P Nutr Soc
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Vegetarian diets do not contain meat, poultry or fish; vegan diets further exclude dairy products and eggs. Vegetarian and vegan diets can vary widely, but the empirical evidence largely relates to the nutritional content and health effects of the average diet of well-educated vegetarians living in Western countries, together with some information on vegetarians in non-Western countries. In general, vegetarian diets provide relatively large amounts of cereals, pulses, nuts, fruits and vegetables. ⋯ Studies of cancer have not shown clear differences in cancer rates between vegetarians and non-vegetarians. More data are needed, particularly on the health of vegans and on the possible impacts on health of low intakes of long-chain n-3 fatty acids and vitamin B(12). Overall, the data suggest that the health of Western vegetarians is good and similar to that of comparable non-vegetarians.
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Coeliac disease is a lifelong intolerance to the gluten found in wheat, barley and rye, and some patients are also sensitive to oats. The disease is genetically determined, with 10% of the first-degree relatives affected and 75% of monozygotic twins being concordant. Of the patients with coeliac disease 95% are human leucocyte antigen (HLA)-DQ2 or HLA-DQ8 positive. ⋯ Patients with minor symptoms, who are found incidentally to have coeliac disease, often ask whether it is necessary to adhere to the diet. Current advice is that dietary adherence is necessary to avoid the long-term complications, which are, principally, osteoporosis and small bowel lymphoma. However, risk of these complications diminishes very considerably in patients who are on a gluten-free diet.
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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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At present the only cure for food allergy is to avoid eating the food responsible for the allergy. Thus, food allergy or food hypersensitivity is a disease that is not only of concern to the individual who is affected but also to those involved directly and indirectly in supplying and preparing food for the food-allergic individual, and its impact on society should be evaluated on this basis. It is generally assumed that questionnaire-based studies vastly overestimate the prevalence of food hypersensitivity. ⋯ The three most-recent prevalence studies on food hypersensitivity (one on perceived food hypersensitivity and two on confirmed food hypersensitivity) all report estimates for prevalence of approximately 3%, but their criteria for including subjects as being positive are not identical, although they do overlap. Furthermore, because of differences in methodology there is no definitive information to indicate whether the prevalence of food allergy is increasing. However, the high prevalence of pollen-related food allergy in younger adults in the population suggests that the increase in pollen allergy is also being accompanied by an increase in pollen-related food allergy.
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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.