Phytate intake and molar ratios of phytate to zinc, iron and calcium in the diets of people in China.
To assess the phytate intake and molar ratios of phytate to calcium, iron and zinc in the diets of people in China.
2002 China Nationwide Nutrition and Health Survey is a cross-sectional nationwide representative survey on nutrition and health. The information on dietary intakes was collected using consecutive 3 days 24 h recall by trained interviewers.
The data of 68 962 residents aged 2-101 years old from 132 counties were analyzed.
The median daily dietary intake of phytate, calcium, iron and zinc were 1186, 338.1, 21.2 and 10.6 mg, respectively. Urban residents consumed less phytate (781 vs 1342 mg/day), more calcium (374.5 vs 324.1 mg/day) and comparable amounts of iron (21.1 vs 21.2 mg/day) and zinc (10.6 vs 10.6 mg/day) than their rural counterparts. A wide variation in phytate intake among residents from six areas was found, ranging from 648 to 1433 mg/day. The median molar ratios of phytate to calcium, iron, zinc and phytate x calcium/zinc were 0.22, 4.88, 11.1 and 89.0, respectively, with a large variation between urban and rural areas. The phytate:zinc molar ratios ranged from 6.2 to 14.2, whereas the phytate x calcium/zinc molar ratios were from 63.7 to 107.2. The proportion of subjects with ratios above the critical values of phytate to iron, phytate to calcium, phytate to zinc and phytate x calcium/zinc were 95.4, 43.7, 23.1 and 8.7%, respectively. All the phytate/mineral ratios of rural residents were higher than that of their urban counterparts.
The dietary phytate intake of people in China was higher than those in Western developed countries and lower than those in developing countries. Phytate may impair the bioavailability of iron, calcium and zinc in the diets of people in China.
Iron overload inhibits osteoblast biological activity through oxidative stress.
Iron overload has recently been connected with bone mineral density in osteoporosis. However, to date, the effect of iron overload on osteoblasts remains poorly understood. The purpose of this study is to examine osteoblast biological activity under iron overload. The osteoblast cells (hFOB1.19) were cultured in a medium supplemented with different concentrations (50, 100, and 200 μM) of ferric ammonium citrate as a donor of ferric ion. Intracellular iron was measured with a confocal laser scanning microscope. Reactive oxygen species (ROS) were detected by 2,7-dichlorofluorescin diacetate fluorophotometry. Osteoblast biological activities were evaluated by measuring the activity of alkaline phosphatase (ALP) and mineralization function. Results indicated that iron overload could consequently increase intracellular iron concentration and intracellular ROS levels in a concentration-dependent manner. Additionally, ALP activity was suppressed, and a decline in the number of mineralized nodules was observed in in vitro cultured osteoblast cells. According to these results, it seems that iron overload probably inhibits osteoblast function through higher oxidative stress following increased intracellular iron concentrations.
He YF, Ma Y, Gao C, Zhao GY…
Biol Trace Elem Res May 2013 PMID: 23334864
A comparison of the biological activities of human osteoblast hFOB1.19 between iron excess and iron deficiency.
Bone metabolism has a close relationship with iron homeostasis. To examine the effects of iron excess and iron deficiency on the biological activities of osteoblast in vitro, human osteoblast cells (hFOB1.19) were incubated in a medium supplemented with 0-200 μmol/L ferric ammonium citrate and 0-20 μmol/L deferoxamine. The intracellular iron was measured by a confocal laser scanning microscope. Proliferation of osteoblasts was evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Apoptotic cells were detected using annexin intervention V/PI staining with a flow cytometry. Alkaline phosphatase (ALP) activity was measured using an ALP assay kit. The number of calcified nodules and mineral area was evaluated by von Kossa staining assay. The expressions of type I collagen and osteocalcin of cultured osteoblasts were detected by reverse transcriptase polymerase chain reaction and Western blot. Intracellular reactive oxygen species (ROS) was measured using the oxidation-sensitive dye 2,7-dichlorofluorescin diacetate by flow cytometry. The results indicated that excessive iron inhibited osteoblast activity in a concentration-dependent manner. Low iron concentrations, in contrast, produced a biphasic manner on osteoblasts: mild low iron promoted osteoblast activity, but serious low iron inhibited osteoblast activity. Osteogenesis was optimal in certain iron concentrations. The mechanism underlying biological activity invoked by excessive iron may be attributed to increased intracellular ROS levels.
Zhao GY, Zhao LP, He YF, Li GF…
Biol Trace Elem Res Dec 2012 PMID: 23054865
Hemochromatosis is an iron overload disorder associated with osteopenia and osteoporosis. To learn more about the effects of iron on bone cells, we examined the effects of ferric ion on the proliferation, differentiation, and mineralization of two types of cultured osteoblasts, the cell line MC3T3-E1 and rat calvarial osteoblast-like (ROB) cells. We used ferric ammonium citrate (FAC) as a donor of ferric ion, and FAC inhibited the proliferation of MC3T3-E1 cells in a dose-dependent manner. FAC (0.1-1 microg/ml) inhibited indices of osteoblast differentiation, such as the expression of type I collagen (mRNA and protein), the activity of alkaline phosphatase, and the deposition of calcium by osteoblasts. These results suggest that iron overload might give rise to osteoporosis by inhibiting osteoblast proliferation and differentiation.
Iron deficiency negatively affects vertebrae and femurs of rats independently of energy intake and body weight.
The question of whether iron deficiency has direct adverse effects on vertebral trabecular bone and long bones was answered by this study. Four groups of female weanling rats were fed for 5 wk diets that were 1) control; 2) calcium restricted, 1.0 g Ca/kg diet; 3) iron deficient, <8 mg Fe/kg diet; or 4) control, pair-fed to the iron-deficient group. Whole body and femur DEXA analysis revealed that calcium-restricted and iron-deficient rats had lower bone mineral density (BMD) and content (BMC) than pair-fed and control rats. However, pair-fed rats also had decreased BMD and BMC compared to control rats. The third lumbar trabecular bone microarchitecture in both diet-restricted groups had decreased bone volume fraction (BV/TV) and trabecular number and thickness, a less favorable structural model index, and increased trabecular separation compared with the controls and the pair-fed groups as determined by microcomputer tomography. The control and pair-fed groups did not differ from one another, suggesting that iron deficiency and calcium restriction affected vertebrae independently of food intake and body weight. Finite element analysis revealed lower force to compress the vertebrae and lower stiffness but greater von Mises stress in calcium-restricted and iron-deficient groups compared to the control and pair-fed groups. Urinary deoxypyridinium crosslinks, serum osteocalcin, and cholcalciferol were increased in calcium-restricted rats compared to the other 3 groups. Using micro-CT imaging technology, this study demonstrated microarchitectural pathology due to iron deficiency upon vertebral trabecular bone compared to the control and pair-fed rats, although not to the same extent as severe calcium restriction.
Iron status and its relations with oxidative damage and bone loss during long-duration space flight on the International Space Station.
Increases in stored iron and dietary intake of iron during space flight have raised concern about the risk of excess iron and oxidative damage, particularly in bone.
The objectives of this study were to perform a comprehensive assessment of iron status in men and women before, during, and after long-duration space flight and to quantify the association of iron status with oxidative damage and bone loss.
Fasting blood and 24-h urine samples were collected from 23 crew members before, during, and after missions lasting 50 to 247 d to the International Space Station.
Serum ferritin and body iron increased early in flight, and transferrin and transferrin receptors decreased later, which indicated that early increases in body iron stores occurred through the mobilization of iron to storage tissues. Acute phase proteins indicated no evidence of an inflammatory response during flight. Serum ferritin was positively correlated with the oxidative damage markers 8-hydroxy-2′-deoxyguanosine (r = 0.53, P < 0.001) and prostaglandin F2α (r = 0.26, P < 0.001), and the greater the area under the curve for ferritin during flight, the greater the decrease in bone mineral density in the total hip (P = 0.031), trochanter (P = 0.006), hip neck (P = 0.044), and pelvis (P = 0.049) after flight. Increased iron stores may be a risk factor for oxidative damage and bone resorption.
Zwart SR, Morgan JL, Smith SM
Am. J. Clin. Nutr. Jul 2013 PMID: 23719548
[Validation of questionnaires for the study of food habits and bone mass].
The loss of bone mass and density is influenced by nutritional factors that act on the bone mass peak, age-related bone loss and muscle strength. The objective of the present study was to validate a food frequency questionnaire applied to estimate the relationship between food habits and bone mineral density (BMD) in a healthy adult population.
The results of the food frequency questionnaire were compared with 24-hr recall findings. Calcaneus BMD was measured by densitometry.
The validity of the questionnaire was demonstrated, with Spearman correlation coefficients of 0.014 to 0.467. The Bland-Altman test also found no differences in study variables between the two methods. Correlation analysis showed that the BMD was significantly associated with the intake of vitamin D, vitamin A, vitamin B12, folate, thiamine and iron. Total fat consumption was not associated with BMD but the intake of monounsaturated fatty acids, EPA, DHA and cholesterol showed a significant correlation.
The questionnaire evaluates the consumption of energy and nutrients with adequate validity. Its application revealed the importance for bone health of a diet rich in B-group vitamins, vitamin D, calcium, iron, monounsaturated fatty acids and n-3.