Comparisons of the effects of calcium carbonate and calcium acetate on zinc tolerance test in hemodialysis patients

Water-soluble vitamins and trace elements in children with chronic kidney disease stage 5d

Children receiving maintenance dialysis (chronic kidney disease (CKD) stage 5d) have unique risk factors for micronutrient deficiency or toxicity. Children receiving chronic dialysis often require specialized diet plans that may provide more than the recommended daily allowance (RDA) of water-soluble vitamins and micronutrients, with or without the addition of a kidney-friendly vitamin. The following is a comprehensive review of current literature on disorders of micronutrients in this population including those of water-soluble vitamins (vitamin C and vitamin B complexes) and trace elements (copper, selenium, and zinc) and has three areas of focus: (1) the risk factors and clinical presentations of disorders of micronutrients, both deficiency and toxicity, (2) the tools to evaluate micronutrient status, and (3) the central role of renal dietitians in optimizing nutritional status from a micronutrient perspective.

Effect of phosphate binders upon TSH and l-thyroxine dose in patients on thyroid replacement

BACKGROUND

While calcium carbonate is known to interfere with the gastrointestinal absorption of levothyroxine, we hypothesized that other phosphate binders would also bind to levothyroxine and decrease bioavailability of levothyroxine in dialysis patients.

METHODS

The records of 1,566 patients on hemodialysis who were being treated by the Hypertension, Nephrology, Dialysis, and Transplantation Center (the regional renal referral center for Eastern Alabama, USA) were evaluated. The type of phosphate binder and amount were then correlated (two-tailed Pearson Correlation) to TSH levels, serum phosphorus and the amount of levothyroxine taken. Friedman Test and Wilcoxon Signed Ranks Test were performed to analyze the significance of difference in thyroxine dosing and TSH levels between the different phosphate binders.

RESULTS

Sixty-seven patients were identified who were taking levothyroxine while taking three different kinds of phosphate binders; namely, calcium carbonate, calcium acetate, and sevelamer HCl. We found that the TSH levels of patients on calcium carbonate (P = 0.002) and sevelamer HCl (P = 0.033) were significantly higher than patients on calcium acetate with the difference increasing with time on each binder. Sevelamer was also found to be associated with significantly higher dosing requirement of thyroid replacement than those on either calcium carbonate or calcium acetate (Z = -3.17, P = 0.001).

CONCLUSION

Sevelamer (but not calcium acetate) in addition to calcium carbonate appears to interfere with the bioavailability of levothyroxine.

Zinc supplementation at conventional doses does not improve the disturbance of taste perception in hemodialysis patients

OBJECTIVE

To determine the effect of zinc supplementation on taste perception in a group of hemodialysis patients.

DESIGN AND SETTING

Double-blind randomized placebo-controlled study in a teaching hospital dialysis unit.

PATIENTS

Fifteen stable hemodialysis patients randomized to placebo (6 male, 2 female; median age, 67; range, 30 to 72 years) or treatment (5 male, 2 female; median age, 60; range, 31 to 76 years).

INTERVENTION

Treatment group received zinc sulfate 220 mg per day for 6 weeks, and the placebo group received an apparently identical dummy pill.

MAIN OUTCOME MEASURES

Taste scores by visual analogue scales, normalized protein catabolic rate and plasma, whole blood and red cell zinc levels.

RESULTS

At baseline, sweet and salt tastes were identified correctly by both groups. Sour was often confused with salt. Sour solutions of different concentrations were not distinguishable. Taste scores were not different after 6 weeks for either group. There was no significant increment in zinc levels or normalized protein catabolic rate for either group.

CONCLUSION

We found a disturbance of taste perception in hemodialysis patients, particularly for the sour modality, which was not corrected by this regimen of zinc supplementation. These results cast doubts on the conclusions of earlier studies that indicated an improvement in taste after zinc supplementation.

Plasma changes in micronutrients following a multivitamin and mineral supplement in healthy adults

OBJECTIVE

To estimate the micronutrient (riboflavin, folate, vitamin C, vitamin B(12), iron, zinc and copper) bioavailability in healthy adults from a multi-micronutrient dietary supplement to assess the possible influence on it by the tablet disintegration properties and by the relative intestinal permeability of subject.

METHODS

The bioavailability of seven micronutrients from a single brand of multi-micronutrient dietary supplement was measured on two separate occasions in the presence of a standardized test meal in 15 healthy adult subjects. Each subject visited the Metabolic Research Unit on four separate randomized occasions for an absorption test. One test measured the intestinal permeability. The other three tests measured the postprandial changes in plasma or serum concentrations after consuming a test meal alone (control:placebo effect), or the test meal with either whole or crushed and powdered dietary supplements. 15 healthy Caucasian adult volunteers, aged 42 +/- 14 years.

RESULTS

The 12 hour-post-dose AUC for riboflavin, folate and vitamin C (whole and crushed tablet), and that for vitamin B(12) (only for the crushed tablet treatment) and iron (only for the whole tablet treatment) were all significantly (p < 0.001) higher than after a test meal alone. In contrast there was no significant increase in the AUC after supplement intake for zinc and copper. Neither the form of the supplement for all micronutrients tested nor intestinal permeability of the subject for riboflavin, folate, vitamin C, iron, zinc and copper influenced the postdose nutrient AUC. In contrast, for vitamin B(12) the intestinal permeability of the subject influenced significantly the nutrient AUC (p = 0.003).

CONCLUSION

Tablet disintegration characteristics of this dietary supplement did not limit absorption of these seven micronutrients. The intestinal permeability of subject was only positively correlated with the B(12) bioavailability. Results are suggestive of using multi-micronutrients dietary supplements as a vehicle to decrease the prevalence of multiple micronutrient deficiencies overall for vitamins in healthy adults.

Short- and long-term uses of calcium acetate do not change hair and serum zinc concentrations in hemodialysis patients

Calcium acetate (CaAc) acutely decreases absorption of concomitantly administered zinc gluconate (Hwang et al., AJKD 1992), but its long-term effect on zinc metabolism has not been studied. This study is intended to elucidate whether use of CaAc as phosphate binder on a daily basis affects zinc status in hemodialysis (HD) patients. Effects of CaAc on serum zinc were studied in 44 HD patients for 8 weeks (short-term). In 10 of these patients, the changes of serum and hair zinc were followed for 8 months (long-term). The daily dose of CaAc contained 25.35 mmol elemental calcium. Serum and hair zinc concentrations were measured by atomic absorptiometry. Our results were as follows: (i) in the short-term study, serum zinc concentrations did not show a significant difference compared to the baseline; (ii) in the long-term study, serum zinc concentrations showed no significant difference between different time points (11.0+/-0.5 in the beginning, 11.9+/-0.4 after 2 months, 11.4+/-0.4 after 4 months and 11.3+/-0.5 micromol/L after 8 months, n=10). However, these values were all significantly lower than in the normal controls (15.7+/-0.5 micromol/L, n=16); (iii) hair zinc content was not significantly different from the baseline level (2.7+/-0.1 in the beginning, 2.4+/-0.1 after 2 months, 2.6+/-0.2 after 4 months, 3.1+/-0.1 micromol/g hair, and from that of normal controls, 2.7+/-0.2 micromol/g hair). In conclusion, daily application of CaAc does not significantly interfere with zinc absorption and storage in HD patients. However, the comparable hair zinc content in the presence of decreased serum zinc concentrations indicates that the metabolic processing of zinc in HD patients is different from that of normal individuals.