Zinc and copper retention during pregnancy: the adequacy of prenatal diets with and without dietary supplementation

Lower serum zinc level is associated with higher fasting insulin in type 2 diabetes mellitus (T2DM) and relates with disturbed glucagon suppression response in male patients

AIMS

Zinc ion can play critical role in glycemic control in diabetes mellitus (DM), contributing to both insulin synthesis and secretion. In this study, we aimed to investigate the level of zinc in diabetic patients and its association with glycemic parameters, insulin, and glucagon level.

METHODS

112 individuals (59 cases of type 2DM and 53 non-diabetic controls) were included in this study. Biochemical parameters (FBG, 2hpp, HbA1C), and zinc level in the serum were measured using colorimetric assays. Insulin and glucagon were measured by ELISA method. HOMA-IR, HOMA-B, reciprocal HOMA-B, and Quicki indices were calculated using appropriate formula. For further analysis, patients were divided into two groups: high (>135.5 μg/dl) and low (<135.5 μg/dl) zinc. Glucagon suppression was considered yes if 2hpp glucagon < fasting glucagon.

RESULTS

Our results showed that serum Zn level in type 2 DM patients was lower than control (P value=0.02). Patients with lower Zn had higher fasting insulin (P value=0.006) and higher β-cell activity index (HOMA-B, p value=0.02), however fasting glucagon and parameters of hyperglycemia (FBG, 2hpp, Hba1C) were not different. Moreover, insulin sensitivity and resistance indices (Quicki, HOMA-IR,1/HOMA-IR) showed non-significantly improved status in high Zn group. We found non-significant association between glucagon suppression and Zn level in both genders (N = 39, p value = 0.07), however, it was significant in males (N = 14, p value = 0.02).

CONCLUSION

Altogether, our results indicated reduced serum Zn in type 2DM can exacerbate hyperinsulinemia and glucagon suppression (only significant in the male), highlighting its importance in type 2DM control.

Is the Western diet adequate in copper?

Copper has been known to be essential for health for more than three quarters of a century. Myriad experiments with animals reveal that the cardiovascular, musculoskeletal and nervous systems are most sensitive to deficiency. Copper in the Western diet has been decreasing at least since the 1930s; half of the adult population consumes less than the amount recommended in the European Communities and the United Kingdom. At least one fourth of adults consume less than the estimated average requirement published for the United States and Canada. Hundreds of people have been reported in journals about medicine and neurology rather than nutrition to have impaired copper nutriture based on the criteria of low copper concentrations and low activities of enzymes dependent on copper in various fluids and tissues. In contrast, only 46 people have participated in depletion/repletion experiments needed to define requirements. Almost 1000 people have benefited from supplements containing copper in controlled trials. People deficient in copper are being identified increasingly; it is unknown if unusually high requirements or unusually low diets are causal. Alzheimer's disease, ischemic heart disease and osteoporosis are the most likely human illnesses from low copper intakes.

Nutrition in pregnancy: mineral and vitamin supplements

Pregnancy is associated with physiologic changes that result in increased plasma volume and red blood cells and decreased concentrations of circulating nutrient-binding proteins and micronutrients. In many developing countries, these physiologic changes can be aggravated by undernutrition, leading to micronutrient deficiency states, such as anemia, that can have disastrous consequences for both mothers and newborn infants. Multiple micronutrients are often taken by pregnant women in developed countries, but their benefits are limited, except for prophylactic folic acid taken during the periconceptional period. Women in developing countries may benefit from multiple-micronutrient prophylaxis in pregnancy, but the underlying basis and rationale for changing from supplementation with iron and folate to supplementation with multiple micronutrients has not been debated in the context of existing program objectives. There is an urgent need for this discussion so that both program effectiveness and program efficacy can be improved.

Maternal zinc and fetal neural tube defects

Among the factors implicated in the heterogeneous etiology of neural tube defects (NTDs) is the trace element zinc (Zn). In a case-control study, we collected midtrimester maternal toenail samples for multiple trace element analyses, including Zn, which were assayed by neutron activation analysis. We studied 17 women with NTD offspring and 1,787 controls. The crude OR for NTD comparing Zn values greater than normal range to normal Zn values was 3.2 (95% CI 1.1,9.7). These results were not materially affected when adjustment was made for folic acid supplementation. An overall increased risk for NTD associated with increasing toenail Zn was also evident. A matched subset of 17 cases and 73 controls yielded a crude OR of 3.1 (95% CI 0.9,10.3) when cases with elevated Zn (greater than or equal to 120 ppm) were compared to those with normal Zn. Matched analyses controlling for folic acid supplements, family history of NTD, assay batch, age of mother and year of delivery yielded an OR of 5.0 (95% CI 1.1,21.6). This study reveals an association between increased toenail Zn in the second trimester of pregnancy and the risk of having a child with an NTD. Whether Zn sequestration has resulted in relative Zn deficiency at the site of neural tube closure remains uncertain.

The role of zinc in reproduction. Hormonal mechanisms

Zinc is a very important element in the reproductive cycle of species. In humans, it is necessary for the formation and maturation of spermatozoa, for ovulation, and for fertilization. During pregnancy, zinc deficiency causes a number of anomalies: spontaneous abortion, pregnancy-related toxemia, extended pregnancy or prematurity, malformations, and retarded growth. Delivery is adversely affected by deficiency. These different effects of zinc can be explained by its multiple action on the metabolism of androgen hormones, estrogen and progesterone, together with the prostaglandins. Nuclear receptors for steroids are all zinc finger proteins. Zinc supplementation has already proven beneficial in male sterility and in reducing complications during pregnancy. However, it would be worth conducting larger-scale trials to confirm these beneficial effects.

Effects of a multivitamin mineral supplement on zinc and copper status during pregnancy

The effect of a multivitamin-mineral supplement was investigated during pregnancy according to a double-blind protocol by determining zinc and copper in maternal plasma, mononuclear and polynuclear zinc and copper at the third, sixth, eighth, and ninth months of gestation. The subjects were supplemented from the first trimester until delivery. A significant decrease was observed in plasma zinc that varied from 11.5 mumol/L to 10.8 mumol/L in the supplemented group (n = 29) and from 11 mumol/L to 10 mumol/L in the placebo group (n = 33) at 3 and 9 mo of gestation, respectively. In contrast, plasma copper levels increased in a way depending upon the stage of gestation in both groups: from 24.7 to 28.2 mumol/L in the treated group and from 24.9 to 30.9 mumol/L in the placebo group at 3 and 9 mo of gestation, respectively, but the difference was only significant in the placebo group. No difference between groups was observed in mononuclear and polynuclear zinc or copper levels. These trace elements were also determined in cord blood at delivery. There were no statistically significant differences in zinc and copper concentration found in placebo group and supplemented group. Finally, the beneficial effect of supplementation on muscular cramps and appearance of vergetures was noted.