首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 343 毫秒
1.
BACKGROUND: Ascorbic acid has a pronounced enhancing effect on the absorption of dietary nonheme iron when assessed by feeding single meals to fasting subjects. This contrasts with the negligible effect on iron balance of long-term supplementation with vitamin C. OBJECTIVE: Our goal was to examine the effect of vitamin C on nonheme-iron absorption from a complete diet rather than from single meals. DESIGN: Iron absorption from a complete diet was measured during 3 separate dietary periods in 12 subjects by having the subjects ingest a labeled wheat roll with every meal for 5 d. The diet was freely chosen for the first dietary period and was then altered to maximally decrease or increase the dietary intake of vitamin C during the second and third periods. RESULTS: There was no significant difference in mean iron absorption among the 3 dietary periods despite a range of mean daily intakes of dietary vitamin C of 51-247 mg/d. When absorption values were adjusted for differences in iron status and the 3 absorption periods were pooled, multiple regression analysis indicated that iron absorption correlated negatively with dietary phosphate (P = 0.0005) and positively with ascorbic acid (P = 0.0069) and animal tissue (P = 0.0285). CONCLUSIONS: The facilitating effect of vitamin C on iron absorption from a complete diet is far less pronounced than that from single meals. These findings may explain why several prior studies did not show a significant effect on iron status of prolonged supplementation with vitamin C.  相似文献   

2.
Interactions among dietary manganese, heme iron, and nonheme iron in women.   总被引:1,自引:0,他引:1  
The relationship among dietary intake of heme iron, nonheme iron, and manganese on indexes of hematological and nutritional status in regard to manganese of 47 women consuming their typical diets was investigated. Increasing dietary iron intake, by consuming more nonheme iron in the diet, had questionable effects on hematological status (hematocrit values and ferritin and transferrin concentrations) and negative effects on nutritional status in regard to manganese (serum manganese, urine manganese, and lymphocyte manganese-dependent superoxide dismutase activity). In contrast, heme-iron intake was positively correlated with hematological status and had no consistent effect on nutritional status in regard to manganese. Differences in dietary manganese intake had no consistent effect on indices of manganese or iron status, possibly because foods that contain significant amounts of manganese (green vegetables, breads, and cereals) often contain significant amounts of nonheme iron. Thus, increasing dietary manganese intake by consuming these foods is apt to have limited impact on manganese status because of the interaction between nonheme iron and manganese.  相似文献   

3.
Iron deficiency is a concern in both developing and developed (industrialized) countries; and young women are particularly vulnerable. This review investigates dietary determinants of and possible solutions to iron deficiency in young women living in industrialized countries. Dietary factors including ascorbic acid and an elusive factor in animal protein foods (meat; fish and poultry) enhance iron absorption; while phytic acid; soy protein; calcium and polyphenols inhibit iron absorption. However; the effects of these dietary factors on iron absorption do not necessarily translate into an association with iron status and iron stores (serum ferritin concentration). In cross-sectional studies; only meat intake has consistently (positively) been associated with higher serum ferritin concentrations. The enhancing effects of ascorbic acid and meat on iron absorption may be negated by the simultaneous consumption of foods and nutrients which are inhibitory. Recent cross-sectional studies have considered the combination and timing of foods consumed; with mixed results. Dietary interventions using a range of focused dietary measures to improve iron status appear to be more effective than dietary approaches that focus on single nutrients or foods. Further research is needed to determine optimal dietary recommendations for both the prevention and treatment of iron deficiency.  相似文献   

4.
Hypoferremia is more prevalent in obese than nonobese adults, but the reason for this phenomenon is unknown. To elucidate the role dietary factors play in obesity-related hypoferremia, the intake of heme and nonheme iron and the intake of other dietary factors known to affect iron absorption were compared cross-sectionally from April 2002 to December 2003 in a convenience sample of 207 obese and 177 nonobese adults. Subjects completed 7-day food records, underwent phlebotomy for serum iron measurement, and had body composition assessed by dual-energy x-ray absorptiometry, during a 21-month period. Data were analyzed by analysis of covariance and multiple linear regression. Serum iron (mean+/-standard deviation) was significantly lower in obese than nonobese individuals (72.0+/-61.7 vs 85.3+/-58.1 microg/dL [12.888+/-11.0443 vs 15.2687+/-10.3999 micromol/L]; P<0.001). The obese cohort reported consuming more animal protein (63.6+/-34.5 vs 55.7+/-32.5 g/day; P<0.001) and more heme iron (3.6+/-2.8 vs 2.7+/-2.6 mg/day; P<0.001). Groups did not differ, however, in total daily iron consumption, including supplements. Obese subjects reported consuming less vitamin C (77.2+/-94.9 vs 91.8+/-89.5 mg/day; P=0.01), which may increase absorption of nonheme iron, and less calcium (766.2+/-665.0 vs 849.0+/-627.2 mg/day; P=0.038), which may decrease nonheme iron absorption, than nonobese subjects. Groups did not significantly differ in intake of other dietary factors that can impact absorption of iron, including phytic acid, oxalic acid, eggs, coffee, tea, zinc, vegetable protein, or copper. After accounting for demographic covariates and dietary factors expected to affect iron absorption, fat mass (P=0.007) remained a statistically significant negative predictor of serum iron. This cross-sectional, exploratory study suggests that obesity-related hypoferremia is not associated with differences in reported intake of heme and nonheme iron or intake of dietary factors that can affect iron absorption.  相似文献   

5.
Human subjects absorb heme iron (Fe) more efficiently than nonheme Fe under most conditions. Meat enhances nonheme Fe absorption from most diets. It is not known whether these effects also occur in the pig, a promising model for human Fe absorption studies. The objective of this study was to compare Fe bioavailability from diets containing nonheme Fe (NHI), nonheme Fe with meat (NHI/M) and heme Fe (HI) in the weanling pig. Iron bioavailability was measured by hemoglobin (Hb) repletion assay. Diets were formulated to contain 150 mg Fe/kg diet. Nonheme Fe was supplied as ferric citrate and heme Fe as dried animal red blood cells. Pigs were made anemic by reducing the standard Fe injection at birth to 30 mg and feeding a low Fe transition diet post-weaning until age 41 days. At 41 days of age, pigs were assigned to 3 groups of 8 animals such that mean Hb concentration and body weight of each group were nearly equal. Groups were randomly assigned to 1 of 3 repletion diets. After 7 days feeding, Hb repletion efficiency (HRE) was 21.8% in pigs fed the NHI/M diet compared to 11.2% and 9.1% in pigs fed the NHI or HI diets, respectively. The results presented here demonstrate that, in Fe-deficient weanling pigs, meat increases nonheme Fe bioavailability from corn-based diets while heme Fe, supplied by dried animal red blood cells, is no more bioavailable than Fe from ferric citrate. The results of this study provide further evidence of the validity of the pig model for studying food Fe bioavailability.  相似文献   

6.
Heme iron absorption during pregnancy and the role of hepcidin in regulating dietary heme iron absorption remains largely unexplored. The objective of this research was to examine relative differences in heme (animal based) and nonheme (ferrous sulfate) iron utilization. This study was undertaken in 18 pregnant (ages 16-32 y; wk 32-35 of gestation) and 11 nonpregnant women (ages 18-27 y). Women were randomly assigned to receive both an animal-based heme meal (intrinsically labeled (58)Fe pork) and labeled ferrous sulfate ((57)Fe) fed on alternate days. Blood samples obtained 2 wk postdosing were used to assess iron status indicators and serum hepcidin and iron utilization based on RBC incorporation of iron isotopes. Heme iron utilization was significantly greater than nonheme iron utilization in the pregnant (47.7 ± 14.4 vs. 40.4 ± 13.2%) and nonpregnant women (50.1 ± 14.8 vs. 15.3 ± 9.7%). Among pregnant women, utilization of nonheme iron was associated with iron status, as assessed by the serum transferrin receptor concentration (P = 0.003; r(2) = 0.43). In contrast, heme iron utilization was not influenced by maternal iron status. In the group as a whole, women with undetectable serum hepcidin had greater nonheme iron utilization compared with women with detectable serum hepcidin (P = 0.02; n = 29); however, there were no significant differences in heme iron utilization. Our study suggests that iron utilization from an animal-based food provides a highly bioavailable source of dietary iron for pregnant and nonpregnant women that is not as sensitive to hepcidin concentrations or iron stores compared with ferrous sulfate.  相似文献   

7.
《Nutrition reviews》1997,55(6):233-239
Iron deficiency can be caused not only by diets deficient in iron but by poor absorption of available dietary iron. Extrinsically tagging foods with radioiron allows the exact measurement of iron absorbed from heme and nonheme iron foods. It has furthered the study of the effect of enhancers and inhibitors of iron absorption. As a result, we have a greater understanding of why iron deficiency and iron deficiency anemia are prevalent in populations of low socioeconomic status and of which food vehicles and irbn compounds are most suitable for iron fortification.  相似文献   

8.
《Nutrition Research》1986,6(6):619-626
Written dietary questionnaires were kept for two nonconsecutive weekdays by 355 male and 382 female Utah school children, mean age 7.5 years, assisted by their parents and recorded by household measure. The intake of dietary ascorbic acid and total iron consumed was evenly distributed among the meals; approximately 10% of these nutrients was consumed at snacks. Approximately 36% of the meat, fish, poultry and the iron in those products was consumed at lunch while approximately 54% of the meat, fish, poultry and the iron contained in those products was consumed at dinner. Only 5% of the iron from meat, fish, poultry products was consumed as snacks. Intakes by percent of heme iron, nonheme iron, available heme iron, available nonheme iron and total available iron were calculated by meal. The available iron distribution for breakfast, lunch, dinner, and snacks was 21%, 30.8%, 42.5% and 5.7%, respectively. Such information can be used to increase available iron intake of individuals.  相似文献   

9.
Iron deficiency is widely observed worldwide, yet, paradoxically, iron is the most plentiful heavy metal in the earth's crust. Although absorption of iron from the gastrointestinal tract is strictly controlled, excretion is limited to iron lost from exfoliation of skin and gastrointestinal cells, customary and abnormal blood loss, and menses. Individuals highly vulnerable to iron deficiency have high iron needs, as during growth or pregnancy; high iron loss, as during marked hemorrhage or excessive and/or frequent menstrual losses; or diets with low iron content or bioavailability. Food iron is classified as heme or nonheme. Approximately half of the iron in meat, fish, and poultry is heme iron. Depending on an individual's iron stores, 15% to 35% of heme iron is absorbed. Food contains more nonheme iron and, thus, it makes the larger contribution to the body's iron pool despite its lower absorption rate of 2% to 20%. Absorption of nonheme iron is markedly influenced by the levels of iron stores and by concomitantly consumed dietary components. Enhancing factors, such as ascorbic acid and meat/fish/poultry, may increase nonheme iron bioavailability fourfold.  相似文献   

10.
Adaptation in iron metabolism   总被引:1,自引:0,他引:1  
Humans can adapt successfully to a wide range of iron requirements and intakes. The lower limit of the adapted state is best defined by serum ferritin greater than or equal to 12 micrograms/L, because lower values indicate that iron stores are fully depleted. Successful adaptation is achieved by modifying the rate of gastrointestinal absorption according to body iron needs. Several dietary variables, including total intake, content of heme, and bioavailability of nonheme iron, determine the ceiling of the adaptive response when iron demands are high. With lesser demands the nature of the diet has a limited influence on body iron reserves, although there is some evidence that the adaptive response to variations in heme iron intake is less complete than the response to differences in nonheme bioavailability. How the intestinal mucosal cell achieves adaptation is one of the most important unsolved questions in iron metabolism.  相似文献   

11.
BACKGROUND: Few studies have examined the relation of iron status to diet in populations from developing countries with high levels of iron deficiency and diets of poor quality. OBJECTIVE: The objective was to identify nutrients, dietary constituents, and foods that are associated with better iron status in a rural Mexican population. DESIGN: A prospective cohort study was conducted in rural central Mexico. The subjects were 125 nonpregnant women aged 16-44 y. During the 12 mo before blood collection, food intakes were assessed repeatedly by a combination of dietary recalls, food weighing, and food diaries [mean (+/-SD) days of food intake data: 18.8 +/- 5.9 d]. Hemoglobin, hematocrit, and plasma ferritin were measured at the end of the study. RESULTS: Higher plasma ferritin concentrations were associated with greater intakes of nonheme iron and ascorbic acid after control for age, BMI, breast-feeding, season, and the time since the birth of the last child. Higher ascorbic acid intakes, but not higher intakes of heme and nonheme iron, predicted a lower risk of low hemoglobin and hematocrit values after control for the background variables. Consumption of the alcoholic beverage pulque predicted a lower risk of low ferritin and low hemoglobin values. Seasonal variation in ferritin, hemoglobin, and hematocrit values was observed. CONCLUSION: Better iron status was associated with greater intakes of foods containing nonheme iron and ascorbic acid. PULQUE:a beverage containing iron, ascorbic acid, and alcohol-may influence the iron status of women in rural central Mexico.  相似文献   

12.
Calcium is the only known component in the diet that may affect absorption of both nonheme and heme iron. However, the evidence for a calcium effect on iron absorption mainly comes from studies that did not isolate the effect of calcium from that of other dietary components, because it was detected in single-meal studies. Our objective was to establish potential effects of calcium on absorption of nonheme and heme iron and the dose response for this effect in the absence of a meal. Fifty-four healthy, nonpregnant women were selected to participate in 4 iron absorption studies using iron radioactive tracers. We evaluated the effects of calcium doses between 200 and 1500 mg on absorption of 5 mg nonheme iron (as ferrous sulfate). We also evaluated the effects of calcium doses between 200 and 800 mg on absorption of 5 mg heme iron [as concentrated RBC (CRBC)]. Calcium was administered as calcium chloride in all studies and minerals were ingested on an empty stomach. Calcium doses ≥1000 mg diminished nonheme iron absorption by an average of 49.6%. A calcium dose of 800 mg diminished absorption of 5 mg heme iron by 37.7%. In conclusion, we demonstrated an isolated effect of calcium (as chloride) on absorption of 5 mg of iron provided as nonheme (as sulfate) and heme (as CRBC) iron. This effect was observed at doses higher than previously reported from single-meal studies, starting at ~800 mg of calcium.  相似文献   

13.
BACKGROUND: The relation between iron status and atherosclerosis has long been a topic of debate. OBJECTIVE: We examined associations of cardiovascular disease (CVD) mortality with dietary intakes of iron (a possible prooxidant), zinc (a possible antioxidant), and alcohol (a disruptor of iron homeostasis). DESIGN: Postmenopausal women (n = 34 492) aged 55-69 y at baseline, who completed a food-frequency questionnaire, were followed for CVD mortality over 15 y. RESULTS: Among women who consumed >/=10 g alcohol/d, after adjustment for CVD risk factors in a model that contained dietary heme iron, nonheme iron, and zinc intakes, dietary heme iron showed a positive association, dietary nonheme iron showed a U-shaped association, and dietary zinc showed an inverse association with CVD mortality. For example, the relative risks (RRs) for categories of dietary heme iron were 1.0, 1.46, 1.52, 1.73, and 2.47 (P for trend = 0.04); corresponding RRs for dietary nonheme iron were 1.0, 0.93, 0.63, 0.83, and 1.20 (P for quadratic term = 0.02). The corresponding RRs for dietary zinc were 1.0, 0.61, 0.59, 0.57, and 0.37 (P for trend = 0.07). In an analysis restricted to those who consumed >/=30 g alcohol/d, the risk gradients strengthened. CONCLUSIONS: Our results suggest that a higher intake of heme iron might be harmful, whereas a higher intake of zinc might be beneficial in relation to CVD mortality in the presence of a trigger that can disturb iron homeostasis, such as alcohol consumption.  相似文献   

14.
BACKGROUND: Gene mutations associated with iron overload have been identified. How food and nutrient intakes affect iron status in persons who may be at risk of iron overload because their genetic status is unknown. OBJECTIVE: The objective was to determine the relation between food and nutrient intakes, HFE genotype, and iron status. Foods and nutrients associated with iron stores, with adjustment for gene mutations associated with hemochromatosis, were explored. DESIGN: A prospective cohort of women aged 35-69 y (the UK Women's Cohort Study) provided information on diet through a questionnaire and food diary; 6779 women in the cohort provided cheek cell samples, blood samples, or both, which were genotyped for C282Y and H63D mutations, and 2489 women also had their iron status assessed. Relations between serum ferritin and iron intake were investigated by using multiple linear regression, with adjustment for potential confounders. RESULTS: The strongest dietary association with serum ferritin concentration was a positive association with heme iron and not with nonheme or total iron. Weaker positive associations were seen with red and white meat, and negative associations were seen with total energy and white and brown whole-meal bread, independent of genotype and other potential confounders. The effect of genotype on ferritin concentrations primarily occurred after menopause, at which time a strong interaction between genotype and heme iron intake was observed. Other factors associated with serum ferritin concentrations were age, body mass index, blood donation, menopausal status, and HFE genotype. CONCLUSIONS: Postmenopausal women eating a diet rich in heme iron and who were C282Y homozygotes had the highest serum ferritin concentrations.  相似文献   

15.
The objective of this study was to estimate the amount of bioavailable iron (FeBIO) in the diet of Mexican children aged 12-59 mo through the application of algorithms that use dietary variables and analyze the association between estimated FeBIO and hemoglobin (Hb) concentration. Data were analyzed for 919 children aged 12-59 mo old who participated in a national probabilistic survey on nutrition, in which a 24-h dietary recall was applied and Hb concentration was determined through the use of portable photometers. Dietary intakes were determined for total iron, heme and nonheme iron, vitamin C, phytates, and meat (red meat, poultry, and fish). Using these dietary variables and distinct scenarios on body iron reserves, we used algorithms to estimate the amount of FeBIO in the diet. Linear regression models were adjusted to evaluate the association between FeBIO and Hb. The mean iron intake was 6.2 +/- 4.4 mg/d and the mean estimated FeBIO ranged between 0.14 and 0.37 mg/d depending on different assumptions about iron reserves, representing 2.7-6.1% of total iron intake. The Hb concentration, adjusted for altitude and presence of diarrhea, was positively associated with FeBIO in children 12-23 mo old (P < 0.05) but not in children 24-59 mo old. The estimated FeBIO is low in relation to physiological requirements and is compatible with existing high iron deficiency prevalence rates in Mexico. Although Hb is not a specific indicator of iron status, it was significantly associated with FeBIO.  相似文献   

16.
Iron deficiency is the most common and widespread nutritional disorder in the world. Consuming foods rich in dietary iron (high in both content and availability) is an effective way to alleviate iron deficiency. Iron from animal foods is more bio-available than iron from plant sources. This is due to the heme iron content in animal foods. According to the Monsen model, an average of 40% of total iron in meat, fish and poultry is in the heme form. Although the Monsen model can provide a generally good estimate of the heme iron content in animal products, recent research has suggested that the constant 40% value of heme iron is either an under- or over-estimation, depending on the source of the food. During this study a review was performed on the heme iron content of meat, fish and poultry, and comparisons are made with reference to the Monsen model. The aim of this study was to investigate whether using the constant 40% value for heme iron is adequate in describing the bio-availability of total iron in a particular food.  相似文献   

17.
刘胜杰  王艳平 《卫生研究》1995,24(6):361-364
膳食中铁的吸收利用受食物组成成分及烹调方法的影响。全素膳和基本素膳中铁是非血红素铁,与可利用铁之间呈显著负相关(r=-0.5480,P<0.001),其蛋白质与可利用铁之间也呈显著负相关(r=-0.8214,P<0.001),而每日添加100g左右瘦肉或肝的混合膳,因含有血红素铁和动物组织蛋白质,它们与可利用铁之间都呈显著正相关,分别为r=0.6488(P<0.001)和r=0.7579(P<0.001)。提示混合膳可提供足够的可利用铁以满足铁的需要,而素膳则不能。在无肉食的情况下,应改变烹调方法和饮食习惯,提高抗坏血酸的摄入量,以促进铁的利用。  相似文献   

18.
We used nationally representative data from the third National Health and Nutrition Examination Survey (NHANES III) to examine the relationship between low iron stores (serum ferritin < 12 microg/L) and dietary patterns that might affect iron status among Mexican American (MA) and non-Hispanic white (NHW) girls and women of reproductive age (12-39 y). Dietary data from the qualitative food-frequency questionnaire were used to classify subjects into three categories (using the 25th and 75th quartile values for NHW) for intake of heme iron, nonheme iron, iron absorption enhancers, and iron absorption inhibitors. The prevalence of low iron stores was 17.4% among MA (n = 1368) and 7.9% among NHW (n = 1473). Compared with high intake, the adjusted odds ratio (OR) for low iron stores was 1.80 [95% confidence interval (CI), 1.24-2.62] for medium intake of heme iron and 0.48 (95% CI, 0.25-0.91) for low intake of nonheme iron (plus iron supplement). Compared with no use, use of vitamin C supplements was associated with half the risk of low iron stores (OR = 0.50; 95% CI, 0.29-0.87). Similar results were found after income and parity were controlled for, except that the protective effect of vitamin C supplements was no longer significant. Even after adjustment for sociodemographic and dietary factors, MA women remained at increased risk for low iron stores (OR = 1.80; 95% CI, 1.30-2.49) indicating that the reasons for the higher prevalence of iron deficiency in MA women warrants further investigation.  相似文献   

19.
BACKGROUND: Adaptation of iron absorption in response to dietary iron bioavailability is less likely in premenopausal women, who generally have lower iron stores, than in men. OBJECTIVE: The objective of the study was to ascertain whether iron absorption in women adapts to dietary iron bioavailability and whether adaptation reflects altered absorptive efficiency or adjustment to specific inhibitors or enhancers of absorption. DESIGN: Heme- and nonheme-iron absorption from either high- or low-bioavailability diets was measured at 0 and 10 wk in premenopausal women as they consumed one of the diets for 12 wk (randomized 2 x 2 factorial design). The high- and low-bioavailability diets contained similar amounts of total iron, as 13.1 and 14.8 mg/d nonheme and 2.0 and 0.3 mg/d heme iron, respectively, and they differed in contents of meat, ascorbate, whole grains, legumes, and tea. RESULTS: In premenopausal women, the efficiency of nonheme-iron absorption (P = 0.06, two-tailed test), but not of heme-iron absorption, tended to adapt in response to a 12-wk difference in dietary iron bioavailability, whether absorption was tested with high- or low-bioavailability menus. Bioavailability, but not adaptation, substantially influenced total iron absorption (approximately 6-fold). In contrast with iron absorption from the low-bioavailability diet, that from the high-bioavailability diet consistently was inversely associated with serum ferritin. CONCLUSION: Only the high-bioavailability diet enabled women to absorb more iron in relation to their low iron stores. Women consuming the high-bioavailability diet absorbed up to 4.5 mg (30-35%) dietary iron with minimal influence of the diet consumed during the previous 10 wk.  相似文献   

20.
This study used two-day diet records to examine dietary behaviours in 504 Australian 18 year-olds in relation to gender, socio-economic status (SES) and national dietary guidelines. Fat intake exceeded 30% of energy in about 80% of subjects and was greater than 40% in about one-quarter. Saturated fat provided more than 10% of dietary energy in more than 90% of participants; less than 1% achieved a polyunsaturated to saturated fat ratio of at least one. The major food groups contributing to fat intake were convenience foods (32% in men, 28% in women) and meat (27% in men, 25% in women). Fibre intake was less than 30 g/day in 93% of women and 77% of men. Intakes of calcium, magnesium, potassium, and vitamins C and A, as a ratio of energy consumption, were greater in women than men, while sodium intake was significantly higher in men. Convenience foods were the greatest contributors to sodium intake (27% in men, 22% in women) followed by meat, bread, and soups and sauces. Greater consumption of cereals, fruit, vegetables and low-fat foods in young women of higher SES was reflected in their nutrient profile with higher intake of fibre and vitamin C and lower intake of fat. Men ate more cereals, meat and sugary foods and less fruit, vegetables and low-fat foods. Only 2.5% of men and 4.1% of women conformed with the health promotion message, widely publicised locally, to eat two fruits and five vegetables daily. Not eating breakfast was associated with lower calcium intake in men and women, and lower iron and fibre intake in women. Achieving behavioural changes in young adults must take into account differences in dietary behaviour related to gender and SES.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号