Zinc nutritional status in obese children and adolescents

Studies in animals and humans have corroborated that zinc (Zn) metabolism is altered in obesity. The present work intends to evaluate the Zn nutritional status in obese children and adolescents by the determination of some biochemical parameters and analyses of the diets. The investigation was carried out in a group of obese children and adolescents (n=23) and compared to a control group (n=21), both between 7 and 14 yr of age. A software analyzed diet information from 3-d food records. Body composition was evaluated by body mass index, bioelectrical impedance, and skinfold measurements. Zinc nutritional status was evaluated by Zn determination in plasma, erythrocyte, and 24-h urine, by atomic absorption spectrophotometry (γ=213.9 nm). Diets consumed by both groups had marginal concentrations of zinc. Zinc concentrations in plasma and erythrocytes were significantly lower in the obese group. Urinary zinc excretion was significantly higher in the same group. The results allowed one to conclude that zinc nutritional status in obese individuals is altered.     

Nutritional Status of Zinc in Children with Down Syndrome

Experimental and clinical studies have established that zinc metabolism is altered in individuals with Down syndrome (DS). The present study intends to evaluate the nutritional status of zinc in children with DS by determining their biochemical and dietary parameters. The investigation was carried out on a group of children with DS (n = 35) and compared with a control group (n = 33), both aging between 4 and 11 years. Weight-for-age, height-for-age, and weight-for-height indexes and diet were evaluated by using a 3-day dietary record. Zinc was evaluated in plasma, erythrocytes, and 24-h urine collection by using the method of atomic absorption spectroscopy. The frequency of short stature was higher in children with DS. Both groups presented high protein content, adequate concentrations of lipids and carbohydrates, and deficit in calories. Adequate zinc intake was observed in 40% of children with DS and in 67% of the control group. Zinc concentrations were significantly lower in plasma and urine and higher in erythrocytes of children with DS. The results allowed us to conclude that the altered zinc nutritional status of individuals with Down syndrome contributes to clinical disturbances that usually appear with aging in these patients.     

Effects of zinc supplementation in patients with type 1 diabetes

The purpose of this study was to identify the effect of oral zinc supplementation in patients with type 1 diabetes (T1DM) on metabolic control and zinc blood concentrations. The sample consisted of 20 patients with T1DM and a control group (n=17). Metabolic control was evaluated by glycemia at fast, 24 h glycosuria, and HbA1c. Zinc concentrations were measured in plasma and erythrocytes. After the first collection of biological material, oral zinc supplementation was initiated and continued for 4 mo in T1MD patients (T1). Daily dosages were established based on Dietary Recommended Intakes (DRIs), considering zinc intake based on data from other studies previously performed with this population. All analyses were repeated after supplementation (T2). Metabolic control was unsatisfactory, with an HbA1c increase at T2. There was no difference in zinc concentrations in plasma and erythrocytes between patients with T1DM and control. Zinc concentrations in plasma were within the normal range in T1MD before and after supplementation and the control. Zinc concentrations in erythrocyte presented lower than normal values for all groups. A zinc increase in erythrocyte after supplementation was observed in T1DM patients, although without statistical significance. More studies are needed to confirm oral zinc supplementation as nutritional management in diabetes.     

Zinc Nutritional Status in Adolescents with Down Syndrome

Studies have evidenced that zinc metabolism is altered in presence of Down syndrome, and zinc seems to have a relationship with the metabolic alterations usually present in this syndrome. In this work, the Zn-related nutritional status of adolescents with Down syndrome was evaluated by means of biochemical parameters and diet. A case–control study was performed in a group of adolescents with Down syndrome (n = 30) and a control group (n = 32), of both sexes, aged 10 to 19 years. Diet evaluation was accomplished by using a 3-day dietary record, and the analysis was performed by the NutWin program, version 1.5. Antropometric measurements were performed for evaluation of body composition. The Zn-related nutritional status of the groups was evaluated by means of zinc concentration determinations in plasma and erythrocytes, and 24-h urinary zinc excretion, by using the method of atomic absorption spectroscopy. The diet of both groups presented adequate concentrations of lipids, proteins, carbohydrates, and zinc. The mean values found for zinc concentration in erythrocytes were 49.2 ± 8.5 μg Zn/g Hb for the Down syndrome group and 35.9 ± 6.1 μg Zn/g Hb for the control group (p = 0.001). The average values found for zinc concentration in plasma were 67.6 ± 25.6 μg/dL for the Down syndrome group and 68.9 ± 22.3 μg/dL for the control group. The mean values found for zinc concentration in urine were 244.3 ± 194.9 μg Zn/24 h for the Down syndrome group and 200.3 ± 236.4 μg Zn/24 h for the control group. Assessment of body composition revealed overweight (26.7%) and obesity (6.6%) in the Down syndrome group. In this study, patients with Down syndrome presented altered zinc levels for some cellular compartments, and the average zinc concentrations were low in plasma and urine and elevated in erythrocytes.     

Zinc status in plasma of obese individuals during glucose administration

To know whether plasma zinc status is altered under acute hyperglycemic state, the interrelationships among plasma glucose, insulin, and zinc concentrations during oral glucose tolerance test (OGTT) in obese individuals and their lean controls were studied. Plasma glucose and insulin concentrations under fasting as well as those values in response to OGTT were significantly higher in obese individuals than those in lean controls. On the other hand, the obese had lower fasting plasma zinc concentrations compared to lean controls (13.5 vs 18.1 Μmol/L,p < 0.005). Under fasting, plasma zinc concentrations in overall individuals inversely correlated to their body mass index (BMI) (r = -0.516), plasma glucose (r = -0.620), and plasma insulin (r = -0.510). However, there were no significant changes in plasma zinc and copper values during OGTT in both obese individuals and lean controls. This study showed that plasma zinc values had no changes during OGTT in obese individuals. The results also indicated that lower fasting plasma zinc concentrations in obese individuals were not the short-term metabolic result.     

Distinctive modulation of inflammatory and metabolic parameters in relation to zinc nutritional status in adult overweight/obese subjects

Overweight and obesity are associated with low grade of inflammation and chronic inflammatory response characterized by abnormal production and activation of some pro-inflammatory signalling pathways. Taking into account that obesity is the direct result of an imbalance between energy intake and energy expenditure, the nutritional factors in the diet, with particular focus on zinc, may play a pivotal role in the development of obesity-associated comorbidities. Considering the potential interactions among zinc nutritional status, inflammation, overweight/obesity and insulin secretion, the aim of the present work was to clarify the influence of zinc dietary intake on some metabolic, inflammatory and zinc status parameters in adult overweight/obese subjects. We found a close interrelationship between nutritional zinc and obesity. In particular, subjects with a lower zinc dietary intake display a deeper inflammatory status, general impairment of the zinc status, an altered lipid profile and increased insulin production with respect to obese subjects with normal zinc dietary intake. Moreover, in the presence of low dietary zinc intake, the obese subjects are less capable to respond to oxidative stress and to inflammation leading to the development of obesity or to a worsening of already preexisting obesity status. In conclusion, a possible zinc supplementation in obese subjects with a deeper inflammatory status and more altered zinc profile may be suggested in order to limit or reduce the inflammation, taking also into account that zinc supplementation normalizes “inflammaging” as well as zinc profile leading to a correct intra- and extracellular zinc homeostasis.     

Effects of zinc supplementation on the plasma glucose level and insulin activity in genetically obese (ob/ob) mice

The effects of zinc supplementation (20 mM ZnCl₂ from the drinking water for eight weeks) on plasma glucose and insulin levels, as well as its in vitro effect on lipogenesis and lipolysis in adipocytes were studied in genetically obese (ob/ob) mice and their lean controls (+/?). Zinc supplementation reduced the fasting plasma glucose levels in both obese and lean mice by 21 and 25%, respectively (p < 0.05). Fasting plasma insulin levels were significantly decreased by 42% in obese mice after zinc treatment. In obese mice, zinc supplementation also attenuated the glycemic response by 34% after the glucose load. The insulin-like effect of zinc on lipogenesis in adipocytes was significantly increased by 80% in lean mice. However, the increment of 74% on lipogenesis in obese mice was observed only when the zinc plus insulin treatment was given. This study reveals that zinc supplementation alleviated the hyperglycemia of ob/ob mice, which may be related to its effect on the enhancement of insulin activity.     

Plasma Zinc,Copper, and Serum Thyroid Hormones and Insulin Levels After Zinc Supplementation Followed by Placebo in Competitive Athletes

Intense physical activity is associated with biological adaptations involving hormones and trace elements. Zinc supplementation may affect plasma copper concentration, thyroid-stimulating hormone (TSH), thyroid hormones, insulin, and glucose homeostasis, but data in athletes are scarce. The aim of this study was to evaluate in competitive athletes (cyclists, n = 7, 32 ± 8 years) the effect of zinc supplementation (22 mg/day as zinc gluconate) during 30 days, and discontinuation using placebo (maltodextrin) during the following 30 days, on plasma zinc and copper concentrations, serum thyroid hormones, insulin and glucose levels, and HOMA2-IR. Compared to baseline, plasma zinc and Zn:Cu plasma ratio increased, but plasma copper decreased after zinc supplementation (day 30) and discontinuation (day 60) (p < 0.05). Zn supplementation and discontinuation had no effect on TSH, T3, and T4. Fasting serum insulin and HOMA2-IR increased (27% and 47%, respectively) on day 60 compared to baseline (p = 0.03), suggesting a delayed effect of zinc supplementation. Moreover, plasma zinc was positively associated with serum insulin (r = 0.87, p = 0.009) and HOMA2-IR (r = 0.81, p = 0.03) after zinc supplementation (day 30), indicating that supplemental zinc may impair glucose utilization in cyclists.     

Effect of zinc supplementation on the antioxidant,copper, and iron status of physically active adolescents

Puberty associated with intense physical activity results in oxidation stress. Zinc supplementation may benefit antioxidant capacity although it may also affect iron and copper status. This study evaluated the effect of zinc supplementation on antioxidant, zinc and copper status of physically active male football players (13 years ± 0.4 years), divided in two groups and studied during 12 weeks: Zn‐supplemented (Zn‐SUP, 22 mg Zn d^?1 as zinc gluconate, n = 21) and placebo (PLA, n = 26). At baseline, there was no significant difference in biochemical indices between the two groups. After treatment, plasma zinc and erythrocyte iron increased in both groups (p < 0.001); urinary zinc increased (p < 0.001) only in Zn‐SUP, and erythrocyte zinc decreased (p = 0.002) only in PLA. Plasma iron and copper decreased (p = 0.01 and p = 0.015, respectively) only in Zn‐SUP. Plasma ferric‐reducing ability and plasma conjugated dienes increased, and erythrocyte osmotic fragility decrease in both groups, although the latter two were significantly lower in Zn‐SUP compared to PLA (p < 0.01). In conclusion, our study indicates that the use of 22 mg d^?1 of supplemental zinc during 12 week in adolescent athletes did not affect growth, improved markers of antioxidant status but reduced plasma iron and copper. Therefore, it appears that the use of zinc supplementation by healthy adolescent athletes benefits their antioxidant capacity but impairs copper and iron nutritional status. Copyright © 2009 John Wiley & Sons, Ltd.     

Dietary Intervention Causes Redistribution of Zinc in Obese Adolescents

Obese people tend to have low zinc circulation levels; this is not always related to zinc intake but can reflect the distribution of zinc in relation to the proportion of body fat and factors related to the inflammatory processes that cause obesity. The purpose of this study was to assess zinc distribution in 15 obese adolescent girls before and after a nutritional orientation program. Participants ranged from 14 to 18 years old (postpubescent) and had a body fat percent (BF%) of >35 %. Zinc nutritional status and other zinc-dependent parameters, such as superoxide dismutase (SOD) and insulin levels, were assessed by biochemical analysis of plasma and erythrocytes, salivary sediment, and urine. Samples were collected before and after 4 months of dietary intervention. Dual energy X-ray absorptiometry (DXA) was used to verify BF% both at the beginning and at the end of the study. Food consumption was assessed in ten individual food questionnaires throughout the study; food groups were separated on the questionnaires in the same way as suggested by some authors to develop the Healthy Eating Index (HEI) but with the addition of zinc. After 4 months of nutritional orientation, 78 % of the participants showed a decrease in BF%. Intraerythrocytic zinc increased over the study period, while salivary sediment zinc, SOD, insulin, and Zn urinary24 h/creatinine all decreased (p?<?0.05). There was no difference in zinc intake throughout the study but participants did increase their consumption of fruits, dairy, and meats during the study (p?<?0.05). There were inverse and statistically significant correlations between the increased levels of intraerythrocytic zinc and decreased levels of SOD. There was also a statistically significant correlation between BF% and Zn urinary 24h/creatinine, and SOD. All these parameters were diminished at the end of the study. The dietary intervention for obese adolescent girls is effective with decrease of BF that led to the redistribution of zinc in the body as shown by the changes in erythrocytes, plasma, salivary, urine zinc, as well as the complementary parameters of insulin and SOD. These changes were not affected by zinc intake.