MHD acts as the mainstay of treatment for those suffering from end-stage kidney disease and who are either waiting for a renal transplantation, or simply deemed unsuitable for transplantation.
At the same time, zinc is considered an essential trace element for humans, and zinc deficiency has been linked to adverse outcomes in kidney disease.
Based on this, researchers at the Guangzhou University of Chinese Medicine Southern Medical University conducted systematic review and meta-analysis of RCTs of zinc supplementation's effects on lipid profile and nutritional status, as well as its anti-inflammatory and antioxidant activity in MHD patients.
They subsequently observed that zinc supplementation tended to lead to higher levels of serum zinc and superoxide dismutase, greater dietary protein intake, and lower levels of C-reactive protein and malondialdehyde.
When it came to lipid profile, however, zinc supplementation did not seem to have a significant effect.
The researchers further wrote that in their meta-regression analysis, they "found that serum zinc levels correlated positively with intervention time and varied greatly by ethnicity".
They added that the results from the Beff and Egger tests showed "no significant bias" in their meta-analysis, and that the results of the subgroup analysis supported these outcomes.
They listed several possible limitations of the review, including the lack of analysis of zinc supplementation's adverse outcomes, i.e., the harmfulness of excessive zinc intake, which can suppress iron and copper absorption and possibly cause nerve damage.
They added that among the studies reviewed, only one had followed up with patients about whether or not they had experienced any adverse effects.
At the same time, different geographical regions produced varying epidemiology: zinc deficiency was prevalent in East Asia (with almost 40% to 60% of the population having mild to moderate zinc deficiency), but uncommon in Europe and the US.
However, a lack of data in most outcomes meant that the researchers could not analyse racial sub-groups, leading to possible selection bias in the results.
They concluded: "Our meta-analysis suggests that zinc supplementation benefits the nutritional status of MHD patients and shows a time-effect relationship. It also leads to an anti-inflammatory and anti-oxidative effect in MHD patients.
"Still, there is a need for more evidence regarding the effects on lipid profile. Given the presence of data deficiency in this study, further studies are warranted to comprehensively investigate the effects of zinc supplementation on clinical endpoint events and on race."
"Effect of Zinc Supplementation on Maintenance Hemodialysis Patients: A Systematic Review and Meta-Analysis of 15 Randomized Controlled Trials"
Authors: Ling-Jun Wang, et al.