Serum zinc in highly trained adolescent gymnasts

Influence of physical training on intracellular and extracellular zinc concentrations

Background

Physical exercise affects zinc (Zn) homeostasis. This study aimed to analyze the influence of physical training on extracellular (serum, plasma, and urine) and intracellular (erythrocytes and platelets) concentrations of Zn.

Methods

Forty young men, divided into a training group (TG; n = 20; 18.15 ± 0.27 years; 68.59 ± 4.18 kg; 1.76 ± 0.04 m) and a control group (CG; n = 20; 19.25 ± 0.39 years; 73.45 ± 9.04 kg; 1.79 ± 0.06 m), participated in this study. The TG was formed by semiprofessional soccer players from a youth category with a regular training plan of 10 h/week. The CG was formed by healthy men who did not practice physical exercise and had not followed any specific training plan. Plasma, serum, urine, erythrocyte, and platelet samples of Zn were obtained and analyzed by inductively coupled plasma mass spectrometry.

Results

The TG showed elevated plasma Zn concentrations (p < 0.01) despite similar intakes. However, TG showed reduced absolute (p < 0.01) and relative (p < 0.05) Zn concentrations in erythrocytes.

Conclusions

Athletes who underwent regular physical training showed elevated plasma and reduced erythrocyte Zn concentrations despite similar intakes to the CG.

Iron and zinc homeostases in female rats with physically active and sedentary lifestyles

To determine the effects of repeated physical activity on iron and zinc homeostases in a living system, we quantified blood and tissue levels of these two metals in sedentary and physically active Long-Evans rats. At post-natal day (PND) 22, female rats were assigned to either a sedentary or an active treatment group (n = 10/group). The physically active rats increased their use of a commercially-constructed stainless steel wire wheel so that, by the end of the study (PND 101), they were running an average of 512.8 ± 31.9 (mean ± standard error) min/night. After euthanization, plasma and aliquots of liver, lung, heart, and gastrocnemius muscle were obtained. Following digestion, non-heme iron and zinc concentrations in plasma and tissues were measured using inductively coupled plasma optical emission spectroscopy. Concentrations of both non-heme iron and zinc in plasma and liver were significantly decreased among the physically active rats relative to the sedentary animals. In the lung, both metals were increased in concentration among the physically active animals but the change in zinc did not reach significance. Similarly, tissue non-heme iron and zinc levels were both increased in heart and muscle from the physically active group. It is concluded that repeated physical activity in an animal model can be associated with a translocation of both iron and zinc from sites of storage (e.g. liver) to tissues with increased metabolism (e.g. the lung, heart, and skeletal muscle).

Fluoride Alters Serum Elemental (Calcium, Magnesium, Copper, and Zinc) Homeostasis Along with Erythrocyte Carbonic Anhydrase Activity in Fluorosis Endemic Villages and Restores on Supply of Safe Drinking Water in School-Going Children of Nalgonda District, India

The present study aimed to determine the serum trace elements (copper (Cu), zinc (Zn), calcium (Ca), magnesium (Mg)) along with erythrocyte carbonic anhydrase (CA) activity and effect of intervention with safe drinking water for 5 years in the school children of fluorosis endemic area. For this purpose, three categories of villages were selected based on drinking water fluoride (F): Category I (control, F = 1.68 mg/L), category II (affected F = 3.77 mg/L), and category III (intervention village) where initial drinking water F was 4.51 mg/L, and since the last 5 years, they were drinking water containing < 1.0 mg/L F. The results revealed that urinary F was significantly (P < 0.05) higher in category II compared to categories I and III. A significant (P < 0.05) increase in serum Cu and Mg was observed in category II compared to category I. Serum Zn and Ca was significantly (P < 0.05) decreased in categories II and III compared to category I. The erythrocyte CA activity was decreased in the category II compared to category I. However, in the category III, erythrocyte CA activity was comparable to the control group. In conclusion, F exposure altered elemental homeostasis which has restored to some extent on intervention by safe drinking water for 5 years in school-going children.

Zinc deficiency and its predictive capacity for anemia: Unique model in school children

BACKGROUND

Zinc deficiency is thought to be common in children, but its predictive capacity for anemia is unclear. Thus, this study identified zinc deficiency in school children, and investigated the association between zinc status and hemoglobin, together with other estimates of anemia.

METHODS

For this case-control study, 349 of 483 children between 6.5 and 14.8 years old were included from primary schools in Bolu, Turkey. We measured weight, length, body mass index, and complete blood count with serum zinc, ferritin, vitamin B12 and folate. We investigated the differences between the groups and the effects of independent predictors such as age, gender, ferritin, zinc, vitamin B12 and folate on hemoglobin, on hierarchical multiple regression analysis.

RESULTS

Thirty-eight (10.9%) of 349 children had low serum zinc concentration, and 21 (6.0%) were anemic. There were 12 anemic children in the zinc-deficient group and nine in the zinc-sufficient control group (31.5% vs 2.9%) with similar ferritin levels. On regression analysis, zinc had the strongest association with hemoglobin. On receiver operating characteristic analysis, the cut-off for serum zinc for prediction of anemia was 71.5 μg/dL.

CONCLUSIONS

The strongest association of zinc with hemoglobin suggests that low zinc contributed the most to the observed anemia in children.

Nutritional deficiencies during normal growth

Nutritional deficiencies have always been a major consideration in pediatrics. Although the classic forms of many of the well-documented nutritional deficiencies are memorized during training as a physician, nutritional deficiencies that can occur in otherwise asymptomatic normally growing children are often overlooked. The two most common deficiencies seen in children who are growing normally are iron and vitamin D deficiencies. These deficiencies are surprisingly common and can have a significant impact on the overall health of a child. This article reviews these nutritional deficiencies and other less commonly seen deficiencies in children who are otherwise growing normally.

Low dietary zinc decreases erythrocyte carbonic anhydrase activities and impairs cardiorespiratory function in men during exercise

BACKGROUND

The role of zinc in promoting physiologic function during exercise is not well understood. Although some zinc-containing enzymes are postulated to regulate energy expenditure, data are limited on the effect of restricted dietary zinc on metabolic responses during exercise.

OBJECTIVE

This study determined the effects of low zinc intake on carbonic anhydrase activity in red blood cells (RBCs) and cardiorespiratory function during exercise.

DESIGN

In this double-blind, randomized crossover study, 14 men aged 20-31 y were fed low-zinc and supplemented (3.8 and 18.7 mg/d) diets made up of Western foods for 9-wk periods with a 6-wk washout. Peak work capacity, determined by using a cycle ergometer and a graded, progressive protocol, and a prolonged submaximal test (70% peak intensity for 45 min) were administered during the second and ninth weeks of each diet period.

RESULTS

Dietary zinc did not affect hemoglobin or hematocrit. Low dietary zinc resulted in lower (P < 0.05) serum and erythrocyte zinc concentrations, zinc retention, and total carbonic anhydrase and isoform activities in RBCs. Peak oxygen uptake, carbon dioxide output, and respiratory exchange ratio were lower (P < 0.05), and ventilatory equivalents for metabolic responses during exercise were greater (P < 0.05), with low than with supplemental zinc intake. Similar functional responses were observed during prolonged, submaximal exercise.

CONCLUSION

These findings indicate that low dietary zinc is associated with significant reductions in zinc status, including RBC carbonic anhydrase activities, and impaired metabolic responses during exercise.

The effects of intensive training on insulin-like growth factor I (IGF-I) and IGF binding proteins 1 and 3 in competitive cyclists: relationships with glucose disposal

The aim of the present study was to determine whether 4 months of intensified training would result in modified plasma insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 1 (IGFBP-1) or IGFBP-3 in eight competitive cyclists and eight sedentary individuals and to define the relationships of these factors with glucose disposal. Insulin sensitivity and glucose effectiveness--that is, the fractional disappearance of glucose independent of any change in insulinaemia--were measured with the minimal model (mathematical analysis of frequently sampled intravenous glucose tolerance test). Both glucose effectiveness and insulin sensitivity were higher in the cyclists than in the sedentary individuals, but did not increase further with training. IGF-I was higher in the cyclists than in the sedentary group only after raining (P < 0.05). Plasma IGFBP-1 and IGFBP-3 increased after training (38 and 20%, respectively; P < 0.05) in the cyclists and were higher than in the sedentary individuals (P < 0.05). IGF-I was negatively correlated with insulin sensitivity before and after training (r = -0.66 and -0.67, respectively; P < 0.05) and IGFBP-1 was negatively correlated with glucose effectiveness before andafter training (r = -0.68 and -0.77, respectively; P < 0.05). Our results show that strenuous endurance training improves the somatotrope axis (growth hormone-IGF) and that IGFBP-1 may be involved in glucose homeostasis, possibly by limiting the exercise-induced increase in glucose disposal, in competitive cyclists.

Effect of training on the GH/IGF-I axis during exercise in middle-aged men: relationship to glucose homeostasis

The aim of this study was to compare circulating levels of growth hormone (GH), IGF-I, and IGF-binding protein (IGFBP)-1 and IGFBP-3 in response to a long-duration endurance exercise in trained vs. sedentary middle-aged males and to determine whether a relationship with glucose homeostasis exists. Seven trained men (Tr) were compared with seven age-matched sedentary men (Sed) during two trials of 60 min of cycling exercise performed below (-VT) and above (+VT) the ventilatory threshold. Insulin sensitivity (S(I)) was higher in Tr than in Sed (P < 0.001). Basal GH, IGF-I, and IGFBP-1 and -3 were higher in Tr (P < 0.05). During +VT, Tr had a threefold higher GH response, whereas their blood glucose level was better maintained (P < 0.05). Basal IGFBP-1 was correlated with S(I) (P < 0.01). These data indicate that endurance training in middle-aged men increased the activity of the GH/IGF-I system and improved glucoregulation both at rest and during high-intensity endurance exercise.

Magnesium, zinc, and chromium nutrition and athletic performance

Magnesium, zinc and chromium are mineral elements required in modest amounts for health and optimal performance. Accumulating evidence supports the hypothesis that magnesium and zinc play significant roles in promoting strength and cardiorespiratory function in healthy persons and athletes. Differences in study designs, however, limit conclusions about recommendations for intakes of magnesium and zinc needed for optimal performance and function. The role of chromium in supporting performance is not well established. There is a compelling need to confirm and extend findings of beneficial effects of magnesium and zinc function and performance of humans. Suggestions for an experimental model and specific topics for research to advance knowledge of mineral nutrition to promote attainment of genetic potential for optimal performance are provided.