The Food Standards Agency undertakes a range of activities with the aim of improving the dietary health of the population and determining how best to communicate key messages to achieve dietary change. Activities include obtaining sound evidence from research and surveys, and seeking advice from independent experts. Work is also undertaken to inform and motivate the population about diet and to identify ways of improving their diet. The effectiveness of the work is monitored in order to inform future policy decisions and interventions and to understand cost implications.

The National Diet and Nutrition Survey (NDNS) of adults aged 19–64 years, carried out in 2000–1, is part of the NDNS programme, a series of cross-sectional surveys aiming to provide detailed quantitative information on the diet, nutritional status and related characteristics of the British population. The programme is split into four surveys of different population age-groups, conducted at approximately three-yearly intervals. In the survey of adults food consumption data were collected from 1724 respondents using a 7 d weighed-intake dietary record. Other components included: height, weight, waist and hip circumference and blood pressure measurements; a 24 h urine sample; a blood sample; a record of physical activity. Results have been published in four volumes covering food consumption, energy and macronutrient intakes, micronutrient intakes and nutritional status, including physical measurements and physical activity. The results have shown that, based on a comparison of nutrient intakes with the UK dietary reference values, adults in Britain are generally getting sufficient nutrients from their diets. However, younger adults (particularly women) and those in lower socio-economic groups are more likely to have low micronutrient intakes and lower levels of some nutritional status indices. The proportion of food energy derived from total fat has fallen since the last survey of this age-group in 1986–7 and is close to the dietary reference value, while the proportion of energy derived from saturated fatty acids and non-milk extrinsic sugars exceeds the dietary reference values. The prevalence of overweight and obesity has increased since 1986–7 and physical activity levels are low.

Dietary Se levels in the UK have fallen over the last 20 years and recent surveys indicate that average Se intakes are 30–40 μg/d, which is well below the current UK reference nutrient intake for adult men (75 μg/d) or women (60 μg/d). Functional consequences of this decline have not been recognised, although epidemiological data suggest it may contribute to increased risk of infections and incidence of some cancers. Previous data have indicated that biochemical changes in Se-dependent proteins occur in otherwise healthy UK subjects given small Se supplements. The current studies have focused on the effect of small Se supplements on the immune response since there is evidence of specific interactions between Se intake and viral replication, and since the potential anti-cancer effects of Se may be mediated by non-antioxidant effects of Se such as changes in immune function. Data indicate that subjects given small Se supplements (50 or 100 μg Se/d) have changes in the activity of Se-dependent enzymes and evidence of improved immune function and clearance of an administered live attenuated virus in the form of poliovirus vaccine. Responses of individual subjects to Se supplements are variable, and current work is evaluating potential explanations for this variability, including genetic variability and pre-existing Se status.

Fe homeostasis is considered in the context of the UK diet, using information on Fe intake and status from the National Diet and Nutrition Surveys. The importance of assessing Fe availability rather than total Fe intake is discussed. Dietary and host-related factors that determine Fe bioavailability (Fe utilised for Hb production) are reviewed using information from single-meal studies. When adaptive responses are taken into consideration, foods associated with higher Fe status include meat (haem-Fe and the ‘meat factor’) and fruits and fruit juice (vitamin C). Foods that may have a negative impact include dairy products (Ca), high-fibre foods (phytate) and tea and coffee (polyphenols), but the effects are more apparent in groups with marginal Fe deficiency, such as women of childbearing age. Analysis of dietary intake data on a meal-by-meal basis is needed to predict the influence of changing dietary patterns on Fe nutrition in the UK. Current information suggests that in the UK Fe deficiency is a greater problem than Fe overload.

The achievement of optimal folate status to prevent neural-tube defects, and possibly other diseases, is hindered by the well-recognised incomplete bioavailability of the natural folates found in foods compared with the synthetic vitamin, folic acid. Folate bioavailability from different foods is considered to be dependent on a number of factors, including the food matrix, the intestinal deconjugation of polyglutamyl folates, the instability of certain labile folates during digestion and the presence of certain dietary constituents that may enhance folate stability during digestion. There is conflicting evidence as to whether the extent of conjugation of polyglutamyl folate (in the absence of specific inhibitors of deconjugation in certain foods) is a limiting factor in folate bioavailability. Estimates of the extent of lower bioavailability of food folates compared with folic acid (relative bioavailability) show great variation, ranging anywhere between 10 and 98%, depending on the methodological approach used. The lack of accurate data on folate bioavailability from natural food sources is of particular concern in those countries in which there is no mandatory folic acid fortification, and therefore a greater reliance on natural food folates as a means to optimise status. Apart from the incomplete bioavailability of food folates, the poor stability of folates in foods (particularly green vegetables) under typical conditions of cooking can substantially reduce the amount of vitamin ingested and thereby be an additional factor limiting the ability of food folates to enhance folate status. A recent workshop convened by the Food Standards Agency concluded that gaining a better understanding of folate bioavailability in representative human diets is a high priority for future research.

A world epidemic of diet-related chronic disease is currently being faced. In the UK incidence of obesity alone has tripled in the last 20 years and this trend is predicted to continue. Consensus exists for the urgent need for a change in diet and other lifestyle factors and for the direction and targets for this change. The evidence for how this change can be achieved is less certain. It has been established that disease processes begin in childhood. Recent evidence indicates that dietary habits too are established in childhood but that these habits are amenable to change. While establishing a healthy lifestyle in childhood is paramount, interventions have the potential to promote positive change throughout the life course. Success in reversing current trends in diet-related disease will depend on commitment from legislators, health professionals, industry and individuals, and this collaboration must seek to address not only the food choices of the individual but also the environment that influences such choices. Recent public health policy development in England, if fully supported and implemented, is a positive move towards this goal. Evidence for effective strategies to promote dietary change at the individual level is emerging and three reviews of this evidence are discussed. In addition, three recent dietary intervention studies, in three different settings and with different methods and aims, are presented to illustrate methods of effecting dietary change. Further work is required on what factors influence the eating behaviour and physical activity of individuals. There is a need for further theory-based research on which to develop more effective strategies to enable individuals to adopt healthier lifestyles.

During this workshop, held as part of a joint Nutrition Society and Food Standards Agency (Agency) meeting on Micronutrient interactions and public health, several precepts for a successful funding application to the Agency were discussed. These precepts, many of which can be used as guiding principles for project proposals to other funding bodies, are summarised as follows: remember that the Agency only supports research that will help them formulate or change human food policy; read the research requirements document thoroughly and plan your project to answer the call; remember that the Agency issues contracts, not grants; your project will be just one project within a focused and coordinated programme; collaborative work is encouraged, but this type of approach is not a licence to double or treble your costs; write a one-page executive summary and attach it to the front of the form; the statistical basis for your experimental design and proposed statistical analysis of your results are important criteria in the evaluation of your proposal; your plans for dissemination and exploitation are very important; match your project duration against your research plan; abide by the Agency plan for quality assurance for the management of research; make full use of the programme adviser and the Agency policy contact and the ‘feedback’ stage to refine your scientific ideas in line with Agency policy.

Pregnancy is a period of rapid growth and cell differentiation for both the mother and fetus. Consequently, it is a period when both are vulnerable to changes in dietary supply, especially of those nutrients that are marginal under normal circumstances. In developed countries this vulnerability applies mainly to micronutrients. Even now, Fe deficiency is a common disorder, especially in pregnancy. Similarly, Cu intake in the UK population is rarely above adequate levels, which is a matter of some concern, both in terms of public health and possible clinical consequences. In early studies it was shown that lambs born to mothers on Cu-deficient pastures develop ‘swayback,’ with neurological and muscular symptoms that cannot be reversed by postnatal supplementation. More recently, rat studies have shown that responses such as the ‘startle’ response are lost in offspring of Cu-deficient mothers. Data have shown that prenatal Fe deficiency results in increased postnatal blood pressure, even though the offspring have normal dietary Fe levels from birth. These observations emphasise the importance of Fe and Cu in growth and development. In the present review the importance of these metals and the consequences, both short term and long term, of deficiency will be discussed and some possible mechanisms whereby these effects may be generated will be considered.

The intimate relationship between Fe and Cu in human nutrition has been recognised for many years. The best-characterised link is provided by caeruloplasmin, a multiCu-binding protein that acts as a serum ferrioxidase and is essential for the mobilisation of Fe from storage tissues. Decreased Cu status has been shown to reduce holo-caeruloplasmin production and impair ferrioxidase activity, leading, in a number of cases, to decreased tissue Fe release and the generation of anaemia that is responsive to dietary supplementation with Cu but not Fe. Dietary Fe absorption also requires the presence of a multiCu ferrioxidase. Hephaestin, a caeruloplasmin homologue, works in concert with the IREG1 transporter to permit Fe efflux from enterocytes for loading onto transferrin. The essential role of hephaestin in this process has been recognised from studies in the sex-linked anaemic (sla) mouse, in which Fe efflux is markedly impaired as a result of a mutation in the hephaestin gene that results in a truncated and non-functional version of the protein. There is emerging evidence that a number of other components of the intestinal Fe transport pathway are also Cu sensitive. Divalent metal transporter 1 (DMT1), the Fe transporter located at the apical membrane of enterocytes, is also a physiologically-relevant Cu transporter, suggesting that these two metals may compete with each other for uptake into the duodenal enterocytes. Furthermore, expression of both DMT1 and the basolateral Fe-efflux transporter IREG1 can be regulated by Cu, suggesting that the Fe–Cu relationship may be more complex than first thought.

Lower levels of dietary folate are associated with the development of epithelial cell tumours in man, particularly colo-rectal cancer. In the majority of epidemiological studies blood folate or reported folate intake have been shown to be inversely related to colo-rectal cancer risk. Folate, via its pivotal role in C1 metabolism, is crucial both for DNA synthesis and repair, and for DNA methylation. This function is compromised when vitamin B12 is low. Vitamin B12 deficiency has been shown to increase biomarkers of DNA damage in man but there is no evidence directly linkinglow vitamin B12 with cancer. Disturbingly, folate and vitamin B12 deficiencies are common in the general population, particularly in the underprivileged and the elderly. How folate and/or vitamin B12 deficiency influence carcinogenesis remains to be established, but it is currently believed that they may act to decrease DNA methylation, resulting in proto-oncogene activation, and/or to induce instabilityin the DNA molecule via a futile cycle of uracil misincorporation and removal. The relative importance of these two pathways may become clear by determining both DNA stability and cytosine methylation in individuals with different polymorphic variants of key folate-metabolising enzymes. 5,10-Methylenetetrahydrofolate reductase converts 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate and thereby controls whether folate is employed for DNA synthesis or DNA methylation. Colo-rectal cancer risk is decreased in subjects homozygous for a common variant (C677T) of the gene coding for this enzyme, suggesting that DNA synthesis and repair may be ‘enhanced’ in these individuals. Evidence from animal and human studies is presented here in support of folate acting to maintain genomic stability through both these mechanisms.

Air is one of our most important natural resources; however, it is also in the front line for receiving environmental pollution. Air quality decreased markedly following the industrial revolution, but it was not until the great London Smog in 1952 that air quality made it onto the political agenda. The introduction of the Clean Air Act in 1956 led to dramatic decreases in black smoke and SO2 concentrations over the next two decades, as domestic and industrial coal-burning activities ceased. However, as these improvements progressed, a new threat to public health was being released into the air in ever-increasing quantities. Rapid motorisation of society from the 1960s onwards has led to the increased release of atmospheric pollutants such as tiny particles (particulate matter of &10 μm in aerodynamic diameter) and oxides of N, and the generation of the secondary pollutant O3. These primary and secondary traffic-related pollutants have all proved to be major risks factors to public health. Recently, oxidative stress has been identified as a unifying feature underlying the toxic actions of these pollutants. Fortunately, the surface of the lung is covered with a thin layer of fluid containing a range of antioxidants that appear to provide the first line of defence against oxidant pollutants. As diet is the only source of antioxidant micronutrients, a plausible link now exists between the sensitivity to air pollution and the quality of the food eaten. However, many questions remain unanswered in relation to inter-individual sensitivity to ambient air pollution, and extent to which this sensitivity is modified by airway antioxidant defences.

Adverse dietary factors account for approximately 30% of all cancers. Overconsumption of energy is undoubtedly one of the major risk factors, but dietary composition is also very important. In particular, a low consumption of fruits and vegetables appears to double the risk of carcinomas of the lung and alimentary tract. Epidemiological studies suggest that high plasma levels of Se, carotenoids and ascorbic acid are protective against cancer. However, intervention studies with antioxidant nutrients have given mixed results, and it has not been established that the benefits of a high intake of fruits and vegetables are invariably related to the prevention of oxidative DNA damage. Folic acid supplementation appears to protect against colo-rectal neoplasia, probably by preventing mutations associated with the repair of uracil mis-incorporation. However, there are indications from animal studies that exposure to high levels of folic acid at certain stages of development may lead to epigenetic effects that are, as yet, poorly understood. There seems little doubt that micronutrients contribute to the protective effects of plant foods against cancers of the lung and alimentary tract, but it has not been established that these benefits can be achieved using supplements.

The present review focuses on the B-vitamins, i.e. folate, vitamin B12, vitamin B6 and riboflavin, that are involved in homocysteine metabolism. Homocysteine is a S-containing amino acid and its plasma concentrations can be raised by various constitutive, genetic and lifestyle factors, by inadequate nutrient status and as a result of systemic disease and various drugs. Hyperhomocysteinaemia is a modest independent predictor of CVD and stroke, but causality and the precise pathophysiological mechanism(s) of homocysteine action remain unproven. The predominant nutritional cause of raised plasma homocysteine in most healthy populations is folate insufficiency. Vitamin B12 and, to a lesser extent, vitamin B6 are also effective at lowering plasma homocysteine, especially after homocysteine lowering by folic acid in those individuals presenting with raised plasma homocysteine. However, riboflavin supplementation appears to be effective at lowering plasma homocysteine only in those individuals homozygous for the T allele of the C677 T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene. This gene codes for the MTHFR enzyme that produces methyltetrahydrofolate, which, in turn, is a substrate for the remethylation of homocysteine by the vitamin B12-dependent enzyme methionine synthase. Individuals with the MTHFR 677 TT genotype are genetically predisposed to elevated plasma homocysteine, and in most populations have a markedly higher risk of CVD.

Micronutrient malnutrition is widespread throughout the world, with important health and economic consequences. Tools to address this situation include food fortification, supplementation and dietary diversification, each having different and complementary roles. Fortification (mandatory and voluntary) has been practised over several decades in Western countries as well as in developing countries. Iodised salt was introduced in the USA in 1924 to reduce severe I deficiency. In 1938 voluntary enrichment of flours and breads with niacin and Fe was initiated to reduce the incidence of pellagra and Fe-deficiency anaemia respectively. Micronutrient intakes in European countries appear to be generally adequate for most nutrients. However, a number of population subgroups are at higher risk of suboptimal intakes (below the lower reference nutrient intake) for some micronutrients, e.g. folate, Fe, Zn and Ca in children, adolescents and young women. Dietary surveys indicate that fortified foods play a role in mitigating such risks for several important nutrients. The number of foods suited to fortification are considerably limited by several factors, including technological properties (notably moisture, pH and O2 permeability), leading to unacceptable taste and appearance, as well as cost and consumer expectations. In countries in which voluntary fortification is widely practised micronutrient intakes are considerably below tolerable upper intake levels. Concerns about safety are addressed in relation to the potentially increased level or proportion of fortified foods (e.g. following potential EU legislation), for nutrients with relatively low tolerable upper intake levels and where the potential benefit and risks are in different subpopulations (e.g. folic acid). Recent models for assessing these issues are discussed.

Diet and lifestyle advice for individuals with diabetes has changed dramatically. The changes in nutritional recommendations have largely been in response to advances in the knowledge of the biochemical and physiological mechanisms of impaired glucose metabolism and the micro- and macrovascular complications of diabetes. The most recent guidelines for the nutritional management of diabetes were set out by Diabetes UK in 2003. This consensus-based advice paper builds on the previous evidence-based review papers of the European Association for the Study of Diabetes in 2000 and the American Diabetes Association in 2002. The changes from previous recommendations include a more liberal use of sucrose, in line with healthy eating recommendations for the general population, and allow for greater flexibility in energy derived from carbohydrate and monounsaturated fat. In addition, monounsaturated fats are promoted as the fat of choice and active promotion of carbohydrate foods with a low glycaemic index is encouraged. These guidelines emphasise the practical application of nutritional management of diabetes and the need to provide education and support in a structured way that will facilitate change in diet and lifestyle behaviour. Structured educational programmes have been shown to be effective in reducing the progression to diabetes and also in slowing the onset and progression of the complications of diabetes. These programmes require ongoing intensive input to maintain behavioural change in diet and lifestyle. Considerable energy and resources are required to set up and maintain these educational programmes, but the cost per individual is small compared with the costs of treating the complications of diabetes.

Increasing awareness of hazards associated with the use of antibiotic and chemical feed additives has accelerated investigations into plants and their extracts as feed additives. The present review mainly discusses two classes of plant secondary compounds in this context, i.e. essential oils and saponins. The broader potential of plants and their extracts is illustrated by the progress of an EC Framework 5 project, ‘Rumen-up’. Dietary inclusion of a commercial blend of essential oils causes markedly decreased NH3 production from amino acids in rumen fluid taken from sheep and cattle. This effect is mediated partly by the effects on hyper-NH3-producing bacteria and the protein- and starch-fermenting rumen bacterium, Ruminobacter amylophilus. Saponin-containing plants and their extracts suppress the bacteriolytic activity of rumen ciliate protozoa and thereby enhance total microbial protein flow from the rumen. The effects of some saponins are transient, because saponins are hydrolysed by bacteria to their corresponding sapogenin aglycones, which are much less toxic to protozoa. Saponins also have selective antibacterial effects that may prove useful in, for example, controlling starch digestion. The ‘Rumen-up’ project began with a targetted collection of European plants and their extracts, which partners have tested for their effects on rumen proteolysis, protozoa, methanogenesis and lactate production. A success rate of about 5% in terms of positive hits illustrates that plant secondary compounds, of which essential oils and saponins comprise a small proportion, have great potential as ‘natural’ manipulators of rumen fermentation to benefit the farmer and the environment in the future.

The purported antiparasitic properties of plant secondary metabolites (PSM) have been the cause of controversy amongst the scientific community. Despite long-standing knowledge of the prophylactic and therapeutic properties of PSM-rich extracts, which comes mainly from ethnoveterinary sources, the scientific evidence of the antiparasitic effects of PSM is inconsistent. In the first part of the present paper the causes of this controversy are addressed, and the evidence available on the antiparasitic effects of PSM is critically examined. The focus is on examples of the antiparasitic activity of PSM against helminth nematodes. The conclusion is that PSM can have antiparasitic properties, which depend on their structure, level of ingestion and availability within the gastrointestinal tract of the animal. The second part is an appraisal of the potential role of PSM for parasite control in ruminant production systems. Despite their antiparasitic properties, PSM consumption does not necessarily have positive consequences in parasitised herbivores, as excessive consumption of PSM can adversely affect herbivore fitness and survival, through their anti-nutritional properties. For this reason it is suggested that the antiparasitic properties of PSM should be assessed at the same time as their anti-nutritional effects. The same measure, e.g. the performance of parasitised hosts, should be used when assessing these properties. The assessment of the costs and benefits suggests that parasitised herbivores can benefit from the long-term consumption of PSM only if the antiparasitic benefits outweigh the anti-nutritional costs of PSM. In addition, it is proposed that parasitised animals might be able to benefit from PSM consumption even if their performance is impaired, as long as the latter is a short-term compromise that leads to long-term benefits.

The present paper provides an overview of the methodological principles that underpinqualitative research and how these principles differ from those of quantitative research. It is intended to set the scene for the following papers that outline two specific approaches to the analysis of qualitative data. Within the tradition of qualitative research there are many different theoretical perspectives, of which these approaches are only two examples, but they need to be set within this broader tradition in order to highlight their specific features. Qualitative and quantitative research differ from each other in far more than their methods and data. They are each based on very different premises about both the nature of the world and the nature of our knowledge of it and how this information is generated. These approaches have implications for all aspects of research strategy, including the assessment of the quality of research findings and their wider utility or application. In relation to the latter, lack of detail in the reporting of qualitative research and small sample sizes has tended to create the impression that the findings of qualitative research have little application outside the particular research setting. While there is need for more rigor in reporting, it needs to be recognized that qualitative research can offer insights and understandings with wider relevance, althoughthese outcomes are of a different type from those provided by quantitative research.

The present paper introduces interpretative phenomenological analysis (IPA) as a framework for analysing qualitative research data collected for public health nutrition and dietetic research studies. The theoretical roots of IPA have been set out briefly in order to help researchers decide whether the approach is relevant for them and their particular research questions. IPA can be used to analyse data from one-to-one interviews in order to develop ‘thick descriptions’ that may help illuminate human experience. IPA can also be used to develop theories and/or models, which could help inform policy. The main body of the paper describes the analytical techniques and procedures used to achieve both outcomes in a practical way, using examples from the author's own research. In the following paper Krueger's methods for analysing focus group data are set out for comparison. It is hoped that these papers will empower researchers with little experience of qualitative research to develop confidence with qualitative data analysis. In addition, it is hoped that the material will stimulate debate amongst more experienced qualitative researchers from a public health or dietetic background.

In recent years focus-group interviews, as a means of qualitative data collection, have gained popularity amongst professionals within the health and social care arena. Despite this popularity, analysing qualitative data, particularly focus-group interviews, poses a challenge to most practitioner researchers. The present paper responds to the needs expressed by public health nutritionists, community dietitians and health development specialists following two training sessions organised collaboratively by the Health Development Agency, the Nutrition Society and the British Dietetic Association in 2003. The focus of the present paper is on the concepts and application of framework analysis, especially the use of Krueger's framework. It provides some practical steps for the analysis of individual data, as well as focus-group data using examples from the author's own research, in such a way as to assist the newcomer to qualitative research to engage with the methodology. Thus, it complements the papers by Draper (2004) and Fade (2004) that discuss in detail the complementary role of qualitative data in researching human behaviours, feelings and attitudes. Draper (2004) has provided theoretical and philosophical bases for qualitative data analysis. Fade (2004) has described interpretative phenomenology analysis as a method of analysing individual interview data. The present paper, using framework analysis concentrating on focus-group interviews, provides another approach to qualitative data analysis.