Inequalities in diet and nutrition

The inequality of nutrition and obesity re-focuses concern on who in society is consuming the worst diet. Identification of individuals with the worst of dietary habits permits for targeting interventions to assuage obesity among the population segment where it is most prevalent. We argue that the use of fiscal interventions does not appropriately take into account the economic, social and health circumstances of the intended beneficiaries of the policy. This paper reviews the influence of socio-demographic factors on nutrition and health status and considers the impacts of nutrition policy across the population drawing on methodologies from both public health and welfare economics. The effects of a fat tax on diet are found to be small and while other studies show that fat taxes saves lives, we show that average levels of disease risk do not change much: those consuming particularly bad diets continue to do so. Our results also suggest that the regressivity of the policy increases as the tax becomes focused on products with high saturated fat contents. A fiscally neutral policy that combines the fat tax with a subsidy on fruit and vegetables is actually more regressive because consumption of these foods tends to be concentrated in socially undeserving households. We argue that when inequality is of concern, population-based measures must reflect this and approaches that target vulnerable populations which have a shared propensity to adopt unhealthy behaviours are appropriate.

Diet and lifestyle in Bronze Age Northwest Spain: the collective burial of Cova do Santo

A multidisciplinary investigation of the collective burial of Cova do Santo is presented as a novel approach to understand daily life during the Bronze Age in Northwest Iberia. The research is focused on three main aspects: i) taphonomy and patterns of disposal, ii) paleopathology and -demography as indicators of health status and lifestyle, and iii) stable isotope analysis to reconstruct paleodiet and to investigate the timing of the introduction of millet to the Iberian Peninsula. Osteological analyses were performed on 64 bones (61 human and 3 animal); additionally, bone collagen was extracted from 15 samples (13 human and 2 animal) and analyzed for its carbon and nitrogen stable isotopes composition. The radiocarbon age of the human remains is consistent with the Middle Bronze Age (c. 1890 to 1600 cal BC). The recovered remains belonged to a minimum number of 14 individuals with an estimated age at death of forty years or younger. This relatively young age is in contrast to a high prevalence of degenerative joint disease in the group. The isotopic results suggest a very homogeneous diet, which was almost exclusively based on C3 plants and terrestrial animal products. Overall, the data suggest that the studied population belonged to a period prior to the introduction of spring or summer-grown crops such as millets. The collective burial from the cave of Cova de Santo, Galicia, currently represents the largest assemblage of prehistoric human remains from Northwest Spain and the relatively good preservation of the bones offers a unique opportunity to investigate daily life in Northern Iberia during the Bronze Age.

Diet and herding strategies in a changing environment: stable isotope analysis of Bronze Age and Late Antique skeletal remains from Ya'amūn, Jordan

Carbon and nitrogen stable isotope ratios of 45 human and 23 faunal bone collagen samples were measured to study human diet and the management of domestic herbivores in past Jordan, contrasting skeletal remains from the Middle and Late Bronze Age and the Late Roman and Byzantine periods from the site of Ya'amūn near Irbid. The isotope data demonstrate that the management of the sheep and goats changed over time, with the earlier animals consuming more plants from semi-arid habitats, possibly because of transhumant herding strategies. The isotope data for fish presented here are the first from archaeological contexts from the Southern Levant. Although fish of diverse provenance was available at the site, human diet was predominately based on terrestrial resources and there was little dietary variability within each time-period. Isotopic variation between humans from different time-periods can mostly be explained by ‘baseline shifts’ in the available food sources; however, it is suggested that legumes may have played a more significant role in Middle and Late Bronze Age diet than later on.

British Nutrition Foundation annual lecture: chips with everything? Nutritional genomics and the application of diet in disease prevention

The development of high throughput techniques ('chip' technology) for measurement of gene expression and gene polymorphisms (genomics), and techniques for measuring global protein expression (proteomics) and metabolite profile (metabolomics) are revolutionising life science research, including research in human nutrition. In particular, the ability to undertake large-scale genotyping and to identify gene polymorphisms that determine risk of chronic disease (candidate genes) could enable definition of an individual's risk at an early age. However, the search for candidate genes has proven to be more complex, and their identification more elusive, than previously thought. This is largely due to the fact that much of the variability in risk results from interactions between the genome and environmental exposures. Whilst the former is now very well defined via the Human Genome Project, the latter (e.g. diet, toxins, physical activity) are poorly characterised, resulting in inability to account for their confounding effects in most large-scale candidate gene studies. The polygenic nature of most chronic diseases offers further complexity, requiring very large studies to disentangle relatively weak impacts of large numbers of potential 'risk' genes. The efficacy of diet as a preventative strategy could also be considerably increased by better information concerning gene polymorphisms that determine variability in responsiveness to specific diet and nutrient changes. Much of the limited available data are based on retrospective genotyping using stored samples from previously conducted intervention trials. Prospective studies are now needed to provide data that can be used as the basis for provision of individualised dietary advice and development of food products that optimise disease prevention. Application of the new technologies in nutrition research offers considerable potential for development of new knowledge and could greatly advance the role of diet as a preventative disease strategy in the 21st century. Given the potential economic and social benefits offered, funding for research in this area needs greater recognition, and a stronger strategic focus, than is presently the case. Application of genomics in human health offers considerable ethical and societal as well as scientific challenges. Economic determinants of health care provision are more likely to resolve such issues than scientific developments or altruistic concerns for human health.

Apparent digestibility and nitrogen utilisation of diets based on maize and grass silage fed to beef steers

Substituting grass silage with maize silage in forage mixtures may result in one forage influencing the nutritive value of another in terms of whole tract nutrient digestibility and N utilisation. This experiment investigated effects of four forage combinations being, grass silage (G); 67 g/100 g grass silage + 33 g/100 g maize silage (GGM); 67 g/100 g maize silage + 33 g/100 g grass silage (MMG); maize silage (M). All diets were formulated to be isonitrogenous (22.4 g N/kg dry matter [DM]) using a concentrate mixture. Ration digestibility and N balance was determined using 7 Holstein Friesian steers (mean body weight 411.0 +/- 120.9 kg) in a cross-over design. Inclusion of maize silage in the diet had a positive linear effect on forage and total DM intake (P = 0.001), and on apparent DM and organic matter digestibility (both P = 0.048). Regardless of the silage ratio used, the metabolisable energy concentration of maize silage was calculated to be higher than that of grass silage (P = 0.058), and linearly related to the relative proportions of the two silages in the forage mixture. Inclusion of maize silage in the diet resulted in a linear decline in the apparent digestibility of starch (P = 0.022), neutral detergent fibre (P < 0.001) and acid detergent fibre (P = 0.003). Nitrogen retention, expressed as amount retained per day or in terms of body weight (g/100 kg) increased linearly with maize inclusion (P = 0.047 and 0.046, respectively). Replacing grass silage with maize silage caused linear responses according to the proportions of each forage in the diet, and that there were no associative effects of combining forages. (C) 2004 Elsevier B.V. All rights reserved.

Nutrition of chicks and layers

When formulating least-cost poultry diets, ME concentration should be optimised by an iterative procedure, not entered as a fixed value. This iteration must calculate profit margins by taking into account the way in which feed intake and saleable outputs vary with ME concentration. In the case of broilers, adjustment of critical amino acid contents in direct proportion to ME concentration does not result in birds of equal fatness. To avoid an increase in fat deposition at higher energy levels, it is proposed that amino acid specifications should be adjusted in proportion to changes in the net energy supplied by the feed. A model is available which will both interpret responses to amino acids in laying trials and give economically optimal estimates of amino acid inputs for practical feed formulation. Flocks coming into lay and flocks nearing the end of the pullet year have bimodal distributions of rates of lay, with the result that calculations of requirement based on mean output will underestimate the optimal amino acid input for the flock. Chick diets containing surplus protein can lead to impaired utilisation of the first-limiting amino acid. This difficulty can be avoided by stating amino acid requirements as a proportion of the protein.