Progress in food & nutrition science最新文献

Marine oils are receiving increasing attention as a source of C 20 and C 22 carbon omega-3 polyenoic fatty acids. The provision of preformed EPA and DHA from marine oils has profound implications for health and disease. Their role as precursors for the synthesis of eicosanoids and docosanoids explains many of the multisystemic effects observed when they are administered. Furthermore under some physiologic conditions such as preterm birth the evidence suggests that C 18 omega-3 fatty acids are not sufficiently converted to DHA to allow for biochemical and functional normalcy, thus DHA may be considered a conditionally essential nutrient for normal eye and brain development. Under disease conditions EPA plays a major role in modifying the balance between omega-6 and omega-3 derived eicosanoids thus modulating related functions. The use of marine oils has some potential risks that can be circumvented by careful processing, storing and preserving the unsaturated fatty acids. Technological procedures based on chemical and physical separation of the unsaturated fatty acids has permitted the elaboration of concentrated EPA and DHA for clinical testing. The development of structured lipids has allowed the synthesis of novel forms of EPA and DHA delivery. Further uses of marine oil to optimize health and prevent disease are predicted based on recent knowledge and technological developments.

This paper highlights various issues in relation to the workload of women in developing countries and its impact on health and nutritional status. The determining factors in women's workload and work-time and the methods employed for assessment are described. The drawbacks of the methods used and the resulting inconsistencies in the data are reviewed. How women are subjected to different health stresses owing to their productive and reproductive roles has been examined under three categories of work: economic, domestic and agricultural. The interaction of women's workload and health is complex and multifactorial owing to variations in the environment and socio-economic conditions within developing countries. There is a critical need to re-examine the assumptions existing about women's workload in programmes aimed at reducing work-time and workload of women in developing countries.

The intestinal microflora represents an enormous cell mass and has a high metabolic capacity. The symbiotic efficacy of these microbes in humans is still a matter of discussion. Of particular interest, from a biogenetic point of view, are potential symbiotic relations between the bifidobacterial microflora and the breast-fed infant. Our group has conducted studies related to this topic; they were aimed at determining the dimension of microbial assimilation by the host. Our studies with 15N-labeled bifidobacteria have shown that the bifidobacterial microflora is capable of upgrading nonessential nitrogen such as urea nitrogen for the synthesis of microbial protein. Oral single pulse labelings with 15N-labeled bifidobacteria were absorbed to approximately 90% and retained in the infant's protein pool to approximately 70%. These findings demonstrate the high intensity of the substrate flow from the microflora to the host. This might become important under conditions of marginal food protein intake or during periods of accelerated growth.

Fatty acids are molecules that differ in the length of their carbon chain and the number of double bonds within them. Each of the resulting "families" has its own peculiarities as regards energy, structure and metabolism. Passing from the short, saturated chains to the very long polyunsaturated ones produces an increasing degree of specialization in metabolic and structural functions important for the body's development and general homeostasis. The fetus and neonate (especially if preterm), the breast-fed and weaning baby all need fatty acids in the right amounts and ratios to achieve full expression of their genetic growth potential, especially of nerve tissues. Intake in these age groups depends on dietary factors such as the mother's diet during pregnancy, the type of milk (human or artificial), and the weaning schedule. Later in childhood and in adolescence not only must the body's somatic growth needs be covered, but intake must be adequate to lay the basis for prevention of chronic-degenerative pathologies. Dietary recommendations are therefore based on encouraging a normocaloric feeding pattern, with a controlled total and saturated lipid proportion and balanced intake of unsaturated fatty acids.

Nephrocalcinosis is a common disorder in female rats. Various etiological factors are involved in the pathogenesis, e.g. sex, age, genetical and dietary factors. Dietary phosphorus concentration appears to be of crucial importance in the induction of nephrocalcinosis. The pathological changes in calcinotic kidney tissue are described. Possible mechanisms underlying nephrocalcinogenesis are discussed. Phosphorus concentration within the proximal tubule may be the major determinant of nephrocalcinogenesis.

This review summarises the methods available for the analysis of phytate and structurally related molecules, i.e., inositol polyphosphates. Phytate has been determined by colorimetry, low pressure ion exchange column chromatography, phosphorus-31 fourier transform nuclear magnetic resonance spectroscopy (31P FT NMR), near-infrared reflectance spectroscopy and high performance liquid chromatography (HPLC). Among these techniques anion exchange column chromatography and HPLC were shown to be best suited for separation of inositol phosphates. Since inositol phosphates do not have a characteristic absorption spectrum, their detection in HPLC analysis is limited to methods employing monitoring of refractive index, post column reaction products, conductivity or indirect detection although other detection methods may be feasible. As refractive index detection under isocratic eluent conditions is relatively easy to manipulate, anion-exchange HPLC methods using a low capacity column or ion-pair HPLC methods are recommended for the analysis of inositol phosphates in nutritional studies.

Weight gain during pregnancy is considered a major determinant of fetal growth. Low maternal weight gain is associated with an increased incidence of low birth weight infants who are at higher risk for increased mortality. For the past twenty years, weight gain recommendations have been centered around one value (11 kg) as representative of a weight gain objective. Newer recommendations are based on what is considered optimal infant outcomes and not necessarily on maternal health considerations. These recent recommendations indicate the importance of pregravid weight in setting weight gain goals with overweight gravida advised to gain less than normal weight or underweight gravida. When confounding variables are controlled, maternal weight gain is similar in adolescents and older women. Reports on weight loss during the postpartum period indicate a high degree of variability in total weight change. In general, with current levels of weight gain, each successive birth adds about 1 kg of body weight above that normally gained with age. There is very little evidence to suggest that breast feeding as compared to other methods of infant feeding, causes body weight to return to prepregnancy levels at a faster rate.

The literature is briefly summarized as to immunologic modifications caused by the human acquired immune deficiency syndrome (AIDS), immunocompetence at various nutritional states of vitamin E, and the immunoenhancing properties of vitamin E. The abnormalities of immune components present in AIDS are similar to those that are stimulated or restored by intake of high doses of vitamin E. Dietary supplementation of vitamin E with an adequate nutrition support or concomitant use of this vitamin with current drug therapies [For example, Zidovudine (AZT)] may increase the therapeutic efficiency of drugs and enhance immune resistance to opportunistic infections associated with AIDS. Supplementation with vitamin E may also decrease the progression of the disease to AIDS. Unlike many pharmacological agents which are toxic at low levels, vitamin E is non-toxic over a wide range of intakes. A moderately high dose may be used to target and stimulate some specific immune cells destroyed by HIV infection. However, further interdisciplinary studies are much needed to relate various levels of intake of this vitamin as a supplement to clinical outcomes during HIV infection and establish the role for this vitamin in human immunity during AIDS.

Although the effects of cigarette smoking on a variety of diseases, from cancer through emphysema and cardiovascular illness are well documented, direct effects on the levels of macro- and micronutrients in the body are reported less frequently. In fact, imbalances in these nutrients may have a role in many of the pathological conditions attributed to smoking. Tobacco smoke contains numerous compounds emitted as gases and condensed tar particles, many of them being oxidants and prooxidants, capable of producing free radicals thus enhancing lipid peroxidation in biological membranes. Vitamin E, vitamin C, B-carotene and selenium are involved in the overall cellular anti-oxidant defense against deleterious effects of reactive oxygen species. Smoking has been shown to lower the level of vitamin C and B-carotene in plasma. Cadmium, naturally found in tobacco, decreases the bioavailability of selenium and acts antagonistically to zinc, a cofactor for the antioxidant enzyme, superoxide dismutase. Vitamin E, the principle lipid-soluble antioxidant, may be at suboptimal levels in tissues of smokers. In addition, tobacco constituents have been shown to reduce levels of several vitamins of the B-complex. Nutritional status in smokers may be further compromised by an inadequate diet. Data from the Second National Health and Nutrition Examination Survey indicates that smokers are less likely to consume fruits and vegetables, particularly those high in vitamin C and carotenes. Cessation of smoking is the obvious solution to ending cigarette-related problems. In the world as it is, however, the medical community should be responsible for making recommendations to lower the risk in smokers to tobacco related diseases. Nutritionists could have a role in this process. There exists a lively debate as to where levels of nutrients should be set. Additional vitamin C has already been recommended for smokers. Should other antioxidants also be increased? Arguments for the against are considered.

Biochemical evidence collected from both clinical and non-institutionalized populations indicate that iron and folate deficiencies frequently occur simultaneously. Supplementation trials of iron-deficient patients with either iron or iron and folate has helped to illustrate that a complex interrelationship exists between these two nutrients. Controlled animal trials in which dietary iron and folate content has been systematically manipulated reveal that iron deficiency can cause altered folate utilization. The impact of iron deficiency on folate metabolism is most dramatic during the reproductive and neonatal stages of the life cycle. Rat pups and piglets nursed by dams fed iron-depleted diets exhibit signs of altered folate utilization. Depressed milk folate secretion is an early manifestation of iron deficiency in the rat dam and is a prime factor responsible for folate depletion in their nursing pups. Impaired milk folate secretion during iron deficiency is not due to a decrease in the amount of folate supplied to the mammary gland; rather, the defect causing this reduction is specific to the mammary gland.