Zinc and copper bioavailability in monkeys and rats with psyllium consumption

Adjustments in intestinal absorption and losses of zinc (Zn) are thought to maintain Zn homeostasis when dietary intake levels are altered. Zn status may also influence efficiency of intestinal Zn absorption. To determine the impact of dietary intake and status of some micronutrients on Zn absorption in late middle-aged men. Dietary intake and status of Zn, Cu, Fe, vitamin A, C and fibre, and absorption of Zn were measured in 48 men, aged 58-68 y, confined to a metabolic unit and consuming a typical French diet. Dietary intake was estimated using 4-day food-intake records (including the weekend) and the GENI program. To assess Zn status, serum, erythrocyte, urine Zn levels and serum alkaline phosphatase activity were determined. Zn absorption was determined using the isotope double-labelling method. Zn stable isotopic ratios were measured in plasma samples collected before and 48 h after isotope administration using ICP/MS. Zn intake within the group of men varied from 5.7 to 20.5 mg/day and averaged 12.9 mg/day. Serum Zn level varied from 10 to 18 micromol/l and averaged 12.9 micromol/l. Zn absorption varied from 12 to 46% and averaged 29.7%. Zn absorption was not significantly (P > 0.05) correlated with Zn intake or with any of the Zn status parameters. Zn absorption was only slightly negatively correlated with serum and erythrocyte Zn levels and with serum Fe and ferritin levels in this study. Zn dietary intake and Zn absorption were satisfactory and led to an adequate Zn status in this population.

Different metabolic pathways of supplemental and fortification Fe, or inhibition of Zn absorption by Fe, may explain adverse effects of supplemental Fe in Fe-sufficient infants. We determined whether the mode of oral Fe administration or the amount habitually consumed affects Fe absorption and systemic Fe utilisation in infants, and assessed the effects of these interventions on Zn absorption, Fe and Zn status, and growth. Fe-sufficient 6-month-old infants (n 72) were randomly assigned to receive 6·6 mg Fe/d from a high-Fe formula, 1·3 mg Fe/d from a low-Fe formula or 6·6 mg Fe/d from Fe drops and a formula with no added Fe for 45 d. Fractional Fe absorption, Fe utilisation and fractional Zn absorption were measured with oral (57Fe and 67Zn) and intravenous (58Fe and 70Zn) isotopes. Fe and Zn status, infection and growth were measured. At 45 d, Hb was 6·3 g/l higher in the high-Fe formula group compared with the Fe drops group, whereas serum ferritin was 34 and 35 % higher, respectively, and serum transferrin 0·1 g/l lower in the high-Fe formula and Fe drops groups compared with the low-Fe formula group (all P<0·05). No intervention effects were observed on Fe absorption, Fe utilisation, Zn absorption, other Fe status indices, plasma Zn or growth. We concluded that neither supplemental or fortification Fe nor the amount of Fe habitually consumed altered Fe absorption, Fe utilisation, Zn absorption, Zn status or growth in Fe-sufficient infants. Consumption of low-Fe formula as the only source of Fe was insufficient to maintain Fe stores.

Effects of silencing or overexpression of ZIP3 and ZIP5 on zinc absorption as zinc sulfate or zinc proteinate and related gene expressions in primary duodenal epithelial cells of broilers.

A total of 360 pigs (initially 6.0 ± 0.74 kg) were used to evaluate the effects of increasing dietary Zn in low acid-binding capacity at a pH of 4 (ABC-4) diets on nursery pig performance, fecal dry matter (FDM), and Zn status. At weaning, pigs were randomly assigned within two body-weight blocks to one of the six dietary treatments in a generalized randomized block design. There were five pigs per pen and 12 pens per treatment. Experimental diets were fed for 24-d, and then pigs were fed a common diet for 22 d. All diets contained 110 ppm of Zn from ZnSO4 from the trace mineral premix. The control treatment was a low-ABC-4 diet (200 and 250 meq/kg from d 0 to 10 and d 10 to 24, respectively). In the next four treatments, Zn levels were increased to 500, 1,000, 2,000, and 3,000 ppm in phase 1, and 333, 666, 1,332, and 2,000 ppm in phase 2 using ZnO. The sixth treatment was a high-ABC-4 diet (493 and 470 meq/kg from d 0 to 10 and d 10 to 24, respectively) with 3,000 and 2,000 ppm of Zn from ZnO from d 0 to 10 and d 10 to 24, respectively. Fecal samples were collected at d 10 and 24 to determine FDM. In all periods, no differences (P&amp;gt;0.10) were observed between the low- and high-ABC-4 diets when 3,000 and 2,000 ppm of Zn were added in phases 1 and 2, respectively, except for d-10 FDM, where the low-ABC-4 diet improved (P=0.002) FDM at the same Zn concentration. For the experimental period, ADG and ADFI increased (linear, P&amp;lt; 0.05) as dietary Zn increased, with no differences in G:F. For the overall period, no response (P&amp;gt;0.10) to dietary Zn was observed for any of the performance criteria. No dietary Zn effect was observed in the low-ABC-4 diets for FDM at d-10 or 24. Zinc intake, fecal excretion, and absorption increased (quadratic, P&amp;lt; 0.001) and apparent total tract digestibility (ATTD) of Zn tended to increase (linear, P=0.074) with increasing dietary Zn. The low-ABC-4 diet had greater (P&amp;lt; 0.05) Zn intake, absorption, and ATTD of Zn than the high-ABC-4 diet at the same Zn concentration. No difference was observed for fecal Zn excretion between ABC-4 formulation strategies. Day 24 serum Zn concentration increased (quadratic, P&amp;lt; 0.001) as dietary Zn increased, and a marginal increase (P=0.095) in favor of the low-ABC-4 diets was observed between formulation strategies. In conclusion, low ABC-diets containing 3,000 and 2,000 ppm of Zn from ZnO in phases 1 and 2, respectively, increased d-10 fecal DM, Zn absorption, and ATTD of Zn. Increasing ZnO in low-ABC-4 diets improved ADG and ADFI during the experimental period, but not overall.

1. A method of studying zinc absorption in rats has been developed in which binding of radioactive Zn to the intestinal mucosa and absorption into the carcass was determined at different times after administration by stomach tube. 2. This technique has been used to evaluate different hypotheses concerning the control of Zn absorption and to examine the processes by which this occurs. 3. The proportion of radioactive Zn absorbed into the carcass was found to be dependent on the Zn status of the animals but that found within the small intestinal wall was independent of this, indicating the existence of two mechanisms of Zn absorption. 4. One of these two mechanisms has been shown to be induced by a low dietary Zn content while the other was shown to be insensitive to this. This latter mechanism predominated in rats of normal dietary Zn, status and a study of the characteristics of this process indicated that the quantity of Zn absorbed was proportional to the dietary Zn content over the normal range of intake. This implies that normally Zn homeostasis in rats is achieved through variations in Zn excretion. The additional mechanism of Zn absorption only becomes fully active at levels of dietary Zn below 0.24 MUMOL/g diet.

Intestinal Metallothionein Gene Expression and Zinc Absorption in Rats Are Zinc-Responsive but Refractory to Dexamethasone and Interleukin 1α

The addition of 1 g sugar-beet fibre (Beta Fibre) to 3 g semi-synthetic diet resulted in a 54% increase in iron and a 39% increase in zinc absorption in rats. The same amount of non-starch polysaccharides fed as wheat bran (1.9 g) had no effect on Fe absorption but reduced Zn absorption by 9%. The inhibitory effect of wheat brain is probably due to its high phytate content, but there is, as yet, no explanation for the enhancement of Fe and Zn absorption caused by Beta Fibre. If the effect also occurs in man, it will have important implications for high-fibre diets and mineral nutrition.

No study is currently available regarding the roles of the amino acid transporters in promoting mineral absorption in animals. To study whether the y(+)L-type amino acid transporter 2 (y+LAT2) participates in enhancing Zn absorption as Zn proteinate with moderate chelation strength (Zn-Prot M) in broilers, three experiments were carried out to investigate the effects of y+LAT2 silencing and overexpression on zinc (Zn) absorption as Zn-Prot M and related gene expressions in broiler primary duodenal epithelial cells (BPDECs) contrasted with Zn sulfate (ZnSO4). In experiment 1, three pairs of siRNAs (si-494, si-834, and si-1153) targeting y+LAT2 were synthesized and transfected within the cells to identify the optimal siRNA for silencing y+LAT2 mRNA expression, and the data were analyzed by one-way ANOVA. In experiment 2, cells were incubated for 2 h in either a DMEM/F12 complete medium without Zn supplementation (Control) or the same medium enriched with 400 μmol Zn/liter as ZnSO4 or Zn-Prot M, with or without the only one effective siRNA targeting y+LAT2, and the data were analyzed by two-way ANOVA. In experiment 3, with or without the recombinant adenovirus plasmid encoding y+LAT2, cells were also treated for 2 h with the same media as in experiment 2, and the data were analyzed by two-way ANOVA. The results demonstrated that in experiment 1, the si-494 was the only one effective (P < 0.0001) siRNA for inhibiting y+LAT2 mRNA expression. In experiment 2, y+LAT2 silencing reduced its own mRNA and protein abundances (P < 0.0001) by 46% and 14% and Zn absorption from Zn-Prot M by 34% (P < 0.05), with no effect (P > 0.05) on Zn absorption from ZnSO4. In experiment 3, y+LAT2 overexpression elevated its own mRNA and protein expressions by 949% and 18% (P < 0.0001) and Zn absorption from Zn-Prot M by 73% (P < 0.05), but didn’t affect (P > 0.05) Zn absorption from ZnSO4. Additionally, Zn-Prot M upregulated (P < 0.05) the y+LAT2 protein expression compared to the Control and ZnSO4 by 12 to 17%, with no impact (P > 0.07) on the y+LAT2 mRNA expression, regardless of y+LAT2 silencing or overexpression. In conclusion, the y+LAT2 took part in promoting Zn absorption as Zn-Prot M in BPDECs.

To evaluate Zn utilization and status among a sample of Spanish boys consuming a diet based on Mediterranean patterns. Dietary Zn balance was assessed by means of Zn intake in food and Zn output in faeces and urine as measured by flame atomic absorption spectrophotometry. In addition, biomarkers of Zn status were analysed. Province of Granada, Spain. Twenty healthy male adolescents aged 11-14 years, selected based on medical questionnaire, physical examination and nutritional survey of food habits and lifestyle. Mean Zn intake was 11·36 (se 0·31) mg/d, 76% of the recommended value for Spanish adolescents. Zn absorption (2·53 (se 0·55) mg/d) was close to the value of 3·0 mg/d required for the growth spurt. Zn status biomarkers and growth parameters were within the normal values for this age group. Although a diet based on Mediterranean patterns is associated with factors which can affect Zn absorption, such as high consumption of phytate, its consumption in adequate amounts allows Zn status to be maintained during adolescence. Due to the importance of Zn in preventing growth and behavioural disorders among adolescents, long-term intervention trials to investigate the suitability of the Mediterranean diet with respect to Zn requirements at this time of life are needed.

Biofortified foods are a new approach to increase minerals in the diet, and evidence suggests that zinc (Zn) biofortification can improve Zn physiological status in humans. This systematic review aimed to answer the question: "What are the effects of the consumption of Zn biofortified foods on Zn status in humans?". This review was conducted according to PRISMA guidelines and registered in PROSPERO (CRD42021250566). PubMed, Cochrane, Scopus and Science Direct databases were searched for studies that evaluated the effects of Zn biofortified foods on Zn absorption. Of 4282 articles identified, nine remained after inclusion/exclusion criteria were applied. Limitations in study quality, external and internal validity (bias/confounding), and study power were evaluated. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) was used to assess the certainty of evidence. Of the nine articles included, five observed an increase in total Zn absorption, and one showed that Zn participated in the conversion of linoleic acid to dihomo-γ-linolenic acid. By increasing the amount of Zn in the food, Zn biofortification can reduce the phytate:Zn molar ratio and improve Zn absorption in humans. More studies are needed to clarify what portion of Zn biofortified foods/day is needed to achieve a significant effect on Zn status.

Zn absorption was investigated in healthy elderly subjects aged 71-78 years and in young subjects aged 23-43 years using serum concentration curve (SCC) tests. Both groups had similar Zn and protein status. The increase in serum Zn was monitored for 180 min after ingestion of 200 ml of soya milk enriched with 50 mg of Zn. Three levels of phytic acid were used: 0 g/200 ml (totally dephytinized soya milk), 0.13 g/200 ml (half dephytinized), and 0.26 g/200 ml (natural phytic acid content). In a first study the effect of 0 v. 0.26 g/200 ml phytic acid was compared in 10 elderly and 10 young subjects, each subject receiving both treatments. In a second study soya milks with 0 and 0.13 g/200 ml were tested in nine elderly and ten young subjects, again receiving both treatments. Mean areas under the curve of the SCC tests conducted with the 0 g/200 ml soya milk were found to be the same in both studies. Phytic acid strongly depressed Zn absorption in both studies (P < or = 0.05), but to a greater extent at the 0.26 g/200 ml level. No difference was found between the groups of young and elderly subjects. Therefore, no significant effect of aging on Zn absorption, as evaluated by the SCC test, or on the inhibitory effect of phytic acid was detected.

Absorption, retention and excretion of 65Zn in rats from excisional wounds treated with 65Zn-labelled zinc tape were studied. The absorption of 65Zn was marked and indicates that the absorption of zinc from the tape is more than sufficient to account for the increases in zinc concentrations seen in several tissues. The distribution, retention and excretion of 65Zn from the zinc tape followed a pattern similar to that of 65Zn injected into non-operated and operated rats. This indicates that the zinc from the tape is present in the body not as zinc oxide, as it is in the adhesive substance of the tape, but as zinc in those forms which are originally found in the body and that zinc oxide is ionized before absorption. In tissues with a rapid uptake of zinc more than 50% of the total concentration of zinc derived from the zinc tape after eight days of treatment. In operated animals which were not treated with zinc tape a decline was seen in the serum zinc concentration and excretion of zinc with a concomitant increase in the liver concentration of zinc.

Effects of iron, tin, and copper on zinc absorption in humans

We investigated the effect of dietary phytase on the true absorption and endogenous fecal excretion of zinc (Zn) using (67)Zn in growing pigs given a corn-soybean meal based diet. Ten crossbred barrows were fed the control diet containing 90-mg/kg Zn, 2.3-g/kg phytate-phosphorus and 3.7-g/kg non-phytate-phosphorus or the phytase diet containing similar amounts of Zn and phytate-phosphorus, and 1.4-g/kg non-phytate-phosphorus with 750-PU/kg phytase for 12 h/day. On day 6, the pigs were given 200 g of the corresponding diet labeled by (67)Zn for 2 h. We measured feed intake, fecal Zn concentration and (67)Zn abundance for the determination of apparent absorption, true absorption and endogenous fecal excretion of Zn. Although the apparent absorption of Zn did not significantly differ between the dietary groups, the phytase group had significantly more (P < 0.05) true absorption of Zn than the control group. The endogenous fecal excretion of Zn tended to be more (P = 0.07) in the phytase group than in the control group. These results suggest that dietary phytase improves Zn bioavailability through increasing the true absorption of Zn in growing pigs, which results in stimulating the endogenous fecal excretion of Zn when dietary Zn satisfies its requirement.

Zinc Absorption and Its Relationship to Intestinal Metallothionein