European journal of clinical nutrition
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The energy values of carbohydrates continue to be debated. This is because of the use of different energy systems, for example, combustible, digestible, metabolizable, and so on. Furthermore, ingested macronutrients may not be fully available to tissues, and the tissues themselves may not be able fully to oxidize substrates made available to them. ⋯ However, the short-chain carbohydrates, which are also found in breast milk, have little if any laxative role, although do effect the balance of the flora. This latter property has led to the term 'prebiotic', which is defined as the capacity to increase selectively the numbers of bifidobacteria and lactobacilli without growth of other genera. This now well-established physiological property has not so far led through to clear health benefits, but current studies are focused on their potential to prevent diarrhoeal illnesses, improve well-being and immunomodulation, particularly in atopic children and on increased calcium absorption.
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The prevalence of obesity has increased rapidly worldwide and the importance of considering the role of diet in the prevention and treatment of obesity is widely acknowledged. This paper reviews data on the effects of dietary carbohydrates on body fatness. Does the composition of the diet as related to carbohydrates affect the likelihood of passive over-consumption and long-term weight change? In addition, methodological limitations of both observational and experimental studies of dietary composition and body weight are discussed. ⋯ Findings from studies on the effect of the dietary glycemic index on body weight have not been consistent. Dietary fiber is associated with a lesser degree of weight gain in observational studies. Although it is difficult to establish with certainty that fiber rather than other dietary attributes are responsible, whole-grain cereals, vegetables, legumes and fruits seem to be the most appropriate sources of dietary carbohydrate.
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Replacing sugar with low-calorie sweeteners is a common strategy for facilitating weight control. By providing sweet taste without calories, intense sweeteners help lower energy density of beverages and some foods. ⋯ There are recurring arguments that intense sweeteners increase appetite for sweet foods, promote overeating, and may even lead to weight gain. Does reducing energy density of sweet beverages and foods have a measurable impact on appetite and energy intakes, as examined both in short-term studies and over a longer period? Can reductions in dietary energy density achieved with intense sweeteners really affect body weight control? This paper reviews evidence from laboratory, clinical and epidemiological studies in the context of current research on energy density, satiety and the control of food intake.
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A number of reviewers have examined studies investigating the relationship between coronary heart disease and stroke prior to 2000. Since then, several key studies have been published. Five studies have examined the relationship between wholegrain consumption, coronary heart disease (CHD) and cardiovascular (CVD) disease and found protection for either or both diseases. The researchers concluded that a relationship between wholegrain intake and CHD is seen with at least a 20% and perhaps a 40% reduction in risk for those who eat wholegrain food habitually vs those who eat them rarely. Notwithstanding the fact that fibre is an important component of wholegrains, many studies have not shown an independent effect of fibre alone on CHD events. Thus in terms of CHD prevention, fibre is best obtained from wholegrain sources. Wholegrain products have strong antioxidant activity and contain phytoestrogens, but there is insufficient evidence to determine whether this is beneficial in CHD prevention. Soluble fibre clearly lowers cholesterol to a small but significant degree and one would expect that this would reduce CHD events. There have been a small number of epidemiological studies showing soy consumption is associated with lower rates of heart disease. Countering the positive evidence for wholegrain and legume intake has been the Nurses Health Study in 2000 that showed women who were overweight or obese consuming a high glycaemic load (GL) diet doubled their relative risk of CHD compared with those consuming a low GL diet. Although the literature relating GL with CHD events is somewhat mixed, the relationship with risk factors such as HDL cholesterol, triglyceride and C reactive protein is relatively clear. Thus, carbohydrate-rich foods should be wholegrain and, if they are not, then the lowest glycaemic index (GI) product should be used. Promotion of carbohydrate foods should be focused on wholegrain cereals because these have proven to be associated with health benefits. There is insufficient evidence about whether the addition of other components of wholegrains such as polyphenolics or minerals (such as magnesium or zinc) would improve the health benefits of refined grain foods and this needs investigation. Whether adding bran to refined carbohydrate foods can improve the situation is also not clear, and it was found that added bran lowered heart disease risk in men by 30%. This persisted after full adjustment (including GL) suggesting, at least in men, that fibre may be more important than GI. Thus there are two messages: The intake of wholegrain foods clearly protects against heart disease and stroke but the exact mechanism is not clear. Fibre, magnesium, folate and vitamins B6 and vitamin E may be important. The intake of high GI carbohydrates (from both grain and non-grain sources) in large amounts is associated with an increased risk of heart disease in overweight and obese women even when fibre intake is high but this requires further confirmation in normal-weight women. ⋯ Carbohydrate-rich foods should be wholegrain and if they are not, then the lowest GI product available should be consumed. Glycemic index is largely irrelevant for foods that contain small amounts of carbohydrate per serve (such as most vegetables).
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This review examines the evidence for the role of whole grain foods and legumes in the aetiology and management of diabetes. MedLine and SilverPlatter ('Nutrition' and 'Food Science FSTA') databases were searched to identify epidemiological and experimental studies relating to the effects of whole grain foods and legumes on indicators of carbohydrate metabolism. Epidemiological studies strongly support the suggestion that high intakes of whole grain foods protect against the development of type II diabetes mellitus (T2DM). ⋯ Other mechanisms to help explain improvements in glycaemic control when consuming whole grains and legumes relate to cooking, type of starch, satiety and nutrient retention. Thus, there is strong evidence to suggest that eating a variety of whole grain foods and legumes is beneficial in the prevention and management of diabetes. This is compatible with advice from around the world that recommends consumption of a wide range of carbohydrate foods from cereals, vegetables, legumes and fruits both for the general population and for people with diabetes.