Progress in food & nutrition science最新文献

Cholesterol under certain in vitro and possibly in vivo conditions may be oxidized to oxysterols, which are suspected of being initiators of atherosclerotic plaques. Oxysterols inhibit HMG-CoA reductase activity resulting in a decreased cholesterol concentration in the cell membrane, which leads to endothelial membrane injury and probable premature cell death. Exogenous oxidation of cholesterol in human tissues under certain unusual conditions is highly probable. Dietary oxysterols are absorbed in the gastrointestinal tract and are selectively transported by the athrogenic lipoproteins LDL and VLDL. The oxysterols cholestanetriol and 25-OH cholesterol have been shown to be atherogenic. Oxysterols are commonly found in dried egg products, powdered milk, cheeses and in a variety of high temperature dried animal products.

Trace elements occur in the body in very small or 'trace' amounts. Deficiencies of essential trace elements produce multiple and diverse clinical signs and symptoms. These may arise from inadequate dietary intake, decreased bioavailability, iatrogenic factors, certain disease states in which decreased absorption, excessive excretion and/or utilization occurs, and physiological states in which trace element requirements are increased and/or body stores are reduced. This review discusses both the static and functional laboratory tests used for the assessment of chromium, copper, selenium, and zinc status in humans, with emphasis on those tests suitable for community use. Static tests measure the total quantity of the trace elements in various accessible tissues and body fluids such as hair, nails, blood or some of its components, and urine; functional tests measure the activity of trace-element-dependent enzymes, or a physiological or behavioural function dependent on a specific trace element. The advantages and limitations of each test are discussed, together with the effects of non-nutritional factors that may confound the interpretation of the results. Interpretive criteria are also given, where possible.

Inclusion of raw soyabean in diets considerably inhibits the growth of young animals. This is due to interference with normal gut and systemic metabolism, particularly of pancreas, liver and muscle. Pancreatic hypertrophy and hyperplasia occur in the young of a number of species given soyabean. In the rat, this enlargement, which is primarily a result of interference with CCK-mediated feedback control of exocrine pancreatic secretion, persists upon prolonged feeding and leads to a susceptibility of the pancreas to carcinogens and an increased incidence of neoplasia. In contrast, with pigs or dogs, in which feedback regulation is primarily mediated via secretin, no increase in pancreas enlargement results from consumption of soyabean. Dietary soyabean or trypsin inhibitors do however alter pancreatic secretion in humans. It is at present unclear how this response is mediated. The growth inhibition and interference with intestinal and systemic metabolism observed upon soyabean feeding is due to the presence of trypsin inhibitors, lectin and anti-nutritional factors, devoid of trypsin inhibitory or lectin activity, in the seed meal. The effects of these dietary factors are additive and possibly synergistic. Most of the anti-nutritional effects of soyabean can be abolished by proper aqueous heart-treatment. However, with a proportion of calves, pigs, lambs and humans even heat-treated soyabean has deleterious effects. These can only be eliminated by hot aqueous-ethanol extraction of the meal.

Public interest in the health benefits of seafood lipids, or of fish oils, is a most unusual phenomenon because for once the recommendations of health authorities to "eat more fish" are in accord with newer and popular attitudes. Media exploitation of the more sensational health aspects is also generally in favor of more consumption of seafood. The public is however still confused by the multitude of species of fish and shellfish available, and in a quandary over whether fatty fish are risky in terms of calories or cholesterol, or of more benefit than lean fish in terms of omega-3 fatty acids. Most direct questions on how much omega-3 fatty acids are useful in the diet of an average individual may never be answerable until long term studies with humans are carried out. It does appear that marine fish can be broken down into four convenient categories: lean (including shellfish), low fat, medium fat and high fat; and in this review it is suggested that these could contribute, per 100 grams, respectively about 250, 750, 1000 and 2000 mg of total C20 + C22 omega-3 fatty acids. This intake can compare favorably with the alternative of commonly available fish oil capsules. Moreover this survey shows that at present the composite of total omega-3 fatty acids in fish and shellfish may contain roughly equal proportions of the functionally effective eicosapentaenoic acid, and of docosahexaenoic acid with its as yet unknown long-term biochemical effects, or be biased in favor of more of the latter. To assist the public, nutritionists, dietitians, and researchers this review discusses the distribution of fat in edible fish muscle, the classes of lipids encountered, and the major fatty acids of health interest. Included are limited numbers of analyses from parts of the world other than North America.

Obesity is a widespread condition, with different etiologies, that is usually treated only symptomatically i.e. through lowered energy intake. The existence of a latent situation of pre-obesity is postulated. The preobese is defined as a lean individual susceptible to easily develop obesity with unlimited food availability. The physiologic and metabolic pathways responsible of the appearance of obesity are revisited, as well as the current theories on body weight regulatory mechanisms. From this information, a classification of obesities is proposed: 1) Hypothalamic, 2) Bulimic, 3) Digestive, 4) Hyperinsulinemic, 5) Hypothermogenic, 6) Hypothyroid, and 7) Set point. These conditions should not be treated therapeutically in the same way, as the causes of development of the illness are not equal. The need to determine the individualized causes of obesity prior to any treatment is stressed.

Developing countries face the problem of an increasing fuelwood shortage. For rural households, fuelwood is the main source of energy. As energy is essential to make food suitable for human consumption by means of cooking, the present fuelwood crisis could jeopardize the nutritional situation of rural households. This article reviews and analyses available data and information on the relationship between the availability of fuelwood and the nutritional situation of rural households. Based on analysis of emperical studies, three main strategies evolved by rural households, especially by the women within these households, to cope with a shortage of fuelwood can be distinguished: (i) increase in time and energy spent on fuelwood collection, (ii) substitution of fuelwood by alternative fuels and (iii) economizing on the consumption of fuelwood and alternative fuels. These coping-strategies affect food supply, food preservation, preparation and distribution, income generating activities and food consumption, all of which result in a decrease in quality and quantity of food consumed and in a deterioration of physical condition, especially women and their young children. Available data on fuelwood availability and nutrition are rather diffuse and incomplete. The presence of several confounding variables in the studies analysed make it difficult to establish the nutritional impact of a growing shortage of fuelwood. Nevertheless, it is concluded that a shortage of fuelwood plays at least an important role in changes in nutritional situation of rural households. If current trends continue, this role will become more important and evident. The impact of a growing fuelwood shortage should be a point of concern for rural development.

Due to the importance of diet in the management of noninsulin dependent diabetes, we are interested in constructing a model to study the glycemic response to different foods in normal and diabetic subjects. In this study, serum glucose and insulin values from individual normal subjects (Diab. 26, 1178) following the ingestion of different foods (corn, rice, bread, potato) high in complex carbohydrate were analyzed to determine glucose infusion rates (J) into the blood from the gut as a function of time following the ingestion of the food item. A Modular Modeling Program was designed to allow selection of data, curve fit, model, and tuning of parameters. The two models used were from Ackerman et al (Phys. Med. Biol. 9, 203) and the minimal model (VI) from Bergman and Cobelli (Fed. Proc. 39,110). The models were modified so that glucose and insulin values were used as input and J was the output. There was a good correspondence between the shape of the J curves predicted by the two models. While the J curves resembled serum glucose curves, they generally reached a peak earlier and declined more rapidly. Two peaks occurred in the J curves for bread, corn and rice. The second peaks may correspond to a delay in the release of glucose during digestion. The resulting infusion rate characterization of these foodstuffs maybe useful for modeling responses in diabetic patients with normal gut function but with impaired peripheral glucose utilization and in detecting abnormal gut function.

In many modeling situations, a set of values for the model parameters is regarded as characterizing an individual. The modeler may, however, be interested in estimating the distribution of parameter values in the population from which the individuals are sampled. Some applications of population estimation, a survey of approaches to the estimation problem and some current work will be discussed. The approaches discussed include the "naive pooled data approach," two stage methods, the first order method proposed by Sheiner and Beal and a nonparametric maximum likelihood procedure. General approaches employing Bayes' Theorem are also considered.