Selenium, zinc help prevent CKD development

Higher blood concentrations of heavy metals appear to contribute to chronic kidney disease (CKD), while elevated levels of plasma selenium and serum zinc reduce CKD risk, according to a Singapore study.

This finding indicates the protective benefit of increased selenium and zinc in the body against CKD, as well as avoidance of heavy metal exposures.

“Increasing the blood concentrations of selenium and zinc as well as avoiding heavy metal exposures might help to prevent the development of CKD,” the researchers said. “The accumulation of selenium and zinc appears to alleviate the damage caused by heavy metals to the kidneys.”

The database of the US National Health and Nutrition Examination Survey (NHANES) was accessed to extract data for this study. Four cycles of NHANES were used: 2011‒2012, 2013‒2014, 2015‒2016, and 2017‒2018).

In univariate analysis, the higher quartiles of plasma lead and cadmium concentration significantly correlated with CKD as compared with the lowest quartile. Along with folate, lead and cadmium tended to increase the likelihood of CKD development. [Ann Acad Med Singap 2023;52:398-410]

Increased plasma selenium and serum zinc levels, on the other hand, were associated with a lower CKD risk. These findings persisted in multivariate analysis after adjusting for relevant confounders.

Notably, higher quartiles of plasma cadmium correlated with greater odds of CKD, while higher quartiles of plasma selenium and serum zinc were significantly associated with a reduced CKD risk.

“Industrial development, which intends to meet the demands of a growing and modern population, has contributed to extremely dangerous chemicals in the environment that broadly affect human health—including heavy metals,” the researchers said.

Heavy metal

Previous studies have reported the associations of heavy metals with reductions in glomerular filtration rate (GFR), providing significant data on renal function and heavy metals. One study found that excessive cadmium excretion was indicative of renal tubular damage. [Environ Int 2019;131:104993; Toxics 2020;8:86; Int J Environ Res Public Health 2022;19:6646]

“The likelihood of CKD is increased in individuals with elevated levels of toxic heavy metals in the blood but is decreased with elevated levels of plasma selenium and serum zinc,” the researchers said. “High serum zinc appears to interact with low-toxicity heavy metals to reduce the risk of developing CKD.”

Selenium is an antioxidant that is responsible for biological protection against oxidative damage. In an earlier study, this nutrient was found to alter estimated GFR in environment toxicant-induced CKD. It also helps reduce the toxicity of arsenic, lead, mercury, and cadmium. [Environ Res 2017;158:625-648; J Hazard Mater 2019;375:224-232; Physiol Res 2008;57:403-411]

Zinc, on the other hand, has several physiological functions, such as immune maturation, reproduction, and cell growth. This metal is also a significant component of copper and zinc superoxide dismutase, acts as defense mechanism for thiols and other chemical groups, and protects against free radical damage by maintaining sufficient metallothionein levels. [Comp Biochem Physiol C Toxicol Pharmacol 2007;146:443-459; Ecotoxicol Environ Saf 2019;168:146-163]

“Zinc has similar physical and chemical properties to cadmium and can compete for binding sites in metal-absorbing proteins and enzyme proteins,” the researchers said.