Editorial
Editorial
- Mike Forbes
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- Published online by Cambridge University Press:
- 14 December 2007, pp. 201-202
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Research Article
Understanding the nutritional chemistry of lupin (Lupinus spp.) seed to improve livestock production efficiency
- Robert J. van Barneveld
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- Published online by Cambridge University Press:
- 14 December 2007, pp. 203-230
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In their raw, unprocessed form, lupins have many desirable characteristics for feeding both ruminants and single-stomached animals. An emphasis on these desirable characteristics when formulating diets, combined with an advanced knowledge of how components of lupins can influence nutritional value, will ensure they make a cost-effective contribution to livestock diets. The main lupin species used in livestock diets include Lupinus albus, L. angustifolius and L. luteus. Supplementation of ruminant diets with lupins has been shown to have many positive effects in terms of growth and reproductive efficiency, comparable with supplements of cereal grain. The true value of lupins in ruminants, however, can only be determined following a better definition of animal requirements and a closer match of ration specifications. Pigs can effectively utilize L. angustifolius and L. luteus, but detailed research has yet to reveal the reason for poor utilization of diets containing L. albus. Poultry can tolerate high levels of lupins in their diets but levels are often restricted to avoid problems associated with excess moisture in the excreta. Variable responses to enzymes have been observed when attempting to rectify this problem. Lupins have unique carbohydrate properties characterized by negligible levels of starch, high levels of soluble and insoluble NSP, and high levels of raffinose oligosaccharides, all of which can affect the utilization of energy and the digestion of other nutrients in the diet. In addition to carbohydrates, an understanding of lupin protein, lipid and mineral composition together with a knowledge of potential anti-nutritional compounds is required if the use of this legume is to be optimized.
Nutrition and neurodevelopment: mechanisms of developmental dysfunction and disease in later life
- M. J. Dauncey, R. J. Bicknell
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- Published online by Cambridge University Press:
- 14 December 2007, pp. 231-253
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Nutrition plays a central role in linking the fields of developmental neurobiology and cognitive neuroscience. It has a profound impact on the development of brain structure and function and malnutrition can result in developmental dysfunction and disease in later life. A number of diseases, including schizophrenia, may be related to neurodevelopmental insults such as malnutrition, hypoxia, viruses or in utero drug exposure. Some of the most significant findings on nutrition and neurodevelopment during the last three decades, and especially during the last few years, are discussed in this review. Attention is focused on the underlying cellular and molecular mechanisms by which diet exerts its effects. Randomized intervention studies have revealed important effects of early nutrition on later cognitive development, and recent epidemiological findings show that both genetics and environment are risk factors for schizophrenia. Particularly important is the effect of early nutrition on development of the hippocampus, a brain structure important in establishing learning and memory, and hence for cognitive performance. A major aim of future research should be to elucidate the molecular mechanisms underlying nutritionally-induced impairment of neurodevelopment and specifically to determine the mechanisms by which early nutritional experience affects later cognitive performance. Key research objectives should include: (1) increased understanding of mechanisms underlying the normal processes of ageing and neurodegenerative disorders; (2) assessment of the role of susceptibility genes in modulating the effects of early nutrition on neurodevelopment; and (3) development of nutritional and pharmaceutical strategies for preventing and/or ameliorating the adverse effects of early malnutrition on long-term programming.
Nutritional ergogenic aids and exercise performance
- R. J. Maughan
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- Published online by Cambridge University Press:
- 14 December 2007, pp. 255-280
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The use of nutritional supplements in sport is widespread and few serious athletes do not, at some stage in their career, succumb to the temptation to experiment with one or more nutritional supplements. Nutritional ergogenic aids are aimed primarily at enhancing performance (either by affecting energy metabolism or by an effect on the central nervous system), at increasing lean body mass or muscle mass by stimulation of protein synthesis and at reducing body fat content. Although not strictly ergogenic (i.e. capable of enhancing work performance), supplements aimed at increasing resistance to infection and improving general health are seen by athletes as important in reducing the interruptions to training that minor illness and infection can cause. Creatine is perhaps the most widely used supplement in sport at the moment. Supplementation can increase muscle creatine phosphate levels and, although not all published studies show positive results, there is much evidence that performance of short-term high-intensity exercise can be improved by supplementation. Ingestion of large doses of bicarbonate can enhance performance of exercise where metabolic acidosis may be a limiting factor, but there is a significant risk of adverse gastrointestinal side effects. Caffeine can also improve performance, in part by a stimulation of fatty acid mobilization and sparing of the body's limited carbohydrate stores, but also via direct effects on muscle and possibly by central nervous system effects on the perception of effort and fatigue. Carnitine plays an essential role in fatty acid oxidation in muscle but, although supplements are used by athletes, there is no good evidence of a beneficial effect of supplementation. None of these products contravenes the International Olympic Committee regulations on doping in sports, although caffeine is not permitted above a urine concentration of 12 mg/l. Supplementation is particularly prevalent among strength and power athletes, where an increase in muscle mass can benefit performance. Protein supplements have not been shown to be effective except in those rare cases where the dietary protein intake is otherwise inadequate. Individual amino acids, especially ornithine, arginine and glutamine, are also commonly used, but their benefit is not supported by documented evidence. Cr and hydroxymethylbutyrate are also used by strength athletes, but again there are no well-controlled studies to provide evidence of a beneficial effect. Athletes use a wide variety of supplements aimed at improving or maintaining general health and vitamin and mineral supplementation is widespread. There is a theoretical basis, and limited evidence, to support the use of antioxidant vitamins and glutamine during periods of intensive training, but further evidence is required before the use of these supplements can be recommended.
Applying the transtheoretical model to eating behaviour change: challenges and opportunities
- Caroline C. Horwath
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- Published online by Cambridge University Press:
- 14 December 2007, pp. 281-317
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This review provides a rigorous investigation of the question of whether the transtheoretical model (TTM) (or stages of change model) is applicable to eating behaviour change. The TTM is currently the most popular of a number of stage theories being used to examine health behaviour change. Stage theories specify an ordered set of ‘stages of readiness to change’ into which people can be classified and identify the factors that can facilitate movement from one stage to the next. If eating behaviour change follows a stage process, then nutritionists could identify the predominant stage or stages in a population and focus resources on those issues most likely to move people to the next stage (e.g. from no intention of changing, to thinking about changing). In addressing this question, the review draws on the defining characteristics of stage theories as clarified by Weinstein et al. (1998), provides an in-depth coverage of methodological considerations, and a detailed summary table of dietary studies applying the TTM. Specific recommendations are made for improving the accuracy of dietary stage classifications. Among the key conclusions are: (1) dietary studies using the TTM have been hampered by a focus on nutritional outcomes such as dietary fat reduction, rather than clearly understood food behaviours (e.g. five servings of fruit and vegetables per day); (2) accurate stage classification systems are possible for food-based goals, but major misclassification problems occur with nutrient-based goals; (3) observation of an association between stage and dietary intake is not sufficient to demonstrate the validity of the model for dietary behaviour; (4) there is a need for valid questionnaires to measure all aspects of the TTM, and more research on the whole model, particularly the ‘processes of change’, rather than on single constructs such as ‘stage’ (5) cross-sectional studies generally support the predicted patterns of between-stage differences in decisional balance, self-efficacy, and processes of change; (6) studies which test the key hypothesis that different factors are important in distinguishing different stages are rare, as are prospective studies and stage-matched interventions. Only such studies can conclusively determine whether the TTM is applicable to eating behaviour. Since the ultimate test of the TTM will be the effectiveness of stage-matched dietary interventions, the review ends by exploring the requirements for such studies.