Dietary Fiber Intake Increases the Risk of Zinc Deficiency in Healthy and Diabetic Women

Phytic acid is a major determinant of zinc bioavailability. Little is known about phytic acid intakes or indices of zinc bioavailability in type 2 diabetes mellitus (DM), a condition that predisposes to zinc deficiency. The aim of this cross-sectional study was to measure and explore the relationships among phytic acid intake, zinc bioavailability, and molecular markers of zinc homeostasis in 20 women with DM compared to 20 healthy women. The phytate/zinc, (calcium)(phytate)/zinc, and (calcium + magnesium)(phytate)/zinc molar ratios were used to indicate zinc bioavailability. Plasma zinc concentrations and zinc transporter (ZnT1, ZnT8, and Zip1) gene expression in mononuclear cells were measured. Participants with DM consumed 1,194?±?824?mg/day (mean?±?SD) phytic acid, an amount similar to the intake of healthy women (1,316?±?708?mg/day). Bread products and breakfast cereals contributed more than 40?% of the phytic acid intake in each group. A positive relationship was observed in all participants between phytic acid and dietary fiber (r?=?0.6, P?<?0.001) and between dietary fiber and the (calcium)(phytate)/zinc ratio (r?=?0.5, P?<?0.001). Compared to the healthy group, the messenger RNA ratio of ZnT1 (zinc export) to Zip1 (zinc import) was lower in participants with DM, which may indicate perturbed zinc homeostasis in the disorder. The plasma zinc concentration was not predicted by age, body mass index, health status, zinc bioavailability, or zinc transporter expression. Healthy and diabetic women consume phytic acid in amounts that are likely to decrease the bioavailability of dietary zinc. Recommendations to consume greater amounts of dietary fiber, much of which is associated with phytate, increase the risk of zinc deficiency.     

Dietary molar ratios of phytate: Zinc and millimolar ratios of phytate × calcium: Zinc in South Koreans

The zinc nutritional status in south Koreans was established by evaluation of zinc, calcium and phytate intakes, the molar ratio of phytate: zinc, and the millimolar ratio of phytate × calcium: zinc. The intakes of iron and magnesium were also estimated. Sampling was designed so that it was representative of the national population. Two-day food records were used for the calculation of nutrient intakes, using food consumption data from the 1995 National Nutrition Survey (’95NNS) for South Korea. Daily intakes of zinc and calcium were estimated to be 10.1 mg/d and 426.5 mg/d, respectively, and those of iron and magnesium were 15.2 mg/d and 268.0 mg/d, respectively. The estimated daily phytate intake was 1676.6 mg/d. The ratio of phytate: zinc was 15.9 mol/d and that of phytate × calcium: zinc was 168.9 mmol/d. The ratio in millimoles per 4.2 MJ (1000 kcal) of phytate × calcium: zinc was 91.8. The major food groups for zinc intake were meat, poultry and their products (43%), and cereals and grain products (18%). Sixty-two percent of zinc was from animal food sources. Cereal and grain products supplied most of the phytate intake (46%) followed by seasonings, fruits, and legumes and their products. The major food source of phytate was rice (39%). The results of the study raise concern about the suboptimal zinc status in relation to the Western diet.     

Relevance of chronotype for eating patterns in adolescents

During adolescence, a shift from morningness to eveningness occurs, yet school continues to start early in the morning. Hence, adolescents are at risk for social jetlag, i.e. a discrepancy between biological and social timing. It remains to be determined whether chronotype associates with daily and daytime-specific eating patterns during this potentially critical period. Therefore, the aim of the present study was to investigate whether chronotype is decisive for daily eating patterns [total energy intake (TEI, kcal), total macronutrient intake (% of TEI), eating occasion frequency (n/day), meal frequency (n/day), snack frequency (n/day), duration of nightly fasting], or daytime-specific eating patterns [morning (before 11 am) energy intake (% of TEI), morning macronutrient intake (% of morning energy intake), regular breakfast skipping (no morning energy intake at least on 2 of 3?days, yes/no), evening (after 6 pm) energy intake (% of TEI), evening macronutrient intake (% of evening energy intake), regular dinner skipping (no evening energy intake at least on 2 of 3?days, yes/no)] in German adolescents. Chronotype was assessed by use of the Munich Chronotype Questionnaire and is defined as the midpoint of sleep corrected for sleep-debt accumulated over the workweek (the later the midpoint of sleep, the later the chronotype). A total of 223 participants (10–18?years) provided 346 questionnaires and concurrent 3-day weighed dietary records. Associations between chronotype and eating patterns were analyzed cross-sectionally using multivariable linear and logistic mixed-effects regression models. Adolescents with earlier and later chronotypes did not differ in their daily eating patterns. With respect to daytime-specific eating patterns, 1?h delay in chronotype was associated with 4.0 (95% CI 2.5–6.6) greater odds of regular breakfast skipping (p < 0.0001). In addition, later chronotype was associated with higher evening energy intake (p = 0.0009). In conclusion, our data show that a later chronotype among adolescents is associated with a shift of food consumption toward later times of the day. Hence, adolescents’ eating patterns appear to follow their internal clock rather than socially determined schedules.     

Dietary phytate × calcium/zinc millimolar ratios and zinc nutriture in some Ontario preschool children

Millimolar ratios of phytate/Zn, Ca x phytate/Zn, and Ca x phytate/Zn per 4.2 MJ were calculated from 3-d weighed-food records collected from 62 male (M) (mean age: 58 +/- 7 mo [mean +/- SD]) and 44 female (F) (mean age: 58 +/- 6 mo) preschool children from Southern Ontario. Food-composition values for phytate were based on laboratory analysis and the literature. No gender differences existed for median millimolar ratios of phytate/Zn (median: M, 5.3; F, 5.3), and Ca x phytate/Zn per 4.2 MJ (M, 68.1; F, 59.5), but median intakes of phytate (M, 399; F, 333 mg/d) and median millimolar ratios of Ca x phytate/Zn (median: M, 102.1; F, 72.3; p less than 0.01) were higher for boys than for girls. Of the children, only two (1M, 1F) and 22 (17 M, 5F) had millimolar ratios of phytate/Zn and Ca x phytate/Zn per 4.2 MJ, respectively, that were above critical values. Millimolar ratios of Ca x phytate/Zn (p = 0.06) and Ca x phytate/Zn per 4.2 MJ (p = 0.05) were higher in boys with hair zinc less than 1.07 mumol/g v greater than or equal to 1.07 mumol/g. Analysis of variance showed that height was influenced by an interaction between millimolar ratios of Ca x phytate/Zn per 4.2 MJ and sex (p = 0.0007), when age and midparent height were treated as covariates. Results suggest that dietary Ca x phytate/Zn millimolar ratios, when expressed per 4.2 MJ, influenced the zinc nutriture of these Southern Ontario boys.     

Indices of iron and copper status during experimentally induced,marginal zinc deficiency in humans

This study examined the effect of diet-induced, marginal zinc deficiency for 7 wks in 15 men (aged 25.3 +/- 3.3 yrs; mean +/- SD) on selected indices of iron and copper status. The regimen involved low-zinc diets based on egg albumin and soy protein with added phytate and calcium such that mean [phytate]/[Zn] and [phytate] X [Ca]/[Zn] molar ratios were 209 and 4116, respectively, for 1 wk, followed by 70 and 2000, respectively, for 6 wks. Subjects were then repleted with 30 mg Zn/d for 2 wks. Plasma copper, Cu,Zn-superoxide dismutase (Cu,Zn-SOD) activity in plasma and red blood cells (RBC), hemoglobin, hematocrit, and serum ferritin were determined weekly on fasting blood samples. Significant reductions (p less than 0.05) after 7 wks in RBC Cu,Zn-superoxide dismutase (49.5 +/- 7.2 vs 33.6 +/- 6.3 U/mg Hb) and serum ferritin (69.2 +/- 38.7 vs 53.8 +/- 33.7 micrograms/L) occurred; no comparable decline was noted for plasma Cu, hemoglobin, or hematocrit. Significant (p less than 0.05) but less consistent changes were also observed in plasma superoxide dismutase activity. None of the changes were associated with the decreases in plasma, urinary and hair zinc concentrations, and alkaline phosphatase activity in RBC membranes. Results indicate that the biochemical iron and copper status of the subjects was marginally impaired, probably from the dietary regimen that induced marginal zinc deficiency.     

Zinc Fractional Absorption from a Representative Diet in Young Chinese Men and Women of the Shandong Rural Region

The objective of this study was to investigate the zinc fractional absorption of young Chinese men and women from the Shandong rural region under the routine dietary pattern by stable isotope technique. Ten men and 10 women, aged 20 to 35 years, and with a representative diet during the experiment were recruited from the Shandong rural region. Stable ⁶⁷Zn was used as a tracer to label ZnCl₂, and Yb was used to monitor the excretion of ⁶⁷Zn in urine and feces. All volunteers were given rice containing 4.0 mg ⁶⁷Zn and 1.0 mg Yb on the fourth day. Then the food and fecal samples of all subjects were collected for 12 consecutive days. The total zinc and the stable zinc isotope ratio of all samples were determined by atomic absorption spectrophotometer and thermal ionization mass spectrometer, respectively. The determination of the other nutrients was performed based on the Chinese National Standard Methods. Among volunteers, the daily intake of zinc was 15.50 mg, 103.33 % of recommended nutrient intake (RNI, set by the Chinese Nutrition Society) in men and 15.43 mg, 134.17 % in women. The fractional absorption of Zn was 23.42 ± 2.23 % in men, and 22.49 ± 2.19 % in women. The protein candidates got from the typical diets was 93.96 % of RNI in women. Calcium and ascorbic acid intakes were 76.23 % of RNI and 27.91 % of RNI in men, respectively and 51.17 % of RNI and 34.23 % of RNI in women, respectively. Our results showed that a typical meal for someone in the Shandong rural region presented an adequate intake of zinc and a moderate Zn bioavailability. The shortage of protein and the inappropriate protein pattern may play important roles in reducing zinc bioavailability.     

Effects of Dinner Composition on Postprandial Macronutrient Oxidation in Prepubertal Girls

Objective: To see whether a fat‐rich (50%) evening meal promoted fat oxidation and a different spontaneous food intake on the following day at breakfast than a meal with a lower fat content (20%) in 10 prepubertal obese girls. Research Methods and Procedures: The postabsorptive and postprandial (10.5 hours) energy expenditure after a low‐fat (LF) (20% fat, 68% carbohydrate, 12% protein) and an isocaloric (2.1 MJ) and isoproteic high‐fat (HF; 50% fat, 38% carbohydrate, 12% protein) meal were measured by in direct calorimetry. Results: Fat oxidation was not significantly different after the two meals [LF, 31 ± 9 vs. HF, 35 ± 9 g/10.5 hours, p = not significant (NS)]. The girls oxidized 1.8 ± 0.9 times more fat than that ingested (11.1 grams) with the LF meal vs. 0.3 ± 0.3 times more fat than that ingested (27.1 grams) with the HF meal (p < 0.001). Carbohydrate oxidation was significantly higher after an LF than an HF meal (39 ± 12 vs. 29 ± 9 g/10.5 hours, p < 0, 05). At breakfast, the girls spontaneously ingested a similar amount of energy (1.5 ± 0.7 vs. 1.5 ± 0.6 MJ, p = NS) and macronutrient proportions (fat, 23% vs. 26%, p = NS; protein, 9% vs. 10%; carbohydrate, 68% vs. 64%,) independently of their having eaten an HF or an LF dinner. Discussion: An HF dinner did not stimulate fat oxidation, and no compensatory effect in spontaneous food intake was observed during breakfast the following morning. Cumulated total fat oxidation after dinner was higher than total fat ingested at dinner, but a much larger negative fat balance was observed after the LF meal. Spontaneous energy and nutrient intakes at breakfast were similar after LF and HF isocaloric, isoproteic dinners. This study points out the lack of sensitivity of short‐term fat balance to subsequently readjust fat intake and emphasizes the importance of an LF meal to avoid transient positive fat imbalance.     

Effects of phytate reduction,fat extraction,and level of Ca on Ca and Zn bioavailability

The effect of phytate reduction, fat extraction, and addition of Ca in the form of skim or whole milk on Ca and Zn bioavailability from a breakfast containing bran muffins was studied in vitro and in vivo. Ca and Zn solubility were measured after in vitro simulated peptic and pancreatic digestion under pH conditions resembling those in the human GI tract. Absorption of Ca and Zn was measured in rats fed test meals tagged with 45Ca and 65Zn. Radioactivity in the femur and liver relative to levels found in rats injected with the isotopes served as criteria for 45Ca and 65Zn absorption, respectively. In vitro solubility was significantly depressed by the presence of phytate and inversely correlated with the phytate:Zn and the (phytate)(Ca):(Zn) ratios. Ca solubility was enhanced by extraction of fat and markedly increased by reduction in both fat and phytate. None of these effects was seen in vivo. However, 65Zn absorption was significantly decreased by fat extraction and phytate reduction although this treatment increased in vitro Zn solubility. Possible reasons for these discrepancies are discussed.     

Usefulness of the dietary phytic acid/ zinc molar ratio as an index of zinc bioavailability to rats and humans

Evidence suggests that rats can tolerate a dietary phytate/Zn molar ratio greater than 15 if the dietary Zn concentration is high. High dietary Ca exacerbates the effect of phytic acid on Zn utilization by rats. In a short term (15 d) balance trial with adult men, we observed slightly greater Zn balance when whole compared to dephytinized wheat bran was consumed (molar ratios 12 and 1.2, respectively). There was, however, greater fecal excretion of Zn during the first 5 d whole bran was consumed. In a second study, Na phytate was the major source of phytic acid and Zn balance was less when the phytate/Zn molar ratio was greater than 16 compared to 4. The difference was not significant, however, and there was evidence of physiological adjustments to maintain homeostasis when the high ratio diet was consumed. Mean Zn intake averaged 17 mg (0.26 mmole) and 11 mg (0.17 mmole) daily for the bran and Na phytate studies, respectively. The level of Zn intake may influence the response of humans to varying phytate/Zn ratios. Comparison of isotope retention studies and the balance data is discussed. Some information on the relationship of dietary Ca to the phytate/Zn effect in human diets is gathered from current literature. The phytate/Zn molar ratio is a useful index of Zn bioavailability.     

Iodine Content of U.S. Weight-Loss Food

ObjectiveThe recommended iodine intake is 150 μg/ day in adults, 220 μg/day during pregnancy, and 290 μg/ day during lactation. Individuals exclusively consuming restricted diets as part of a weight-loss program may be at risk for mild to moderate iodine deficiency. The purpose of this study was to assess the iodine content in meals and snacks from 3 U.S. commercial weight-loss programs, all of which are intended to be the sole source of dietary intake during the desired weight-loss period.MethodsThe iodine contents in the products representing 1 week of all meals and snacks from 3 U.S. commercial weight-loss programs were measured by spectrophotometry. The measured total iodine content in 1 week’s worth of food from each program is reported as an average level per day.ResultsA total of 53 total items were analyzed (29 different items [7 breakfasts, 7 lunches, 7 dinners, 6 snacks, 2 desserts] from Jenny Craig®, 21 different items [7 breakfasts, 7 lunches, 7 dinners] from Nutrisystem®, and 3 different items [1 breakfast, 1 lunch, 1 dinner; each to be intended to be eaten daily for 1 week] from Medifast®). Daily iodine content (mean ± SD) of meals and snacks from the weight-loss programs were 34.2 ± 1.2 (Jenny Craig®), 12.2 ± 0.7 (Nutrisystem®), and 70.1 ± 1.1 (Medifast) μg/day.ConclusionThese results indicate that the dietary content in the foods from 3 U.S. commercial weight-loss programs is far less than the recommendations for iodine intake of 150 μg/day in nonpregnant, nonlactating adults. Individuals following each weight-loss program should be advised to take a multivitamin containing 150μg of iodine daily. (Endocr Pract. 2014;20:232-235)     

Absorption of zinc and retention of calcium: Dose-dependent inhibition by phytate

The dose-dependent inhibitory effect of sodium phytate (myo-inositol-hexaphosphate) on absorption of zinc and retention of calcium was studied in man. No systematic study of this dose-response effect has been reported to this time. Forty subjects were served meals containing white wheat rolls without/with additions of phytate. Ten subjects were given test meals containing one or two of the studied levels of phytate and in addition all subjects were served meals to which no phytate was added. The zinc content was 3.1 mg (47 micromol) and the calcium content 266 mg (6.6 mmol). The rolls were labelled extrinsically with radioisotopes, 65Zn and 47Ca, and whole-body retention of both minerals was measured. Totally 105 meals were served, 36 meals in which no phytate was added and 9-10 meals on each level of phytate. The zinc absorption in meals to which either 0, 25, 50, 75, 100, 140, 175 or 250 mg of phytate-P (0, 134, 269, 403, 538, 753, 941 or 1344 micromol phytate) had been added was 22%, 16%, 14%, 11%, 7%, 7%, 7% and 6%, respectively (mean values). The addition of 50 mg phytate-P or more significantly decreased zinc absorption (p=0.01) as compared to absorption from the test meals with no added phytate. The calcium retention at day 7 in the same meals was 31%, 28%, 27%, 26%, 22%, 19%, 14% and 11% (mean values). The addition of 100 mg phytate-P or more significantly decreased calcium retention (p=0.03) compared to the test meals with no added phytate. It was concluded that the inhibitory effect of phytate on the absorption of zinc and the retention of calcium was dose dependent.     

Dietary and Non-dietary Factors Associated with Serum Zinc in Indian Women

Women in low-income settings, common in India, are at risk of inadequate zinc intake due to poor diet quality and low consumption of flesh foods rich in zinc. The aims of this study were to assess the prevalence of zinc status of non-pregnant rural and tribal women living in central India and to identify dietary and non-dietary factors associated with the biochemical zinc status of these women. Rural and tribal non-pregnant women 18–30 years of age were selected using proportion to population sampling near Nagpur, Maharashtra, India. Sociodemographic, biochemical (serum zinc), clinical, and dietary data (1-day interactive 24-h recall) were collected. The mean age of women (n?=?109; rural?=?52; tribal?=?56) was 23.2 years and mean BMI was 17.9 kg/m². The majority of the participants identified as being non-vegetarian (72 %). The mean?±?SD serum zinc concentration was 10.8?±?1.6 μmol/L, and 52 % of participants had a low serum zinc concentration according to the International Zinc Nutrition Consultative Group (IZiNCG). The median (first and third quartile) energy, zinc intake, and phytate/zinc molar ratio was 5.4 (4.2, 6.7)?MJ/day, 5.3 (3.8, 7.0)?mg/day, and 26 (22, 28), respectively. Zinc intakes were well below IZiNCG recommendations for dietary zinc of 9 mg/day for non-pregnant women aged 14–18 years and 7 mg/day for non-pregnant women aged ≥19 years. Using linear regression analysis to identify non-dietary and dietary factors associated with serum zinc, a significant association was only found for current lactation (p?=?0.012) and energy intake (p?相似文献   

Iron Dialyzability from Hospital Duplicate Meals: Daily Intake

Both total and dialyzable iron levels and corresponding dialyzability were determined in 108 duplicate meals during 36 consecutive days. Total mean iron fraction of 5.90 ± 4.97 mg was found in the meals. The iron supplied by the meals is directly and significantly (p < 0.05) correlated with macromicronutrient content (carbohydrates, fiber, and protein). The mean iron dialyzability (4.81 ± 3.25%) was low and not significantly different among the three primary meals (breakfast, lunch, and dinner). Significant interactions of several minerals on iron levels were found (p < 0.05). Iron dialyzability was only statistically influenced by zinc dialyzability in meals (p < 0.05). The dialyzed iron fraction present in meals was significantly correlated with protein and ascorbic acid levels (p < 0.01). The mean iron daily dietary intake was 17.7 ± 6.91 mg. The hospital meals provided enough iron. Foods of animal origin are primary sources of iron in diet.     

Energy Metabolism in Rat Brain Synaptosomes from Nembutal-Anesthetized and Nonanesthetized Animals

Abstract: Cellular energetic parameters including the intramitochondrial and cytosolic [NAD⁺]/[NADH] ratios, the cellular [ATP]/[ADP][P_i and [creatine phosphate]/[creatine] ratios, the concentration of cytochrome c and its redox state and the respiratory rate were studied in suspensions of rat brain synapto-somes isolated from nembutal-anesthetized and nonanesthetized animals. The ratio of [3-hydroxybutyrate] to [acetoacetate] was 2.0 in synaptosomes isolated from nonanesthetized rats and 5.55 in those from anesthetized animals. The [lactate]/[pyruvate] ratio was 3.8 in the former and 10.9 in the latter preparation. The [ATP]/[ADP][P_i] was 3838 M⁻¹ in the synaptosomes from anesthetized rats and 840 M⁻¹ in those from nonanesthetized animals and the [creatine phosphate]/[creatine] ratios were 0.79 and 0.39, respectively. Cytochrome c was about 15% reduced in both preparations; however, the mitochon-drial cytochrome concentration was almost twofold higher in the synaptosomes from nonanesthetized animals. Calculations of the free energy relationships between the mitochondrial redox reactions and ATP synthesis showed that in synaptosomes isolated from the brains of nembutal-anesthetized rats the first two sites of oxidative phosphorylation were at near-equilibrium, in agreement with observations for intact cells and tissues. The energetic parameters for synaptosomes from anesthetized rats are very similar to the values for intact whole brain, whereas those for synaptosomes from nonanesthetized rats are lower and suggest that nembutal anesthesia protects against some irreversible damage to the synaptosome during isolation. It is concluded that synaptosomes isolated from brains of nembutal-anesthetized rats can be used as a convenient model system for studies of neuronal metabolism.     

Mineral intakes of predominantly lacto-ovo vegetarian East Indian adults

Daily energy, protein, calcium (Ca), phosphorus (P), zinc (Zn), copper (Cu), manganese (Mn), and dietary fiber intakes of East Indian Punjabi immigrants consuming predominantly lacto-ovo vegetarian diets [59 males (M), mean age 37.7±10.5 yr. and 53 females (F), mean age 33.3±7.4 yr] were assessed by calculation from 3-d weighted dietary records, using food composition values and by chemical analysis of 30 1-d diet composites. Mean daily calculated intakes wer: energy, M=2374±713 and F=1708±552 kcal; protein, M=95.8±35.1 and F=68.0±28.9g; Ca, M=990±468 and F=837±393 mg; M=2034±778 and F=1489±551 mg; Zn, M=12.2±4.9 and F=8.8±3.9 mg; Cu, M=2.4±0.9 and F=1.7±0.6 mg; and Mn, M=7.7±3.3 and F=5.7±2.4 mg. The mean daily Ca intakes for M and F were 124 and 105%, respectively, of the Canadian Recommended Nutrient Intake (RNI). In contrast, average P intakes were much higher, 254 and 213% of the RNI for M and F, respectively, so that the mean Ca:P ratios were 1:2.0 for M and 1:1.8 for F. Forty-eight percent of the F compared to 19% of the M had Zn intakes below the current RNI, whereas 28% of the M and 77% of the F received Cu intakes below the suggested US safe and adequate range. Mean daily Mn intakes were higher than those for subjects consuming omniverous North American diets and none of the subjects had Mn intakes below the US safe and adequate range.     

The individual and combined effects of glycemic index and protein on glycemic response, hunger, and energy intake

Although high protein and low glycemic index (GI) foods are thought to promote satiety, little is known about the effects of GI, protein, and their interaction on hunger and energy intake several hours following a mixed meal. This study investigated the long term effects of GI, protein, and their combined effects on glucose, insulin, hunger, and energy intake in healthy, sedentary, overweight, and obese adults (BMI of 30.9 ± 3.7 kg/m²). Sixteen individuals participated separately in four testing sessions after an overnight fast. The majority (75%) were non‐Hispanic Blacks. Each consumed one of four breakfast meals (high GI/low protein, high GI/high protein, low GI/low protein, low GI/high protein) in random order. Visual analog scales (VAS) and blood samples were taken at baseline, 15 min, and at 30 min intervals over 4 h following the meal. After 4 h, participants were given the opportunity to consume food ad libitum from a buffet style lunch. Meals containing low GI foods produced a smaller glucose (P < 0.002) and insulin (P = 0.0001) response than meals containing high GI foods. No main effects for protein or interactions between GI and protein were observed in glucose or insulin responses, respectively. The four meals had no differential effect on observed energy intake or self‐reported hunger, satiety, and prospective energy intake. Low GI meals produced the smallest postprandial increases in glucose and insulin. There were no effects for GI, protein, or their interaction on appetite or energy intake 4 h after breakfast.     

Studies on zinc bioavailability from a representative diet in Chinese urban women of childbearing age using a double label stable isotope technique

The objectives of the study were to determine dietary zinc bioavailability by using a double label stable isotope technique, and to identify the zinc content and levels of some possible factors which may affect zinc utilization in a typical representative Chinese urban diet. Twenty urban women of childbearing age were fed a diet extrinsically labeled with 67Zn and received intravenous (i.v.) injections of 70Zn. Fecal monitoring, urine monitoring and chemical balance technique were used simultaneously for comparisons. Isotopic enrichment in feces and urine after oral and i.v. administration of stable zinc isotopes was measured to determine the ways of zinc absorption. The mean (+/-SD) zinc intake from the representative Chinese diet was 10.22+/-0.80 mg/day, which is lower than the reference nutrient intake (RNI) level (11.5 mg/day), and mainly came from the subsidiary foods (63%). The mean dietary Fe/Zn weight was 1.1+/-0.1. The phytate/zinc molar ratio in the diet was about 3:1. The phytic acidxCa/zinc molar ratio in the diet was about 45:1. The apparent and true absorption rates of 67Zn were 36.2+/-9.7% and 38.2+/-10.1%, respectively, which were higher than the apparent absorption determined by balance technique (29.7+/-10.6%). The mean fractional absorption (FA) determined in urine was 35.7+/-13.3. In conclusion, the subsidiary food is the main source of dietary zinc in this typical diet. The extrinsic labeling technique by use of stable isotopes was more reliable and accurate to determine zinc absorption. Moreover, the double isotopic tracer ratio (DITR) technique applied to urine samples was a more practical and valuable way to evaluate zinc absorption than other methods. It can be speculated that iron and phytic acid might not be the main inhibitors in the representative Chinese diet.     

Calcium exacerbates the inhibitory effects of phytic acid on zinc bioavailability in rats

BackgroundComplementary feeding of breastfed infants with foods high in bioavailable zinc (Zn) can help meet physiological requirements for Zn. Some infant cereals contain high concentrations of phytic acid (PA) and calcium (Ca) that may reduce absorbable Zn.ObjectivesThis study measured PA, Zn and Ca concentrations in selected infant cereals sold in Canada and investigated the effects of dietary PA and Ca at concentrations present in infant cereals on Zn bioavailability in rats.Methods and resultsMale Sprague-Dawley rats (36-day old) were fed a control diet containing normal Zn (29.1 mg/kg) and Ca (4.95 g/kg) or six test diets (n = 12/diet group). Test diets were low in Zn (8.91–9.74 mg/kg) and contained low (2.16–2.17 g/kg), normal (5.00–5.11 g/kg) or high (14.6–14.9 g/kg) Ca without or with added PA (8 g/kg). After 2 weeks, rats were killed and Zn status of the rats was assessed. PA, Zn and Ca concentrations in infant cereals (n = 20) differed widely. PA concentrations ranged from undetectable to 16.0 g/kg. Zn and Ca concentrations ranged from 7.0–29.1 mg/kg and 0.8–13.4 g/kg, respectively. The [PA]/[Zn] and [PA × Ca]/[Zn] molar ratios in infants cereals with detectable PA (16 of 20 cereals) ranged from 22–75 and 0.9–14.9 mol/kg, respectively, predicting low Zn bioavailability. Body weight, body composition (lean and fat mass), right femur weight and length measurements and Zn concentrations in serum and femur indicated that diets higher in Ca had a more pronounced negative effect on Zn status of rats fed a PA-supplemented diet. Addition of PA to the diet had a greater negative effect on Zn status when Ca concentration in the diet was higher.ConclusionThese results show that, in rats, higher concentrations of dietary Ca and PA interact to potentiate a decrease in bioavailable Zn and may suggest lower Zn bioavailability in infant cereals with higher PA and Ca concentrations.     

Lower Zinc Bioavailability May Be Related to Higher Risk of Subclinical Atherosclerosis in Korean Adults

Background

There is a proposed link between dietary zinc intake and atherosclerosis, but this relationship remains unclear. Phytate may contribute to this relationship by influencing zinc bioavailability.

Objective

The aim of this study is to examine the relationship between zinc bioavailability and subclinical atherosclerosis in healthy Korean adults.

Materials and Methods

The present cross-sectional analysis used baseline data from the Korean multi-Rural Communities Cohort Study (MRCohort), which is a part of The Korean Genome Epidemiology Study (KoGES). A total of 5,532 subjects (2,116 men and 3,416 women) aged 40 years and older were recruited from rural communities in South Korea between 2005 and 2010. Phytate:zinc molar ratio, estimated from a food-based food frequency questionnaire (FFQ) of 106 food items, was used to determine zinc bioavailability, and carotid intima media thickness (cIMT) and pulse wave velocity (PWV) were measured to calculate the subclinical atherosclerotic index.

Results

We found that phytate:zinc molar ratio is positively related to cIMT in men. A higher phytate:zinc molar ratio was significantly related to an increased risk of atherosclerosis in men, defined as the 80^th percentile value of cIMT (5^th vs. 1^st quintile, OR = 2.11, 95% CI 1.42-3.15, P for trend = 0.0009), and especially in elderly men (5^th vs. 1^st quintile, OR = 2.58, 95% CI 1.52-4.37, P for trend = 0.0021). We found a positive relationship between phytate:zinc molar ratio and atherosclerosis risk among women aged 65 years or younger. Phytate:zinc molar ratio was not found to be related to PWV.

Conclusions

Lower zinc bioavailability may be related to higher atherosclerosis risk.     

Eating Frequency is Associated With Energy Intake but Not Obesity in Midlife Women

Midlife women tend to gain weight with age, thus increasing risk of chronic disease. The purpose of this study was to examine associations between overweight/obesity and behavioral factors, including eating frequency, in a cross‐sectional national sample of midlife women (n = 1,099) (mean age = 49.7 years, and BMI = 27.7 kg/m²). Eating behaviors and food and nutrient intakes were based on a mailed 1‐day food record. BMI was calculated from self‐reported height and weight, and level of physical activity was assessed by self‐reported questionnaire. After exclusion of low‐energy reporters (32% of sample), eating frequency was not associated with overweight/obesity (P > 0.05) and was not different between BMI groups (normal, 5.21 ± 1.79; overweight, 5.16 ± 1.74; obese, 5.12 ± 1.68, P = 0.769). Adjusted logistic regression showed that eating frequency, snacking frequency, breakfast consumption, eating after 10 pm and consuming meals with children or other adults were not significantly associated with overweight/obesity. Total energy intake increased as eating frequency increased in all BMI groups, however, obese women had greater energy intake compared to normal weight women who consumed the same number of meals and snacks. Intake of fruit and vegetables, whole grains, dietary fiber, dairy, and added sugars also increased as eating frequency increased. While eating frequency was not associated with overweight/obesity, it was associated with energy intake. Thus, addressing total energy intake rather than eating frequency may be more appropriate to prevent weight gain among midlife women.