The concept of plant-based diets has become popular due to the purported benefits for both human health and environmental impact. Although ‘plant-based’ is sometimes used to indicate omnivorous diets with a relatively small component of animal foods, here we take it to mean either vegetarian (plant-based plus dairy products and/or eggs) or vegan (100% plant-based). Important characteristics of plant-based diets which would be expected to be beneficial for long-term health are low intakes of saturated fat and high intakes of dietary fibre, whereas potentially deleterious characteristics are the risk of low intakes of some micronutrients such as vitamin B12, vitamin D, calcium and iodine, particularly in vegans. Vegetarians and vegans typically have lower BMI, serum LDL cholesterol and blood pressure than comparable regular meat-eaters, as well as lower bone mineral density. Vegetarians in the EPIC-Oxford study have a relatively low risk of IHD, diabetes, diverticular disease, kidney stones, cataracts and possibly some cancers, but a relatively high risk of stroke (principally haemorrhagic stroke) and bone fractures, in comparison with meat-eaters. Vegans in EPIC-Oxford have a lower risk of diabetes, diverticular disease and cataracts and a higher risk of fractures, but there are insufficient data for other conditions to draw conclusions. Overall, the health of people following plant-based diets appears to be generally good, with advantages but also some risks, and the extent to which the risks may be mitigated by optimal food choices, fortification and supplementation is not yet known.

A plant-based diet, which can include small amounts of meat, is the foundation for healthy sustainable diets, which will have co-benefits for health, climate and the environment. Studies show that some of the barriers to making this dietary change and reducing meat consumption are perceptions that plant-based diets are inconvenient, it takes too much time and skills to prepare meals and ingredients are expensive. The food environment is changing and the industry is responding with the exponential increase in the market of highly processed, convenient and cheap plant-based foods. This overcomes some of the barriers, but there is concern about whether they are healthy and environmentally sustainable. Plant-based foods have a halo effect around health and the environment, but many being produced are ultra-processed foods that are high in energy, fat, sugar and salt and have a higher environmental impact than minimally processed plant-based foods. The trend towards eating more highly processed plant-based convenience foods is a concern with regard to both public health and the targets set to reduce greenhouse gas (GHG) emissions. The ‘modern day’ plant-based diet emerging is very different to a more traditional one comprising pulses, vegetables and wholegrain. Studies show that those who are younger and have been a vegetarian for a shorter duration are eating significantly more ultra-processed plant-based foods. While there is a place for convenient, desirable and affordable plant-based food to encourage dietary change, care should be taken that this does not subconsciously set a path which may ultimately be neither healthy nor sustainable.

The aim of this review is to provide an overview of the complex interactions between dietary fibre and the resident microbial community in the human gut. The microbiota influences both health maintenance and disease development. In the large intestine, the microbiota plays a crucial role in the degradation of dietary carbohydrates that remain undigested in the upper gut (non-digestible carbohydrates or fibre). Dietary fibre contains a variety of different types of carbohydrates, and its breakdown is facilitated by many different microbial enzymes. Some microbes, termed generalists, are able to degrade a range of different carbohydrates, whereas others are more specialised. Furthermore, the physicochemical characteristics of dietary fibre, such as whether it enters the gut in soluble or insoluble form, also likely influence which microbes can degrade it. A complex nutritional network therefore exists comprising primary degraders able to attack complex fibre and cross feeders that benefit from fibre breakdown intermediates or fermentation products. This leads predominately to the generation of the short-chain fatty acids (SCFA) acetate, propionate and butyrate, which exert various effects on host physiology, including the supply of energy, influencing glucose and lipid metabolism and anti-carcinogenic and anti-inflammatory actions. In order to effectively modulate the gut microbiota through diet, there is a need to better understand the complex competitive and cooperative interactions between gut microbes in dietary fibre breakdown, as well as how gut environmental factors and the physicochemical state of fibre originating from different types of diets influence microbial metabolism and ecology in the gut.

The observation that 64% of English adults are overweight or obese despite a rising prevalence in weight-loss attempts suggests our understanding of energy balance is fundamentally flawed. Weight-loss is induced through a negative energy balance; however, we typically view weight change as a static function, in that energy intake and energy expenditure are independent variables, resulting in a fixed rate of weight-loss assuming a constant energy deficit. Such static modelling provides the basis for the clinical assumption that a 14644 kJ (3500 kcal) deficit translates to a 1 lb weight-loss. However, this ‘3500 kcal (14644 kJ) rule’ is consistently shown to significantly overestimate weight-loss. Static modelling disregards obligatory changes in energy expenditure associated with the loss of metabolically active tissue, i.e. skeletal muscle. Additionally, it disregards the presence of adaptive thermogenesis, the underfeeding-associated fall in resting energy expenditure beyond that caused by loss of fat-free mass. This metabolic manipulation of energy expenditure is observed from the onset of energy restriction to maintain weight at a genetically pre-determined set point. As a result, the observed magnitude of weight-loss is disproportionally less, followed by earlier weight plateau, despite strict compliance to a dietary intervention. By simulating dynamic changes in energy expenditure associated with underfeeding, mathematical modelling may provide a more accurate method of weight-loss prediction. However, accuracy at an individual level is limited due to difficulty estimating energy requirements, physical activity and dietary intake in free-living individuals. In the present paper, we aim to outline the contribution of dynamic changes in energy expenditure to weight-loss resistance and weight plateau.

Lower household income has been consistently associated with poorer diet quality and poorer dietary health outcomes. Households experiencing poverty find themselves unable to afford enough food, and the food that they can afford is often poor quality, energy dense and low in nutrients. However, the relationship between diet, poverty and health is complex. Not everyone on a low income has a poor diet. Poverty is about more than low incomes and it is not a uniform experience. Particular aspects of the experience of poverty have implications for diet and dietary health. It is increasingly apparent that uncertainty is one of those aspects. Recession, welfare policy, employment trends and widening inequality have created more uncertainty for those on low incomes. In the context of heightened uncertainty, all aspects of household food provisioning – including budgeting, shopping, storage, meal planning and cooking – are more difficult and sometimes impossible. This review will draw on research about food practices and dietary health in low-income neighbourhoods to explore the ways in which experiences of prolonged uncertainty shape dietary practices and impact health and well-being.

Research characterising the gut microbiota in different populations and diseases has mushroomed since the advent of next-generation sequencing techniques. However, there has been less emphasis on the impact of dietary fibres and other dietary components that influence gut microbial metabolic activities. Dietary fibres are the main energy source for gut bacteria. However, fibres differ in their physicochemical properties, their effects on the gut and their fermentation characteristics. The diversity of carbohydrates and associated molecules in fibre-rich foods can have a major influence on microbiota composition and production of bioactive molecules, for example SCFAs and phenolic acids. Several of these microbial metabolites may influence the functions of body systems including the gut, liver, adipose tissues and brain. Dietary fibre intake recommendations have recently been increased (to 30 g daily) in response to growing obesity and other health concerns. Increasing intakes of specific fibre and plant food sources may differentially influence the bacteria and their metabolism. However, in vitro studies show great individual variability in the response of the gut microbiota to different fibres and fibre combinations, making it difficult to predict which foods or food components will have the greatest impact on levels of bioactive molecules produced in the colon of individuals. Greater understanding of individual responses to manipulation of the diet, in relation to microbiome composition and production of metabolites with proven beneficial impact on body systems, would allow the personalised approach needed to best promote good health.

Iron is essential for the functioning of all cells and organs, most critically for the developing brain in the fundamental neuronal processes of myelination, energy and neurotransmitter metabolism. Iron deficiency, especially in the first 1000 days of life, can result in long-lasting, irreversible deficits in cognition, motor function and behaviour. Pregnant women, infants and young children are most vulnerable to iron deficiency, due to their high requirements to support growth and development, coupled with a frequently inadequate dietary supply. An unrecognised problem is that even if iron intake is adequate, common pregnancy-related and lifestyle factors can affect maternal–fetal iron supply in utero, resulting in an increased risk of deficiency for the mother and her fetus. Although preterm birth, gestational diabetes mellitus and intrauterine growth restriction are known risk factors, more recent evidence suggests that maternal obesity and delivery by caesarean section further increase the risk of iron deficiency in the newborn infant, which can persist into early childhood. Despite the considerable threat that early-life iron deficiency poses to long-term neurological development, life chances and a country's overall social and economic progress, strategies to tackle the issue are non-existent, too limited or totally inappropriate. Prevention strategies, focused on improving the health and nutritional status of women of reproductive age are required. Delayed cord clamping should be considered a priority. Better screening strategies to enable the early detection of iron deficiency during pregnancy and early-life should be prioritised, with intervention strategies to protect maternal health and the developing brain.

With approximately two in three UK adults overweight or obese, one in five living in poverty and our emergence from the Covid-19 pandemic with implications for employment and income status there is an urgent need to understand what it costs to eat healthily and the role that promotions can play in helping householders manage food budgets. The literature suggests that, in affluent countries, price promotions appear to increase consumer food purchases and are applied more frequently to less healthy products than their healthy counterparts. This review discusses the cost of a healthy diet, identifies the prevalence of promotions in both the supermarket setting generally and a typical shopping basket specifically, and discusses the barriers to affording a healthy diet. Given the current policy focus on the cost of living and population health emphasising the need for food shopping to represent health and value for money for better public health outcomes, this review contributes to the evidence base for retailers' and policymakers' consideration as policy solutions are sought to reduce population obesity levels, while ensuring the affordability and accessibility of nutritious food. It is important, given the shift in consumer purchasing behaviour to online shopping as a result of self-isolating or reticence to physically access stores in response to the Covid-19 pandemic, that retail food promotions are available irrespective of the chosen mode of shopping (in-store or online).

Gene–nutrient interactions (GeNuIne) collaboration, a large-scale collaborative project, has been initiated to investigate the impact of gene–nutrient interactions on cardiometabolic diseases using population-based studies from ethnically diverse populations. In this project, the relationship between deficiencies of vitamins B12 and D, and metabolic diseases was explored using a nutrigenetic approach. A genetic risk score (GRS) analysis was used to examine the combined effect of several genetic variations that have been shown to be associated with metabolic diseases and vitamin B12 and D deficiencies, respectively. In Sri Lankan, Indonesian and Brazilian populations, those carrying a high B12-GRS had an increased risk of metabolic diseases under the influence of dietary protein, fibre and carbohydrate intakes, respectively; however, in Asian Indians, genetically instrumented metabolic disease risk showed a significant association with low vitamin B12 status. With regards to nutrigenetic studies on vitamin D status, although high metabolic-GRS showed an interaction with dietary carbohydrate intake on vitamin D status, the study in Indonesian women demonstrated a vitamin D GRS–carbohydrate interaction on body fat percentage. In summary, these nutrigenetic studies from multiple ethnic groups have provided evidence for the influence of the dietary factors on the relationship between vitamin B12/D deficiency and metabolic outcomes. Furthermore, these studies highlight the existence of genetic heterogeneity in gene–diet interactions across ethnically diverse populations, which further implicates the significance of personalised dietary approaches for the prevention of these micronutrient deficiencies and metabolic diseases.

Micronutrient malnutrition, the deficiency of vitamins or minerals, impacts on physical and mental health, in clinical and general populations, across the life course. In older western populations the high prevalence and impact of micronutrient malnutrition is less well recognised. Low- and middle-income countries are experiencing the ‘double burden of disease’ where malnutrition coexists alongside the non-communicable diseases of aging, obesity, type 2 diabetes and cardiovascular disease. Held in December 2020, the Winter Conference of the Nutrition Society was designed to cover new areas of research and concern in micronutrient malnutrition across the life course. Common themes arising from the conference were: 1) The continuing high prevalence of micronutrient malnutrition across the life-course, in diverse populations, in high, middle and low-income countries. 2) That multiple deficiencies of micronutrients frequently exist. 3) The primary cause of deficiency is poor quality diets, of low diversity, low in micronutrient dense foods. 4) Clinical conditions, medications for common non-communicable diseases, and environmental conditions, interact with and exacerbate the effects of poor diet quality. 5) Understanding of the mechanistic effects of micronutrients is still emerging. 6) Micronutrients are necessary for maintaining immune function, which has importance for the COVID-19 epidemic. 7) Better biomarkers are needed detect and understand the effects of deficiency. 7) Dietary recommendations need to be updated regularly. Further research is needed in all these areas. Comprehensive public health and government approaches to ensure access and affordability of good quality foods to populations of all ages, particularly during the ongoing COVID-19 epidemic, are crucial.

Sarcopenia, a skeletal muscle disorder that is characterised by loss of muscle strength and mass, is common in older populations and associated with poorer health outcomes. Although the individual and economic costs of sarcopenia are widely recognised, current understanding of its pathophysiology is incomplete, limiting efforts to translate research evidence into effective preventive and treatment strategies. While nutrition is a key field of sarcopenia research, the role of differences in habitual diets, and the effectiveness of dietary change as a prevention or treatment strategy, is uncertain. There is a growing evidence base that links low micronutrient intakes to sarcopenia risk and/or its components (low muscle strength and mass, impaired physical performance), although there remain many gaps in understanding. There is some consistency in findings across studies highlighting potential roles for antioxidant nutrients, B vitamins and magnesium; however, the evidence is largely observational and from cross-sectional studies, often describing associations with different muscle outcomes. As low intakes of some micronutrients are common in older populations, there is a need for new research, particularly from well-characterised prospective cohorts, to improve the understanding of their role and importance in the aetiology of sarcopenia and to generate the evidence needed to inform dietary guidelines to promote muscle health.

In an ageing society, the preservation of health and function is becoming increasingly important. The present paper acknowledges that ageing is malleable and focuses on diets and key nutritional concerns later in life. It presents evidence for the importance of healthful dietary patterns and points towards specific nutritional concerns later in life and conveys three main messages: (1) considering health maintenance and malnutrition risk, both dietary quality in terms of healthful dietary patterns and dietary quantity are important later in life, (2) ageing-related changes in nutrient physiology and metabolism contribute to the risk of inadequacies or deficiencies for specific nutrients, e.g. vitamin D, vitamin B12 and protein and (3) that current food-based dietary guidelines propagate a shift into the direction of Mediterranean type of diets including more plant-based foods. Limited scientific evidence on nutritional requirements of older adults, along with envisaged shifts towards diets rich in plant foods, are challenges that need to be addressed in order to develop tailored nutritional recommendations and dietary guidance for older adults.

Magnesium (Mg2+) plays an essential role in many biological processes. Mg2+ deficiency is therefore associated with a wide range of clinical effects including muscle cramps, fatigue, seizures and arrhythmias. To maintain sufficient Mg2+ levels, (re)absorption of Mg2+ in the intestine and kidney is tightly regulated. Genetic defects that disturb Mg2+ uptake pathways, as well as drugs interfering with Mg2+ (re)absorption cause hypomagnesemia. The aim of this review is to provide an overview of the molecular mechanisms underlying genetic and drug-induced Mg2+ deficiencies. This leads to the identification of four main mechanisms that are affected by hypomagnesemia-causing mutations or drugs: luminal transient receptor potential melastatin type 6/7-mediated Mg2+ uptake, paracellular Mg2+ reabsorption in the thick ascending limb of Henle's loop, structural integrity of the distal convoluted tubule and Na+-dependent Mg2+ extrusion driven by the Na+/K+-ATPase. Our analysis demonstrates that genetic and drug-induced causes of hypomagnesemia share common molecular mechanisms. Targeting these shared pathways can lead to novel treatment options for patients with hypomagnesemia.

The aim of this review paper is to explore the strategies employed to tackle micronutrient deficiencies with illustrations from field-based experience. Hidden hunger is the presence of multiple micronutrient deficiencies (particularly iron, zinc, iodine and vitamin A), which can occur without a deficit in energy intake as a result of consuming an energy-dense, but nutrient-poor diet. It is estimated that it affects more than two billion people worldwide, particularly in low- and middle-income countries where there is a reliance on low-cost food staples and where the diversity of the diet is limited. Finding a way to improve the nutritional quality of diets for the poorest people is central to meeting the UN sustainable development goals particularly sustainable development goal 2: end hunger, achieve food security and improved nutrition and promote sustainable agriculture. As we pass the midpoint of the UN's Decade for Action on Nutrition, it is timely to reflect on progress towards achieving sustainable development goal 2 and the strategies to reduce hidden hunger. Many low- and middle-income countries are falling behind national nutrition targets, and this has been exacerbated by the COVID-19 pandemic as well as other recent shocks to the global food system which have disproportionately impacted the world's most vulnerable communities. Addressing inequalities within the food system must be central to developing a sustainable, cost-effective strategy for improving food quality that delivers benefit to the seldom heard and marginalised communities.

Policy decisions and the practice of public health nutrition need to be based on solid evidence, developed through rigorous research studies where objective measures are used and results that run counter to dogma are not dismissed but investigated. In recent years, enhancements in study designs, and methodologies for systematic reviews and meta-analysis, have improved the evidence-base for nutrition policy and practice. However, these still rely on a full appreciation of the strengths and limitations of the measures on which conclusions are drawn and on the thorough investigation of outcomes that do not fit expectations or prevailing convictions. The importance of ‘hard facts’ and ‘misfits’ in research designed to advance knowledge and improve public health nutrition is illustrated in this paper through a selection of studies from different stages in my research career, focused on the nutritional requirements of resource-poor populations in Africa and Asia.

The objectives are to present an updated synopsis on osteosarcopenic adiposity (OSA) syndrome and evaluate the roles of selected micronutrients in its prevention and management. OSA refers to the concurrent deterioration of bone (osteopenia/osteoporosis), muscle (sarcopenia) and adipose tissue expansion. It portrays the most advanced stage in a continuum of body composition disorders. Although OSA has been widely studied involving the populations of different backgrounds, its prevalence is hard to collate because different methodologies and criteria were used for its diagnosis. Another critical health aspect is the presence of low-grade chronic inflammation (LGCI) which contributes to OSA and vice versa. Nutrition is important in the prevention and management of both OSA and LGCI. Although micronutrients act in numerous metabolic and physiological processes, their roles here are presented in relation to OSA (and its components) and LGCI in general and relevant to the COVID-19 pandemic. These include calcium, magnesium, phosphorus, potassium, sodium and vitamins D and K; their interactions, physiological ratios and synergism/antagonism are discussed as well. In conclusion, calcium, magnesium and vitamin D have a profound impact on OSA and its components, and the latter two also on LGCI. Potassium and vitamin K are vital in bone, muscle functioning and possibly adipose tissue modification. Both, but particularly vitamin D, surfaced as important modulators of immune system with application in COVID-19 infections. While both phosphorus and sodium have important roles in bone, muscle and can impact adiposity, due to their abundance in food, their intake should be curbed to prevent possible damaging effects.

For many people, micronutrient requirement means the amount needed in the diet to ensure adequacy. Dietary reference values (DRV) provide guidance on the daily intake of vitamins and minerals required to ensure the needs of the majority in the population are covered. These are developed on estimates of the quantity of each micronutrient required by the average person, the bioavailability of the micronutrient from a typical diet and the interindividual variability in these amounts. Sex differences are inherent in the requirements for many micronutrients because they are influenced by body size or macronutrient intake. These are reflected in different DRV for males and females for some micronutrients, but not all, either when data from males and females are combined or when there is no evidence of sex differences. Pregnancy and lactation represent times when micronutrient requirements for females may differ from males, and separate DRV are provided. For some micronutrients, no additional requirement is indicated during pregnancy and lactation because of physiological adaptations. To date, little account has been taken of more subtle sex differences in growth and maturation rates, health vulnerabilities and in utero and other programming effects. Over the years, the MRC Nutrition and Bone Health Group has contributed data on micronutrient requirements across the lifecourse, particularly for calcium and vitamin D, and shown that supplementation can have unexpected sex-specific consequences that require further investigation. The present paper outlines the current issues and the need for future research on sex differences in micronutrient requirements.

Global population growth, increased life expectancy and climate change are all impacting world's food systems. In industrialised countries, many individuals are consuming significantly more protein than needed to maintain health, with the majority being obtained from animal products, including meat, dairy, fish and other aquatic animals. Current animal production systems are responsible for a large proportion of land and fresh-water use, and directly contributing to climate change through the production of greenhouse gases. Overall, approximately 60% of the global protein produced is used for animal and fish feed. Concerns about their impact on both human, and planetary health, have led to calls to dramatically curb our consumption of animal products. Underutilised plants, insects and single-cell organisms are all actively being considered as alternative protein sources. Each present challenges that need to be met before they can become economically viable and safe alternatives for food or feed. Many plant species contain anti-nutritional factors that impair the digestion and absorption of protein and micronutrients. Insects represent a potentially rich source of high-quality protein although, questions remain relating to digestibility, allergenicity and biosecurity. Algae, fungi and bacteria are also a rich source of protein and there is growing interest in the development of ‘cultured meat’ using stem cell technology. For the foreseeable future, it appears likely that the ‘protein-economy’ will remain mixed. The present paper reviews progress and future opportunities in the development of novel protein sources as food and animal feed.

All human tissues are in a constant state of remodelling, regulated by the balance between tissue protein synthesis and breakdown rates. It has been well-established that protein ingestion stimulates skeletal muscle and whole-body protein synthesis. Stable isotope-labelled amino acid methodologies are commonly applied to assess the various aspects of protein metabolism in vivo in human subjects. However, to achieve a more comprehensive assessment of post-prandial protein handling in vivo in human subjects, intravenous stable isotope-labelled amino acid infusions can be combined with the ingestion of intrinsically labelled protein and the collection of blood and muscle tissue samples. The combined application of ingesting intrinsically labelled protein with continuous intravenous stable isotope-labelled amino acid infusion allows the simultaneous assessment of protein digestion and amino acid absorption kinetics (e.g. release of dietary protein-derived amino acids into the circulation), whole-body protein metabolism (whole-body protein synthesis, breakdown and oxidation rates and net protein balance) and skeletal muscle metabolism (muscle protein fractional synthesis rates and dietary protein-derived amino acid incorporation into muscle protein). The purpose of this review is to provide an overview of the various aspects of post-prandial protein handling and metabolism with a focus on insights obtained from studies that have applied intrinsically labelled protein under a variety of conditions in different populations.

Populations' diets typically fall short of recommendations. The implication of this on ill health and quality of life is well established, as are the subsequent health care costs. An area of growing interest within public health nutrition is food choice architecture; how a food choice is framed and its influence on subsequent food selection. In particular, there is an appeal to manipulating the choice architecture in order to nudge individuals' food choice. This review outlines the current understanding of food choice architecture, theoretical background to nudging and the evidence on the effectiveness of nudge strategies, as well as their design and implementation. Interventions emphasising the role of nudge strategies have investigated changes to the accessibility, availability and presentation of food and the use of prompts. Empirical studies have been conducted in laboratories, online and in real-world food settings, and with different populations. Evidence on the effectiveness of nudge strategies in shifting food choice is encouraging. Underpinning mechanisms, not yet fully explicated, are proposed to relate to salience, social norms and the principle of least effort. Emerging evidence points to areas for development including the effectiveness of choice architecture interventions with different and diverse populations, and the combined effect of multiple nudges. This, alongside further examination of theoretical mechanisms and guidance to engage and inspire across the breadth of food provision, is critical. In this way, the potential of choice architecture to effect meaningful change in populations' diets will be realised.