Observational research, mainly prospective cohort studies (PCS), has represented a long-standing challenge for those attempting to draw up consistent policy recommendations in the area of diet and health. This has been due to the inherent limitations in ascribing causality from observed associations due to problems of confounding of the findings and publication and citation bias. Developments in nutritional epidemiology research over the past 20–30 years have enabled causal criteria to be derived from observational studies and the totality of the primary literature to be reviewed objectively, reducing previous focus on narrative accounts of individual studies. The gold standard approach to assessing causal relationships is via randomised controlled trials (RCT), but neither RCT nor PCS provide direct evidence for biological plausibility, which is a key criterion for assessing causality. Although extensive mechanistic data are available in the literature, a systematic approach to select and assess quality and relevance of published studies has not been available. This limits their use in the development of diet and health policy. Recent studies have investigated a proposed two-step framework and novel methodologies for integrating heterogeneous data from cell, animal and human studies. Pilot and feasibility studies have shown this to be a useful novel approach to studies of diet and cancer, but further refinements are required, including development of appropriate quality criteria which are less dependent on RCT designs. Future studies are needed to fully verify the approach and its potential for use in other diet–disease relationships.

Nutrients can impact and regulate cellular metabolism and cell function which is particularly important for the activation and function of diverse immune subsets. Among the critical nutrients for immune cell function and fate, glutamine is possibly the most widely recognised immunonutrient, playing key roles in TCA cycle, heat shock protein responses and antioxidant systems. In addition, glutamine is also involved with inter-organ ammonia transport, and this is particularly important for not only immune cells, but also to the brain, especially in catabolic situations such as critical care and extenuating exercise. The well characterised fall in blood glutamine availability has been the main reason for studies to investigate the possible effects of glutamine replacement via supplementation but many of the results are in poor agreement. At the same time, a range of complex pathways involved in glutamine metabolism have been revealed via supplementation studies. This article will briefly review the function of glutamine in the immune system, with emphasis on metabolic mechanisms, and the emerging role of glutamine in the brain glutamate/gamma-amino butyric acid cycle. In addition, relevant aspects of glutamine supplementation are discussed.

Obesity, excess adipose tissue accumulation that may impair health, is a major global healthcare challenge that increases the risk of several life-limiting diseases, reduces quality of life and leads to premature mortality. Weight loss improves or leads to the resolution of obesity-related diseases. Lifestyle interventions are the cornerstone for all weight management programmes and lead to health benefits. However, for the majority of people with severe obesity, lifestyle interventions and currently available anti-obesity medications lead to insufficient weight loss to improve their health. For these patients the only effective treatment option is bariatric surgery, which whilst highly effective, is difficult to access and not suitable for everyone, leaving a ‘treatment gap’ between lifestyle interventions and bariatric surgery. Unfortunately, the history of development of drugs to treat obesity has been marred by poor efficacy and safety issues. This is now set to change as a result of scientific advancements, which have increased the understanding of the role that gut hormones play in regulating energy and glucose homoeostasis. This has led to the development of effective, safe drugs based on gut hormones that target the body's own appetite regulating systems that herald a new era of treatments for people living with obesity.

Dietary patterns (DP) rich in plant foods are associated with improved health and reduced non-communicable disease risk. In October 2021, the Nutrition Society hosted a member-led conference, held online over 2 half days, exploring the latest research findings examining plant-rich DP and health. The aim of the present paper is to summarise the content of the conference and synopses of the individual speaker presentations are included. Topics included epidemiological analysis of plant-rich DP and health outcomes, the effects of dietary interventions which have increased fruit and vegetable (FV) intake on a range of health outcomes, how adherence to plant-rich DP is assessed, the use of biomarkers to assess FV intake and a consideration of how modifying behaviour towards increased FV intake could impact environmental outcomes, planetary health and food systems. In conclusion, although there are still considerable uncertainties which require further research, which were considered as part of the conference and are summarised in this review, adopting a plant-rich DP at a population level could have a considerable impact on diet and health outcomes, as well as planetary health.

Obesity and dyslipidaemia are strongly associated with the development of cardiometabolic diseases including CVD, stroke, type 2 diabetes, insulin resistance and non-alcoholic fatty liver disease. While these conditions are preventable, they are leading causes of mortality globally. There is now overwhelming clinical and experimental evidence that these conditions are driven by chronic systemic inflammation, with a growing body of data suggesting that this can be regulated by increasing levels of physical activity and reducing sedentary time. In this review we address the role of macrophage-mediated inflammation on the development of cardiometabolic diseases in individuals with overweight and obesity and how reducing sedentary behaviour and increasing physical activity appears to lessen these pro-inflammatory processes, reducing the risk of developing cardiometabolic diseases. While loss of subcutaneous and visceral fat mass is important for reducing chronic systemic inflammation, the mediating effects of increasing physical activity levels and lowering sedentary time on the development of inflamed adipose tissue also occur independently of changes in adiposity. The message that weight loss is not necessary for the benefits of physical activity in lowering chronic inflammation and improving health should encourage those for whom losing weight is difficult. Additionally, while the health benefits of meeting the recommended physical activity guidelines are clear, simply moving more appears to lower chronic systemic inflammation. Reducing sitting time and increasing light physical activity may therefore provide an alternative, more approachable manner for some with overweight and obesity to become more active, reduce chronic inflammation and improve cardiometabolic health.

Fatigue is defined as a symptom leading to the inability to continue functioning at the expected activity level. It is a highly prevalent symptom, challenging to frame into monodimensional pathophysiological mechanisms. As a result, fatigue is often underestimated in the clinical setting and is wrongly considered an unavoidable consequence of ageing. Several potential mechanisms responsible for fatigue have been proposed, including sleep patterns, autonomic nervous system abnormalities and biological complexity. Inflammation and mitochondrial dysfunction are among the most promising mechanisms through which malnutrition may cause fatigue. Not surprisingly, fatigue is highly prevalent in inflammatory conditions (e.g. COVID-19 infection). The nutritional status may also represent a critical factor in the development and presentation of fatigue, which may mimic the exhaustion of the individual's metabolic reserves. For example, the insufficient dietary intake of energy and proteins may determine the catabolism of body fat and muscles, disrupt the homeostatic balance and cause the onset of fatigue. It is necessary to conduct research on fatigue. By characterising its pathophysiological mechanisms, it will be possible to (1) support the design and development of targeted interventions, (2) improve the quality of life of many persons by acting on the symptom and (3) reduce the direct and indirect costs of a burdening condition typical of advancing age. In the present review, we provide an overview of the role that nutrition may play as a determinant of fatigue in older people, also in the context of the COVID-19 pandemic.

In this review, the relevance of selenium (Se) to viral disease will be discussed paying particular attention to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease (COVID-19). Se, the active centre in selenoproteins has an ongoing history of reducing the incidence and severity of viral infections. Host Se deficiency increased the virulence of RNA viruses such as influenza A and coxsackievirus B3, the latter of which is implicated in the development of Keshan disease in north-east China. Significant clinical benefits of Se supplementation have been demonstrated in HIV-1, in liver cancer linked to hepatitis B, and in Chinese patients with hantavirus that was successfully treated with oral sodium selenite. China is of particular interest because it has populations that have both the lowest and the highest Se status in the world. We found a significant association between COVID-19 cure rate and background Se status in Chinese cities; the cure rate continued to rise beyond the Se intake required to optimise selenoproteins, suggesting an additional mechanism. Se status was significantly higher in serum samples from surviving than non-surviving COVID-19 patients. As regards mechanism, SARS-CoV-2 may interfere with the human selenoprotein system; selenoproteins are important in scavenging reactive oxygen species, controlling immunity, reducing inflammation, ferroptosis and endoplasmic reticulum (ER) stress. We found that SARS-CoV-2 significantly suppressed mRNA expression of GPX4, of the ER selenoproteins, SELENOF, SELENOM, SELENOK and SELENOS and down-regulated TXNRD3. Based on the available data, both selenoproteins and redox-active Se species (mimicking ebselen, an inhibitor of the main SARS-CoV-2 protease that enables viral maturation within the host) could employ their separate mechanisms to attenuate virus-triggered oxidative stress, excessive inflammatory responses and immune-system dysfunction, thus improving the outcome of SARS-CoV-2 infection.

There is an ever increasing prevalence of maternal obesity worldwide such that in many populations over half of women enter pregnancy either overweight or obese. This review aims to summarise the impact of maternal obesity on offspring cardiometabolic outcomes. Maternal obesity is associated with increased risk of adverse maternal and pregnancy outcomes. However, beyond this exposure to maternal obesity during development also increases the risk of her offspring developing long-term adverse cardiometabolic outcomes throughout their adult life. Both human studies and those in experimental animal models have shown that maternal obesity can programme increased risk of offspring developing obesity and adipose tissue dysfunction; type 2 diabetes with peripheral insulin resistance and β-cell dysfunction; CVD with impaired cardiac structure and function and hypertension via impaired vascular and kidney function. As female offspring themselves are therefore likely to enter pregnancy with poor cardiometabolic health this can lead to an inter-generational cycle perpetuating the transmission of poor cardiometabolic health across generations. Maternal exercise interventions have the potential to mitigate some of the adverse effects of maternal obesity on offspring health, although further studies into long-term outcomes and how these translate to a clinical context are still required.

Most current nutrition policies and dietary recommendations still reflect decades of research addressing the mechanism of action or health risks of individual nutrients. Yet, most high-income countries including the UK are far from reaching the dietary intakes which are recommended for good health. Food-based dietary patterns (DPs) can help target specific combinations of foods that are associated with disease risk, recognising the coexistence of multiple nutrients within foods and their potential synergistic effects. Reduced rank regression (RRR) has emerged as a useful exploratory approach which uses a priori knowledge of the pathway from diet to disease to help identify DPs which are associated with disease risk in a particular population. Here we reviewed the literature with a focus on longitudinal cohort studies using RRR to derive DPs and reporting associations with non-communicable disease risk. We also illustrated the application of the RRR approach using data from the UK Biobank study, where we derived DPs that explained high variability in a set of nutrient response variables. The main DP was characterised by high intakes of chocolate and confectionery, butter and low-fibre bread, and low intakes of fresh fruit and vegetables and showed particularly strong associations with CVD, type 2 diabetes and all-cause mortality, which is consistent with previous studies that derived ‘Western’ or unhealthy DPs. These recent studies conducted in the UK Biobank population together with evidence from previous cohort studies contribute to the emerging evidence base to underpin food-based dietary advice for non-communicable disease prevention.

Older adults (≥65 years) are the fastest growing population group. Thus, ensuring nutritional well-being of the ‘over-65s’ to optimise health is critically important. Older adults represent a diverse population – some are fit and healthy, others are frail and many live with chronic conditions. Up to 78% of older Irish adults living independently are overweight or obese. The present paper describes how these issues were accommodated into the development of food-based dietary guidelines for older adults living independently in Ireland. Food-based dietary guidelines previously established for the general adult population served as the basis for developing more specific recommendations appropriate for older adults. Published international reports were used to update nutrient intake goals for older adults, and available Irish data on dietary intakes and nutritional status biomarkers were explored from a population-based study (the National Adult Nutrition Survey; NANS) and two longitudinal cohorts: the Trinity-Ulster and Department of Agriculture (TUDA) and the Irish Longitudinal Study on Ageing (TILDA) studies. Nutrients of public health concern were identified for further examination. While most nutrient intake goals were similar to those for the general adult population, other aspects were identified where nutritional concerns of ageing require more specific food-based dietary guidelines. These include, a more protein-dense diet using high-quality protein foods to preserve muscle mass; weight maintenance in overweight or obese older adults with no health issues and, where weight-loss is required, that lean tissue is preserved; the promotion of fortified foods, particularly as a bioavailable source of B vitamins and the need for vitamin D supplementation.

Emotional overeating is a process that is particularly relevant to people within the binge spectrum of eating disorders. Approximately a third of people with overweight share this phenotype. In addition, this behaviour may occur in neurodevelopmental disorders (attention-deficit hyperactivity disorder (ADHD)) and other psychiatric disorders. The biopsychosocial underpinnings of emotional eating include a genetic vulnerability to a higher weight and various cognitive and emotional traits. The environment also plays a key role. For example, the commodification of food and beauty and exposure to weight stigma, unpleasant eating experiences and general adversity can set the scene. The majority of people with binge-eating disorder do not seek treatment (perhaps related to internalised stigma and shame). Hence opportunities for early intervention and secondary prevention are lost. Most guidelines for binge-eating disorder (based on the limited available research) recommend forms of cognitive psychotherapies and antidepressants. However, novel treatments that target underlying mechanisms are in development. These include interventions to improve emotional regulation and inhibitory control using neuromodulation and/or brain training. New technologies have been applied to talking therapies, including apps which can offer ‘just-in-time interventions’ or virtual reality or avatar work which can deliver more personalised interventions using complex scenarios. Drugs used for the treatment of ADHD, psychiatric and metabolic disorders may have the potential to be repurposed for binge-eating disorder. Thus, this is an area of rapid change with novel solutions being applied to this problem.

The aim of this review is to provide an overview of how person-specific interactions between diet and the gut microbiota could play a role in affecting diet-induced weight loss responses. The highly person-specific gut microbiota, which is shaped by our diet, secretes digestive enzymes and molecules that affect digestion in the colon. Therefore, weight loss responses could in part depend on personal colonic fermentation responses, which affect energy extraction of food and production of microbial metabolites, such as short-chain fatty acids (SCFAs), which exert various effects on host metabolism. Colonic fermentation is the net result of the complex interplay between availability of dietary substrates, the functional capacity of the gut microbiome and environmental (abiotic) factors in the gut such as pH and transit time. While animal studies have demonstrated that the gut microbiota can causally affect obesity, causal and mechanistic evidence from human studies is still largely lacking. However, recent human studies have proposed that the baseline gut microbiota composition may predict diet-induced weight loss-responses. In particular, individuals characterised by high relative abundance of Prevotella have been found to lose more weight on diets rich in dietary fibre compared to individuals with low Prevotella abundance. Although harnessing of personal diet–microbiota interactions holds promise for more personalised nutrition and obesity management strategies to improve human health, there is currently insufficient evidence to unequivocally link the gut microbiota and weight loss in human subjects. To move the field forward, a greater understanding of the mechanistic underpinnings of personal diet–microbiota interactions is needed.

Obesity is a major burden on the health system in England and the rest of the UK. Obesity prevalence is high in adults and children and most of the UK population are consuming more energy than required, and not meeting other dietary recommendations, including those for saturated fat, free sugars, fibre, oily fish and fruit and vegetables. Over the past 5 years, a number of cross-government policies, both promoting voluntary action and legislative, have been put in place to tackle diet-related health and obesity. The food environment is complex with many influencing factors, some of which act through individual automatic choices. Other factors such as accessibility, advertising, promotion and nudging drive increased food and drink purchases. With continual changes in the food environment favouring fast-food outlets and meal delivery companies alongside the adverse impact of the COVID-19 pandemic on diets and physical activity levels, further governmental action is likely needed to deliver sustained improvements to diet and health.

The Spring Conference 2021 focused on the theme of the gut microbiome and health that was divided across three separate but inter-related areas from the impact of nutrition on the gut microbiome, the cause and effect of nutrition and health on the gut microbiome to the interaction between pathogens and gut microbiota. The programme was supported by two plenary lectures, the first discussed the computational methods commonly employed to examine gut microbiota and the concluding lecture presented the interaction between the gut microbiome, nutrition and health in older populations. This short report provides a summary and highlights of the conference.

The aim of this review is to summarise the common barriers and motivations for healthy food choice among adolescents, with a specific focus on the Irish context where available. It will also discuss other concerns adolescents have, which may influence their food choices and eating habits. Adolescence represents a period of rapid physical, mental and social development, and many health-related habits developed during adolescence tend to persist into adulthood, making the teenage years an optimal time to encourage healthy eating and health-promoting behaviours. Adolescents are concerned about the health impact of their diet, but their understanding of health is often seen in the context of their physical appearance or body image. Body image concerns are prevalent in adolescents, and this can affect their food choices. Taste, price and convenience are commonly noted factors influencing adolescents' food choices, and as they grow, their level of independence increases and spending more time with their peers means that social desirability and social norms about food become increasingly important factors in adolescent food choice. However, their limited autonomy means their supporting food environment also plays an important role. When developing more targeted interventions in adolescent populations, information on adolescent nutrition needs, their concerns for health and body image, and the barriers and motivations for healthy eating and food choice should be considered. Such a holistic approach should help support healthy eating and the prevention of overweight and obesity in the population, whilst also supporting a healthy relationship with food and their bodies.

Vitamin D intakes and status are low in many countries due to seasonal UVB exposure variation and the fact that few foods are naturally vitamin D rich. Data modelling studies show that vitamin D intakes increase with food fortification, and countries with mandatory fortification policies have higher vitamin D intakes and status compared to countries without. While many foods can be vitamin D fortified, vitamin D bioavailability differs depending on fortification methods, food structure and composition. Randomised controlled trials (RCT) report that vitamin D2 bioavailability varies between foods, whereas vitamin D3 is bioavailable from many foods. In vitro studies suggest that altering the lipid composition of fortified foods increases vitamin D3 absorption. Olive oil increased vitamin D3 absorption during in vitro digestion compared to other dietary oils. Additionally, when vitamin D3 was incorporated into micelles formed from in vitro digestion of olive oil, more vitamin D3 was absorbed compared to other dietary oils. However, in a human postprandial study, a preformed vitamin D3 micelle dairy drink did not increase vitamin D3 absorption, and a vitamin D3 olive dairy drink increased vitamin D3 absorption in vitamin D insufficient participants only. Action is urgently needed to improve vitamin D intakes and status worldwide. Food fortification improves vitamin D intakes; however, fortification strategies unique to each country are needed. This review will synthesise the literature describing data modelling and intervention trials that assess the safety and efficacy of vitamin D fortification strategies, and those manipulating food composition to alter vitamin D bioavailability from fortified foods. Additionally, RCT examining the impact of vitamin D fortification strategies on vitamin D intakes and status over time are reviewed.

In recent years, a wealth of factors are associated with increased risk of developing non-alcoholic fatty liver disease (NAFLD) and NAFLD is now thought to increase the risk of multiple extra-hepatic diseases. The aim of this review is first to focus on the role of ageing and sex as key, poorly understood risk factors in the development and progression of NAFLD. Secondly, we aim to discuss the roles of white adipose tissue (WAT) and intestinal dysfunction, as producers of extra-hepatic factors known to further contribute to the pathogenesis of NAFLD. Finally, we aim to summarise the role of NAFLD as a multi-system disease affecting other organ systems beyond the liver. Both increased age and male sex increase the risk of NAFLD and this may be partly driven by alterations in the distribution and function of WAT. Similarly, changes in gut microbiota composition and intestinal function with ageing and chronic overnutrition are likely to contribute to the development of NAFLD both directly (i.e. by affecting hepatic function) and indirectly via exacerbating WAT dysfunction. Consequently, the presence of NAFLD significantly increases the risk of various extra-hepatic diseases including CVD, type 2 diabetes mellitus, chronic kidney disease and certain extra-hepatic cancers. Thus changes in WAT and intestinal function with ageing and chronic overnutrition contribute to the development of NAFLD – a multi-system disease that subsequently contributes to the development of other chronic cardiometabolic diseases.

The present paper outlines current issues in the nutritional care of women during pregnancy and potential resources to address them. Globally, overnutrition, undernutrition and nutritional imbalances are widespread among women of reproductive age; increasing the risk of pregnancy complications and non-communicable diseases in both mothers and their children. Most women do not meet dietary guidelines for pregnancy. The World Health Organisation (WHO) recommends nutrition and weight counselling during pregnancy for all women. However, clinical practices focusing on nutrition vary and there is no consensus on which outcomes are most important for pregnancy nutrition interventions, with little consideration for the ‘patient voice’. The International Federation of Gynaecology and Obstetrics (FIGO) nutrition checklist is a clinical practice tool that is available for healthcare professionals that will address this issue. The pregnancy nutrition core outcome set will also support advancement of antenatal nutrition by identifying the most critical nutrition-related outcomes from the perspective of healthcare professionals, researchers and women with experience of pregnancy. While poor nutrition can result in adverse outcomes across women of all weight categories, those with obesity may require specialist care to reduce their risk. Obesity is a chronic, progressive, relapsing disease that has high individual variability in its prognosis. The use of obesity staging systems, which consider mental, physical and functional health, can stratify individuals into risk categories and aid in treatment prioritisation in pregnancy. As the prevalence of obesity continues to rise, an obesity staging approach may support clinicians, especially those in limited resource settings.

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.