P Nutr Soc
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Se is an unusual trace element in having its own codon in mRNA that specifies its insertion into selenoproteins as selenocysteine (SeCys), by means of a mechanism requiring a large SeCys-insertion complex. This exacting insertion machinery for selenoprotein production has implications for the Se requirements for cancer prevention. If Se may protect against cancer, an adequate intake of Se is desirable. ⋯ The likelihood of simultaneous and consecutive effects at different cancer stages still allows an important role for anti-cancer Se metabolites such as methyl selenol formed from gamma-glutamyl-selenomethyl-SeCys and selenomethyl-SeCys, components identified in certain plants and Se-enriched yeast that have anti-cancer effects. There is some evidence that Se may affect not only cancer risk but also progression and metastasis. Current primary and secondary prevention trials of Se are underway in the USA, including the Selenium and Vitamin E Cancer Prevention Trial (SELECT) relating to prostate cancer, although a large European trial is still desirable given the likelihood of a stronger effect in populations of lower Se status.
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The prevalence of obesity in the general population is high and it is inevitable that artificial feeding will be needed from time to time in the obese patient, particularly in the critical care setting. Against a background of generous endogenous stores of energy as adipose tissue and the ability of obese individuals to survive starvation longer than non-obese individuals, emphasis is placed on preserving lean body mass and optimizing physiological function. Insulin resistance is typical of the obese individual and is exacerbated by stress; overfeeding is dangerous, particularly if it results in hyperglycaemia. ⋯ Weight may be difficult to measure and lean body mass difficult to assess. Calculation of energy requirements is therefore problematic in practice in the obese individual and there is substantial evidence from controlled clinical trials of the safety of feeding at or below resting energy expenditure. If this approach is taken it is wise to provide a more generous than normal protein intake and to beware of patients with a very high baseline urinary N excretion.
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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. ⋯ 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.
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Review
Nutritional requirements of surgical and critically-ill patients: do we really know what they need?
Malnutrition remains a problem in surgical and critically-ill patients. In surgical patients the incidence of malnutrition ranges from 9 to 44%. Despite this variability there is a consensus that malnutrition worsens during hospital stay. ⋯ Identifying the optimal requirements of ICU patients is far more difficult because of the heterogeneous nature of this population. In general, 5.6 kJ (25 kcal)/kg per d is an acceptable and achievable target intake, but patients with sepsis or trauma may require almost twice as much energy during the acute phase of their illness. The implications of failing to meet and exceeding the requirements of critically-ill patients are also reviewed.
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The ongoing hypermetabolic response in patients with prolonged critical illness leads to the loss of lean tissue mass. Since the cachexia of prolonged illness is usually associated with low concentrations of anabolic hormones, hormonal intervention has been thought to be beneficial. However, most interventions have been shown to be ineffective and their indiscriminate use even causes harm. ⋯ The origin of this suppressed pituitary secretion is located in the hypothalamus, as hypothalamic secretagogues can reactivate the anterior pituitary and restore pulsatile secretion. The reactivated pituitary secretion is accompanied by an increase in peripheral target hormones, indicating at least partial sensitivity of these tissues to anterior pituitary hormones in this chronic phase of illness. Thus, endocrine intervention with a combination of hypothalamic secretagogues that more completely reactivate the anterior pituitary could be a more physiological and effective strategy for inducing anabolism in patients with prolonged critical illness.