Progress in food & nutrition science最新文献

Since the establishment of a new social order in 1949, China's attempts to feed and nurture its large population has been a topic of serious study in many disciplines. This review focuses on dietary sources of Chinese population and incidence, increase and decline of important diet related health disorders in China during the last four decades. Literature published since 1949 on goiter, rickets, riboflavin deficiency, beri beri, vision impairment, favism, cancer, atherosclerosis and coronary heart disease, hypertension, dental and smoking related diseases, diabetes mellitus, pancreatitis, lactose intolerance, mineral deficiency, Kashin-Beck disease, parasitic diseases and genetic disorders are reviewed. Also presented selectively are reports related to ethnodietetics, health care, maternal health and pediatric care as well as longevity. In the 1980s, total caloric intake of Chinese population showed a 19% increase on a daily basis from that of late 1940s. In overall terms, plant derived foods supplied 93% of energy, 87% of protein and 55% of fat to the Chinese. Among the animal foods, pork remains the most common and least expensive form of meat, contributing more than 90% of China's total meat production excluding poultry and fish. In 1949, the life expectancy in China was only 36 years. In early 1980s, it has increased to 68 years. This increase in life expectancy is attributed mostly to improved nutrition and lowering of mortality due to decrease in infectious diseases. Though population, disease and mortality statistics of modern China are spotty and sometimes questionable, common consensus among the researchers is that since 1949 the public health situation in China has improved tremendously.

The results of efforts to identify the prevailing nutritional deficiency disorders in Bangladesh and major topics of local scientific investigation influencing those nutrient disorders are reviewed. Primary areas of emphasis include studies addressing nutritional status (especially vitamin A); factors influencing diarrheal incidence, morbidity and mortality; child nutrition; the influence of seasonal variations; and the implementation of successful intervention programs. Programmatic implications of the findings are presented.

Self-prescribed use of single micronutrients in excessive or pharmacologic dosage, without professional medical supervision, is on the increase. This raises potential problems of chronic toxicity and adverse interactions with prescribed and over-the-counter drugs. These questions are of special concern in the elderly, who utilize micronutrient supplements the most and at the same time have the greatest incidence of chronic illness and take the largest amount and variety of drugs. This review examines the toxicity and drug interactions of the thirteen vitamins and the trace elements chromium, selenium, and zinc.

A recent dietary survey shows that protein, energy and the majority of the mineral and vitamin intakes of the people in China are sufficient to meet their physiologic requirements. However, the dietary energy derived from cereals appear to be high and the dietary protein derived from animal foods is low. Thus, to improve the nutritional status of the Chinese people, a greater consumption of animal food is encouraged. The goal of an adequate adult diet is to maintain optimal health through a balanced intake of energy and all the essential nutrients. This can be achieved in China by the increase in food production through agriculture, fishery and animal husbandry, and by national planning utilizing the Recommended Dietary Allowances as the standard. Children are the future of our country. Hence, research on child nutrition should receive priority, particularly in the area of protein and energy requirements of pre-school children.

The principal lactogenic hormone, prolactin, secreted by the anterior pituitary is critical to the establishment of lactation, milk macronutrient content and milk production. The concentration of circulating prolactin increases during pregnancy so that by the end of gestation, levels are 10 to 20 times over normal amounts. However, prolactin is prevented from exerting its effect on milk secretion by elevated levels of progesterone. Following clearance of progesterone and estrogen at parturition, copious milk secretion begins. The minimal hormonal requirements for normal lactation to occur are prolactin, insulin and hydrocortisone. Prolactin stabilizes and promotes transcription of casein mRNA; may stimulate synthesis of alpha-lactalbumin, the regulatory protein of the lactose synthetase enzyme system; and increases lipoprotein lipase activity in the mammary gland. Prolactin levels decrease as lactation is established but nursing stimulates prolactin release from the pituitary which promotes continued milk production. Prolactin is secreted into milk at levels representative of the average circulating concentration. The physiological significance of milk prolactin to the infant is uncertain. Prolactin exists in three heterogenic forms which possess varying biological activity. The monomer with a molecular weight of 23 kDa is found in greatest quantity and is the principal biologically active form. The pattern of heterogeneity changes during pregnancy to favor even more monomer in proportion to the dimer. However, during lactation, the proportion of the monomer in circulation decreases in response to selective uptake of the monomer by the mammary gland. Over 90 percent of the prolactin in milk is present as the monomer. Prolactin may exert some of its biological effect by a shift in the ratio of active to less active forms of the molecule.

The most accurate measurement of energy expenditure (EE) in free-living individual subjects is by the doubly-labelled water technique. The minute-by-minute heart rate (fH) method, while not yet suitable for individuals, will give excellent measurements of EE in small groups of subjects as well as the pattern of EE while wearing the fH recorder. In adults, the few studies available indicate that chronic energy deficiency (CED) results in decreased energy expenditure. In pre-school children, CED results in decreased activity as a first line of defense against decreased rate of growth. In marginally malnourished school children, the lower levels of EE are the results of their smaller size. However, they are unable to cope with situations of increased activity above ordinary levels. The relative effort exerted by control and undernourished boys and girls 6-16 y of age averaged approximately 25% VO2 max during 12 h of school days. There was a -3% change with age but there were no sex or nutritional status effects on average % VO2 max. It is suggested that this relative constancy in % VO2max in such disparate groups may be indicative of some physiological regulation of activity levels.

The metallothioneins are small, cysteine-rich proteins that have the capacity for high affinity binding of heavy metal ions, and whose synthesis is regulated by metal ion concentrations. These properties suggest that they play pivotal roles in the metabolism of the relatively nontoxic essential metals (zinc and copper), as well as toxic heavy metals (cadmium), a concept supported by a variety of studies of cells in culture, as well as in intact animals. Expression of the metallothionein genes may have important implications in the nutritional status of the animal, in its response to stresses (inflammation, heavy metal toxicity), and in embryonic, fetal and neonatal development. The complementary DNAs and genes that encode the metallothioneins have been cloned and analyzed from a wide variety of eukaryotes. Striking features of the metallothioneins include: their high degree of amino acid sequence similarity (including conservation in the placement of cysteine residues in the molecule reflecting their function in metal binding); a conserved tripartite gene structure; and their transcriptional induction by metal ions, as well as other hormonal and environmental stimuli. The precise mechanisms and biochemical pathways by which cells transduce environmental signals into transcriptional induction of the metallothionein genes are beginning to be defined. Recent studies indicate that metal effects are exerted via positive trans-acting factors induced to interact with cis-acting DNA sequences in the promoter, in turn leading to transcriptional induction. However, the metallothionein gene promoter is structurally complex, and contains binding sites for a variety of nuclear proteins that likely regulate basal as well as induced levels of expression of these genes. Recent studies also suggest the possible involvement of post-transcriptional processes in the regulation of metallothionein levels in the cell. Furthermore, evidence of striking differences in the levels of metallothionein gene expression among various cell types in vivo have recently been documented. Although several detailed reviews of the metallothioneins have been published recently, this review will focus, in large part, on the molecular biology of the metallothioneins, with particular emphasis on recent advances in our understanding of the mechanisms regulating expression of these interesting and important genes. Given the large volume of literature on the metallothioneins and the space limitations of this review, it is impossible to comprehensively cite the studies of each of my colleagues who have contributed so much to this field. Instead the reader is often directed to reviews of this subject for much of the earlier literature, and emphasis is placed on more current publications in this field.

Investigations of recent outbreaks and sporadic cases of listeriosis in North America and other countries have shown that the infection can be foodborne. Pregnant women and their fetuses, the elderly, and immuno-compromised individuals are at increased risk of listeriosis. Listeria monocytogenes, the causative bacterium, is widespread in nature and is found in many foods. It can grow at refrigerator temperatures and is resistant to adverse conditions and to several antibiotics. The generally low levels of the organism found in foods require procedures to optimize their detection and recovery. Occurrence and characteristics of the bacterium, virulence and disease symptoms, transmission to humans, incidence and behavior in foods, and means of controlling growth in foods are reviewed.

Studies using specific and sensitive techniques, to assess the functional status of thyroid in areas with iodine deficiency and endemic goitre, show large scale prevalence of functional failure among neonates, children and adults. As thyroxine deficiency can impair quality of human resource, poverty and socio-economic backwardness in endemic areas may have a causal nexus with nutritional iodine deficiency. Eradication of NID, therefore, is an essential first step in the socio-economic transformation, through human resource development, of goitre endemias in developing countries.