions, enforcement of existing truth-in-advertising laws, and more comprehensive information disclosure about genetic tests. We advocate the latter option as an important means to improve transparency about current evidence on the strengths and limits of gene-disease associations and allow consumers to make informed purchasing decisions in the DTC marketplace.

Helping older adults meet nutritional challenges

Prevention of premature chronic diseases is an important component of healthy aging. Nutrition education can help to reduce the risk of premature chronic diseases in some older adults. Home delivered meals and congregate dining services assist vulnerable elderly persons by providing opportunities for nutritional and social support. Screening and assessment tools identify factors affecting nutritional health and can also provide specific directions for planning, implementation, and evaluation of tailored interventions. Dietitians and allied health professionals are well positioned to assist a heterogeneous population of older adults in securing nutritional adequacy.

Nutrição no pós-genoma: fundamentos e aplicações de ferramentas ômicas

Após seqüenciamento do genoma humano, os estudos genômicos têm se voltado à elucidação das funções de todos os genes, bem como à caracterização de suas interações com fatores ambientais. A nutrigenômica surgiu no contexto do pós-genoma humano e é considerada área-chave para a nutrição nesta década. Seu foco de estudo baseia-se na interação gene-nutriente. Esta ciência recente tem como objetivo principal o estabelecimento de dietas personalizadas, com base no genótipo, para a promoção da saúde e a redução do risco de doenças crônicas não transmissíveis como as cardiovasculares, o câncer, o diabetes, entre outras. Nesse contexto, é fundamental a aplicação na área de nutrição das ferramentas de genômica funcional para análise do transcritoma (transcritômica), do proteoma (proteômica) e do metaboloma (metabolômica). As aplicabilidades dessas metodologias em estudos nutricionais parecem ilimitadas, pois podem ser conduzidas em cultura de células, modelos de experimentação em animais, estudos pré-clinicos e clínicos. Tais técnicas apresentam potencial para identificar biomarcadores que respondem especificamente a um determinado nutriente ou composto bioativo dos alimentos e para estabelecer as melhores recomendações dietéticas individuais para redução do risco das doenças crônicas não transmissíveis e promoção da saúde.

Patients, evidence and genes: an exploration of GPs' perspectives on gene-based personalized nutrition advice

BACKGROUND

Nutrigenomics science examines the response of individuals to food compounds using post-genomics technology. It is expected that in the future, personalized nutrition advice can be provided based on information about genetic make-up.

OBJECTIVES

Gene-based personalized nutrition advice emerges at the junction of different disciplines and technologies and may directly influence people's lives. Therefore, public concern is to be expected. Because GPs are gatekeepers of health care, their involvement in early stages of the development process is desirable.

METHOD

In 2006, 15 GPs were interviewed to collect their perceived barriers and opportunities towards involvement in gene-based nutrition advice. The interviews were qualitatively analysed with use of Atlas.ti, a qualitative analysis programme.

RESULTS

The participants held a mostly critical view towards such personalized nutrition advice. They argued that findings of nutritional studies lacked robustness, were not based on patients' needs and were often equivocal. And that a patient central perspective urges them to question consequences for patients. Participants argued that GPs should be involved in selecting and monitoring patients in nutrigenomics studies.

CONCLUSIONS

Early involvement of GPs in the development process is needed to allow for the integration of their practical, social and ethical considerations in the technical and scientific agendas. However, the background of their critical attitude towards nutrigenomics-based personalized nutrition, and nutrition advice more generally, has to be explored further. To facilitate a joint learning process and to improve socio-technical decision making with respect to this innovation, initiatives that allow different stakeholders to exchange their perspectives should be organized.

Genotype-phenotype associations: modulation by diet and obesity

Changes in diet are likely to reduce chronic disorders, but after decades of active research and heated discussion, the question still remains: what is the optimal diet to achieve this elusive goal? Is it a low-fat diet, as traditionally recommended by multiple medical societies? Or a high monounsaturated fat (MUFA) diet as predicated by the Mediterranean diet? Perhaps a high polyunsaturated fat (PUFA) diet based on the cholesterol-lowering effects? The right answer may be all of the above but not for everybody. A well-known phenomenon in nutrition research and practice is the dramatic variability in interindividual response to any type of dietary intervention. There are many other factors influencing response, and they include, among many others, age, sex, physical activity, alcohol, and smoking as well as genetic factors that will help to identify vulnerable populations/individuals that will benefit from a variety of more personalized and mechanistic-based dietary recommendations. This potential could and needs to be developed within the context of nutritional genomics that in conjunction with systems biology may provide the tools to achieve the holy grail of dietary prevention and therapy of chronic diseases and cancer. This approach will break with the traditional public health approach of "one size fits all." The current evidence based on nutrigenetics has begun to identify subgroups of individuals who benefit more from a low-fat diet, whereas others appear to benefit more from high MUFA or PUFA diets. The continuous progress in nutrigenomics will allow some time in the future to provide targeted gene-based dietary advice.

Gene-environment interactions and susceptibility to metabolic syndrome and other chronic diseases

There is an intrinsic complexity in the pathogenesis of common diseases. The concept of gene-environment interaction is receiving support from emerging evidence coming primarily from studies involving diet and cardiovascular disease (CVD) and its various risk factors. The accumulating evidence shows that common variants at candidate genes for lipid metabolism, inflammation, and obesity are associated with altered plasma levels of classic and new biomarkers of metabolic syndrome and CVD risk. Major contributors to this knowledge have been a series of large population studies containing phenotype-rich databases and dietary information to which genetic data have been added. Although this approach has provided strong evidence supporting the concept of gene-diet interactions modulating CVD risk factors, the strength of the individual effect is very small, and the replication among studies is rather disappointing. Current population studies are starting to incorporate experimental and analytical approaches that could provide more solid and comprehensive results. However, other limitations, such as the size of the populations required to examine higher-level interactions, are still major obstacles to translating this knowledge into practical public health applications. Nevertheless, data from numerous molecular and genetic epidemiological studies provide tantalizing evidence suggesting that gene-environment interactions, i.e., the modulation by a genetic polymorphism of a dietary component effect on a specific phenotype (e.g., cholesterol levels and obesity), can interact in ways that increase the risk for developing chronic disease, including susceptibility to developing the metabolic syndrome. Once further experience is gained from patients and/or individuals at high risk, more personalized genetic-based approaches may be applied toward the primary prevention and treatment of CVDs and other complex inflammatory diseases.

Using genomic biology to study liver metabolism

The liver plays a central role in coordinating the body's metabolism, including glucose homeostasis, xenobiotic metabolism and detoxification, and steroid hormone synthesis and degradation. Many of the regulatory effects in response to diet initially occur in the liver, which then modulates the activities of other organs in terms of nutrient utilization and metabolism. The health consequences of abnormal liver function are widespread, many of which are not entirely understood. Recent advances in genomic biology, nanotechnology, computer science and related fields have supplied researchers with a powerful set of tools for the laboratory and clinic. Because nutrient status has been proven to be an important factor in health and disease, the use of these tools to identify nutrient-gene interactions and their association with disease has greatly increased over the past decade. Given its great importance to intermediary metabolism, the liver has been one of the primary organs of focus in recent nutrigenomic experiments. This paper will provide a brief synopsis of the recent technological advancements that may be applied to nutrition research, common mechanisms by which nutrients and genes interact with one another, a few examples pertaining to hepatic function, and future directions in the field.

Integrating anticipated nutrigenomics bioscience applications with ethical aspects

Nutrigenomics is a subspecialty of nutrition science which aims to understand how gene-diet interactions influence individuals' response to food, disease susceptibility, and population health. Yet ethical enquiry into this field is being outpaced by nutrigenomics bioscience. The ethical issues surrounding nutrigenomics face the challenges of a rapidly evolving field which bring forward the additional dimension of crossdisciplinary integrative research between social and biomedical sciences. This article outlines the emerging nutrigenomics definitions and concepts and analyzes the existing ethics literature concerning personalized nutrition and presents "points to consider" over ethical issues regarding future nutrigenomics applications. The interest in nutrigenomics coincides with a shift in emphasis in medicine and biosciences toward prevention of future disease susceptibilities rather than treatment of already established disease. Hence, unique ethical issues emerge concerning the extent to which nutrigenomics can alter our relation to food, boundaries between health and disease, and the folklore of medical practice. Nutrigenomics can result in new social values, norms, and responsibilities for both individuals and societies. Nutrigenomics is not only another new application of "-omics" technologies in the context of gene-diet interactions. Nutrigenomics may fundamentally change the way we perceive human illness while shifting the focus and broadening the scope of health interventions from patients to healthy individuals. In resource- and time-limited healthcare settings, this creates unique ethical dilemmas and distributive justice issues. Ethical aspects of nutrigenomics applications should be addressed proactively, as this new science develops and increasingly coalesces with other applications of genomics in medicine and public health.

Ethical, legal and social issues in nutrigenomics: the challenges of regulating service delivery and building health professional capacity

Nutrigenomics, the conjunction of molecular nutrition with human genomics, is among the first publicly available applications of the human genome project. Nutrigenomics raises ethical, legal and social issues particularly with respect to how the public may access nutrigenetic tests and associated nutritional and lifestyle advice. Current regulatory controversy focuses on potential harms associated with direct-to-consumer (DTC) marketing of nutrigenetic tests and especially the need to protect consumers from unreliable tests, false claims and unproven dietary supplements. Nutrigenomics does, however, offer the potential of important health benefits for some individuals. The regulation of nutrigenomic services is slowly evolving, but there is little indication of increased professional capacity to support service delivery. Primary care physicians have minimal training in nutrition and genetics, and medical geneticists are in high demand and short supply. Dietetic practitioners are experts in nutrition science and interest in nutrigenomics is growing among members of this professional group. However, as with physicians, dietetics practitioners would require considerable training to bring nutrigenomics into their practice capacity. A downside of regulatory restrictions on direct consumer access to nutrigenomics companies is that responsible businesses may be hindered in meeting emergent public demand while health care professional groups have not yet developed capacity to provide nutrigenomics services.

Nutrigenomics and gut health

Recognition of the interplay between genes and diet in development of disease and for maintenance of optimal metabolism has led to nutrigenomic or nutrigenetic approaches to personalising or individualising nutrition, with the potential of preventing, delaying, or reducing the symptoms of chronic diseases. Some of the development work has focussed on cardiovascular disease or type II diabetes mellitus, where various groups have identified potential diet-gene interactions. However, the available studies also emphasise the exponential increase in numbers of subjects necessary to recruit for clinical evaluation if we are to successfully provide informative high-dimensional datasets of genetic, nutrient, metabolomic (clinical), and other variables. There is also a significant bioinformatics challenge to analyze these. To add to the complexity, many of the pioneering studies had assumed that single nucleotide polymorphisms (SNPs) were the main source of human variability, but an increasing evidence base suggests the importance of more subtle gene regulatory mechanisms, including copy number variants. As an example, the risk of Inflammatory Bowel Disease (IBD) is associated with the inheritance of a number of contributory SNPs as well as with copy number variants of certain other genes. The variant forms of genes often result in disruptions to bacterial homeostasis mechanisms or to signal transduction of the intestinal epithelial cell of the host, and thereby to altered intestinal barrier function, and/or adaptive immune responses. The human gut microbiota is altered in individuals suffering from disorders such as IBD, and probiotic or prebiotic therapies or elemental diets may be beneficial to a high proportion of individuals through modifying the gut microbiota, and also modulating immune responses. New putative foods or dietary therapies may be identified through novel tissue culture screens, followed by further testing with in vivo animal models of human disease. A scientifically based rationale for developing novel foods related to genotype might use a combination of food fractionation, testing in tissue culture models and validation through animal models, before moving into human populations. However, the field of nutrigenomics raises ethical, legal and social issues, and will be of genuine benefit to human health only if developed in linkage with adequately trained health professionals. Such training will widen public understanding, and permit dialogue with regulatory officials to responsibly develop, apply and progress this new field.

Nutrigenetics and nutraceuticals: the next wave riding on personalized medicine

The Human Genome Project and subsequent identification of single nucleotide polymorphisms (SNPs) within populations has played a major role in predicting individual response to drugs (pharmacogenetics) leading to the concept of "personalized medicine." Nutritional genomics is a recent off-shoot of this genetic revolution that includes (1) nutrigenomics: the study of interaction of dietary components with the genome and the resulting proteonomic and metabolomic changes; and (2) nutrigenetics: understanding the gene-based differences in response to dietary components and developing nutraceuticals that are most compatible with health based on individual genetic makeup. Despite the extensive data on genetic polymorphisms in humans, its translation into medical practice has been slow because of the time required to accumulate population data on SNP incidence, understand the significance of a given SNP in disease, and develop suitable diagnostic tests. Nutrigenomics revitalized the field by showing that nutrients and botanicals can interact with the genome and modify subsequent gene expression, which has provided a great impetus for nutrigenetic research and nutraceutical development based on nutrigenetics. Polymorphisms in methlyene tetrahydrofolate reductase (MTHFR) (involved in folate metabolism), apolipoprotein E (Apo E) and ApoA1 (in cardiovascular disease), and leptin/leptin receptor (obesity) genes are some good examples for understanding basic nutrigenetics. Developing nutraceuticals to prevent and manage thrombosis risk in women with thrombophilic gene mutations are discussed in the context of the opportunities that exist at the nutrigenetic/pharmacogenetic interphase leading to "personalized nutrition." Further research on individual differences in genetic profiles and nutrient requirements will help establish nutrigenetics as an essential discipline for nutrition and dietetics practice.

The response of lipoproteins to dietary fat and cholesterol in lean and obese persons

Individuals differ in the response of their blood lipoproteins to cholesterol-lowering diets. One characteristic clearly associated with susceptibility to diet is leanness; many studies show that total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol concentrations respond more strongly to dietary fat and cholesterol in lean subjects than in obese subjects. This is unlikely to be due to differences in dietary compliance. A metabolic explanation is that obese people have a higher rate of total body cholesterol synthesis. The low-density lipoprotein receptors in their liver cells are partly suppressed by this large stream of endogenous cholesterol coming in from their enterohepatic circulation, and the amount added by dietary cholesterol relative to the endogenous pool would be less than in lean people. Whatever the mechanism, diets low in saturated fat and cholesterol are less effective in the obese. The most effective way for obese people to normalize their blood lipids is to lose weight, which is, unfortunately, hard to do in our society.

Nutrigenetics, plasma lipids, and cardiovascular risk

Cardiovascular disease (CVD) results from complex interactions between genetic and environmental factors. The evidence supports that gene-environment interactions modulate plasma lipid concentrations and potentially CVD risk. Several genes (eg, apolipoprotein A-I and A-IV, apolipoprotein E, and hepatic lipase) are providing proof-of-concept for the application of genetics in the context of personalized nutrition for CVD prevention. The spectrum of candidate genes has been expanding to incorporate those involved in intracellular lipid metabolism and especially those transcription factors (ie, peroxisome proliferator activator receptors) that act as sensors of nutrients in the cell (eg, polyunsaturated fatty acids) to trigger metabolic responses through activation of specific sets of genes. However, current knowledge is still very limited and so is the potential benefit of its application to clinical practice. Thinking needs to evolve from simple scenarios (eg, one single dietary component, a single nucleotide polymorphism and risk factor) to more realistic situations involving multiple interactions. One of the first situations where personalized nutrition is likely to be beneficial is in patients with dyslipidemia who require special intervention with dietary treatment. This process could be more efficient if the recommendations were carried out based on genetic and molecular knowledge. Moreover, adherence to dietary advice may increase when it is supported with information based on nutritional genomics, and a patient believes the advice is personalized. However, a number of important changes in the provision of health care are needed to achieve the potential benefits associated with this concept, including a teamwork approach with greater integration among physicians, food and nutrition professionals, and genetic counselors.

Continuing Education Needs of Registered Dietitians Regarding Nutrigenomics

The purpose of this study was to assess continuing education needs for registered dietitians regarding application of the science of nutritional genomics in clinical settings. A cross-sectional survey was mailed to a random national sample of 2,500 registered dietitians with a 40% response rate (n=995). The survey assessed knowledge; attitudes related to benefits and barriers to application; perceptions of consumer motivators and barriers; attitudes regarding ethical, legal, and social issues; and preferences for continuing education. Differences were determined according to year of registration using nonparametric Kruskal-Wallis tests. Survey respondents had little previous exposure to nutrigenomics, had not applied nutrigenomics in their practice in the past year, and were not confident in their ability to apply nutrigenomics in a clinical setting, but were interested in learning more about its application. Few differences existed in attitudes about benefits and barriers to application of nutrigenomics by year of registration. The most favored learning activity for continuing education was seminars/workshops. The most important content areas for continuing education were foundational knowledge, application, and communication to the lay public. Continuing education should focus on these content areas to allow application based on the supporting science and ways to effectively communicate the information to consumers.