Progress in food & nutrition science最新文献

Endemic skeletal fluorosis is a chronic metabolic bone and joint disease caused by ingesting large amounts of fluoride either through water or rarely from foods of endemic areas. Fluoride is a cumulative toxin which can alter accretion and resorption of bone tissue. It also affects the homeostasis of bone mineral metabolism. The total quantity of ingested fluoride is the single most important factor which determines the clinical course of the disease which is characterized by immobilization of joints of the axial skeleton and of the major joints of the extremities. A combination of osteosclerosis, osteomalacia and osteoporosis of varying degrees as well as exostosis formation characterizes the bone lesions. In a proportion of cases secondary hyperparathyroidism is observed with associated characteristic bone changes. Contrary to earlier thinking, severe crippling forms of skeletal fluorosis are seen in paediatric age group too. Increased metabolic turnover of the bone, impaired bone collagen synthesis and increased avidity for calcium are features in fluoride toxicity. Osteosclerotic picture is evident when small doses of fluoride are ingested over a long period of time during which calcium intakes are apparently normal while osteoporotic forms are common in paediatric age group and with higher body load of the element. Alterations in hormones concerned with bone mineral metabolism are seen in fluorosis. Kidney is the primary organ of excretion for fluorides. Age, sex, calcium intake in the diet, dose and duration of fluoride intake and renal efficiency in fluoride handling are the factors which influence the outcome. Serum parameters rarely help in the diagnosis. Elevated urinary fluoride and increased bone fluoride content are indicators of fluoride toxicity. Fluorosis is a preventable crippling disease. No effective therapeutic agent is available which can cure fluorosis. Industrial fluorosis is on the increase on a global basis. Bone density measurement is a tool for early diagnosis.

High intakes of the macronutrients--proteins, lipids, and carbohydrates in the form of excess energy-have some cancer stimulating properties. On the contrary, epidemiologic and animal laboratory data indicate that high-level supplementation of some micronutrients--certain vitamins, minerals, and lipotropes, as well as some non-nutrients, most notably various types of dietary fiber, may be useful in the prevention of cancer. A wealth of data exists for macronutrients whereas most micronutrients are almost unstudied concerning their role in cancer prevention. Vitamins A, E, and C and selenium are the most well-studied micronutrients, and are recognized as effective with significant anticancer effects, at least in animal models. There are minimal data to suggest that some other micronutrients may also exert varying degrees of incidence reduction on one or more types of cancer. This is most true for folic acid, manganese, molybdenum, copper, the amino acids phenylalanine and methionine, and the lipotrope choline. Zinc and vitamins B1, B2, B6, B12 and pantothenic acid have even less data, and some data are contradictory. Therefore, it is premature to make recommendations concerning their usefulness in cancer prevention at present.

The immune system plays a key role in the body's ability to fight infection and reduce the risk of developing tumors, autoimmune and degenerative disease. Nutritional deficiencies and excesses influence various components of the immune system. Early studies investigating the association between nutrition and immunity focused on generalized protein-energy malnutrition, particularly in children in developing countries. The extent of immunological impairment depends not only on the severity of malnutrition but on the presence of infection and on the age of onset of nutritional deprivation, among other factors. In industrialized nations, immune function has been shown to be compromised in many malnourished hospitalized patients, small-for-gestational age infants, and the elderly. Obesity also may adversely influence immune function. Imbalances of single nutrients are relatively uncommon in humans, and investigations of protein and amino acids and specific vitamins, minerals, and trace elements generally are carried out in experimental animals. Deficiencies of protein and some amino acids, as well as vitamins A, E, B6 and folate, are associated with reduced immunocompetence. In contrast, excessive intake of fat, in particular polyunsaturated fatty acids (e.g. linoleic and arachidonic acids), iron, and vitamin E are immunosuppressive. Trace elements modulate immune responses through their critical role in enzyme activity. Both deficiency and excess of trace elements have been recognized. Although dietary requirements of most of these elements are met by a balanced diet, there are certain population groups and specific disease states which are likely to be associated with deficiency of one or more of these essential elements. The role of trace elements in maintenance of immune function and their causal role in secondary immunodeficiency is increasingly being recognized. There is growing research concerning the role of zinc, copper, selenium, and other elements in immunity and the mechanisms that underlie such roles. The problem of interaction of trace elements and immunity is a complex one because of the frequently associated other nutritional deficiencies, the presence of clinical or subclinical infections which in themselves have a significant effect on immunity, and finally the altered metabolism due to the underlying disease. There are many practical applications of our recently acquired knowledge regarding nutritional regulation of immunity.(ABSTRACT TRUNCATED AT 400 WORDS)

The response to surgical injury is mediated through the hypothalamus and is characterised by the release of catecholamines, glucocorticoids, growth hormone and glucagon; the suppression of insulin secretion and changes in other endocrine systems. These hormonal responses trigger a cascade of metabolic adjustments leading to catabolism and substrate mobilization in the postoperative period. There is evidence that a severe and prolonged catabolic reaction to injury may be associated with an increased morbidity and mortality in high-risk adult patients. This article reviews the historical background of investigation in this field, together with recent advances in the understanding of the complex metabolic phenomena following surgery. These changes are discussed with particular reference to therapeutic manipulation of the stress response using anaesthetic, hormonal or nutrition regimens. It is concluded that further research in this field may provide major clinical benefits in the management of critically ill patients undergoing surgical stress.

Rats and chicks obtain little or no bioefficacy from the D-isomers of lysine, threonine, arginine, histidine and cystine. D-isomers of the branched-chain amino acids, i.e., leucine, isoleucine and valine (LEU, ILE, VAL) are utilized relatively well by chicks but poorly by rats. D-tryptophan is utilized efficiently by rats and pigs, but inefficiently by chicks, poults, mice and humans. The D-forms of phenylalanine (PHE), tyrosine and methionine (MET) are utilized well by both rats and chicks. Keto and hydroxy analogs of LEU, ILE, VAL, PHE and MET are utilized by both rats and chicks. The L-isomer of the alpha-hydroxy analogs of ILE and PHE has bioactivity while the D-isomer has no bioactivity. D-OH-LEU and D-OH-VAL have bioactivity, but they are less efficacious than their corresponding L-OH analogs. D-OH-MET is a more efficient precursor of L-MET than is L-OH-MET. In general, alpha-keto analogs of LEU, ILE, VAL, PHE and MET are utilized no more efficiently than the active isomeric form of the alpha-OH analogs of these amino acids. The alpha-OH and alpha-keto analogs of ILE are utilized relatively efficiently when used to replace only a portion of L-ILE in a purified amino acid diet for either rats or chicks; utilization of L-ILE analogs is poor, however, when all of the dietary L-ILE is replaced by analog material. In addition to MET and cyst(e)ine, many other dietary sulfur compounds must be considered when dealing with sulfur amino acid bioactivity. Glutathione, taurine, N-acetyl-MET, lanthionine and inorganic sulfate all have sulfur amino acid bioactivity under certain circumstances. Likewise, both oral and endogenous carnosine have histidine bioactivity, and purines, pyrimidines and urea have dispensable amino acid biosynthetic activity.

Health professionals concerned with improving the nutritional status of populations are facing numerous problems ranging from emaciation to overnutrition. This review article addresses the complexity, the relative significance and the interaction of factors leading to the nutritional profile of specific groups and individuals. When availability of food is threatened, the programs designed to reduce the incidence of malnutrition must balance the food supply with energy resources and population needs as well as encourage economic improvement of food distribution systems. For those persons having access to an abundant food supply, social forces and technological factors may affect food patterns, resulting in unbalanced diets associated with chronic diseases. Misinterpretation of reliable scientific findings is a major cause of abnormal nutrition behaviour. Overreaction to health messages may precipitate such conditions as anorexia nervosa or nutrient toxicity. Adverse food reactions, real or imagined, lead to restrictions in food selection. Excessive austerity in food use negates the pleasure of eating, a useful mechanism in food choice ensuring food diversity.

The maternal nutritional status is considered as one of the most important factors influencing the pregnancy and the state of the offspring. There are limited data available on inadequate intake, especially before conception. A variety of nutritional and non-nutritional factors can act during the preconceptional period. Prepregnancy body weight and gestational weight gain have an independent but cumulative influence on the birth weight. The vitamin deficiency in preconceptional period, especially of folates, seems to be associated with neural tube defects. The infants of women with total gestational weight gain below 9 kg have the mean birth weight always lower than those of women with weight gain more than 9 kg in all three categories of preconceptional relative weight (i.e. less than 95%, from 95% to 105% and greater than 105%). Also the proportion of infants with birth-weight greater than 2500 g is higher in average (6.2%) and under-weight (4.4%) groups than in those over-weight (1.8%). Several other maternal nutritional as well as non nutritional variables are related with the pregnancy outcome. Among those with harmful effect on pregnancy outcome since preconceptional period, are alcohol drinking and smoking. Work outside the home can be associated with preterm deliveries and low-birth-weight infants, but the results are not consistent. Nutritional intervention, energy and/or protein supplementation also contribute to an increase of the birth-weight. As far as the antenatal care is concerned, only few studies investigated, with a scientific rigour the relation if any between prenatal care and pregnancy outcome. We concluded that the available evidence confirms a significant impact of preconceptional nutrition on pregnancy outcome. A sensitive evaluation of nutritional status in preconceptional period seems to be a positive strategy for prevention of at risk pregnancies. There is a clear need of prospective human studies with aim to relate the nutrient status of future mother to the evolution of her pregnancy.

Dietary alteration or intervention is an ideal method of preventing or treating hypertension. Medication may be eliminated or reduced in many cases. Correction of obesity and alcohol abuse are confirmed methods of treating hypertension. Reduction of sodium intake is effective in that portion of the population which is salt-sensitive. Probably, the ratio of sodium to potassium is of importance and increasing potassium intake while reducing sodium intake is effective in many situations. Evidence is being reported which indicates that adequate intake of calcium, and perhaps magnesium, is effective in preventing hypertension. Limited information indicates that a sufficiency of dietary essential fatty acids and fibre are effective in hypertension prevention. The role of dietary protein, carbohydrates, fat, cholesterol, vitamins, and essential elements (other than those mentioned above) in the pathogenesis has not been fully elucidated at this time, but there are indications that adequate intakes are beneficial in hypertension. Water hardness may have some effect in reducing hypertension incidence, and any effectiveness would probably result from calcium and magnesium in the drinking water. Animal studies and limited human studies indicate some detrimental effects of heavy metals, such as lead and cadmium, upon the pathogenesis of hypertension. Information regarding caffeine intake is inconclusive.

Evidence pertaining to the role of dietary factors in carcinogenesis comes from both epidemiological studies and laboratory experiments. In 1982, the Committee on Diet, Nutrition, and Cancer of the National Research Council conducted a comprehensive evaluation of this evidence. That assessment as well as recent epidemiological and laboratory investigations suggest that a high fat diet is associated with increased susceptibility to cancer of different sites, particularly the breast and colon, and to a lesser extent, the prostate. Current data permit no definitive conclusions about other dietary macroconstituents including cholesterol, total caloric intake, protein, carbohydrates and total dietary fiber. Specific components of fiber, however, may have a protective effect against colon cancer. In epidemiological studies, frequent consumption of certain fruits and vegetables, especially citrus fruits and carotene-rich and cruciferous vegetables, is associated with a lower incidence of cancers at various sites. The specific components responsible for these effects are not clearly identified, although the epidemiological evidence appears to be most consistent for a protective effect of carotene on lung cancer and less so for vitamins A and C and various cancer sites. The laboratory evidence is most consistent for vitamin A deficiency and enhanced tumorigenesis, and for the ability of various nonnutritive components in cruciferous vegetables to block in-vivo carcinogenesis. The data for minerals and carcinogenesis are extremely limited, although preliminary evidence from both epidemiological and laboratory studies suggests that selenium may protect against overall cancer risk. Frequent consumption of cured, pickled, or smoked foods, possibly because they may contain nitrosamines or polycyclic aromatic hydrocarbons, appears to increase the risk of esophageal or stomach cancer, however, the specific causative agents in these foods are not clearly identified. Excessive alcohol consumption among smokers appears to be associated with an elevated risk of cancers of the oral cavity, esophagus, larynx, and respiratory tract. The mechanisms of action of dietary factors on carcinogenesis are poorly understood. The NRC committee, and more recently, the National Cancer Institute and the American Cancer Society have proposed interim dietary guidelines to lower the risk of cancer. These guidelines are consistent with general dietary recommendations proposed by U.S. government agencies for maintenance of good health.(ABSTRACT TRUNCATED AT 400 WORDS)