Selenium Counteracts Accelerated Aging from Toxic Heavy Metal Exposure, Suggests New Study

Highlights

• Approximately 49.3% of the US population is exposed to toxic heavy metals, such as cadmium, through environmental and dietary sources, which can lead to elevated blood levels of cadmium associated with accelerated aging.
• Higher blood levels of the mineral selenium were associated with mitigating accelerated aging from cadmium exposure.
• Associations uncovered in the study suggest that elevated blood cadmium confers age-accelerating effects through inflammation and that selenium reduces inflammation.

Published in Ecotoxicology and Environmental Safety, Huang and colleagues from Nanjing University in China unveil data associating elevated blood levels of the toxic heavy metal cadmium with accelerated biological aging (an assessment of how old your body’s cells and tissues are). Interestingly, elevated blood levels of a mineral essential for human physiological function, selenium, were associated with a protective effect against accelerated biological aging. These associations suggest that exposure to cadmium, through diet and other environmental factors, can accelerate aging and that increasing selenium intake, such as through supplementation, can counteract this effect.

Research suggests that a significant portion of the US population undergoes exposure to toxic levels of cadmium through dietary sources, industrial processes, and cigarette smoke. Accordingly, among US adults, an estimated 7.88% of men and 18.73% of women are exposed to cadmium levels associated with toxic effects on the kidneys. There is a significant correlation between cadmium exposure—which facilitates elevated inflammation, damage to the cell’s powerhouse (mitochondria), and DNA damage—and health phenomena related to aging. However, no study to date, before Huang and colleagues’ study, had attempted to find a correlation between cadmium exposure and accelerated aging.

Statistical Associations Suggest Selenium Counteracts Accelerated Aging from Elevated Levels of Cadmium

To measure how blood levels of cadmium and selenium influence biological age, Huang and colleagues used two separate biological age assessments—the Klemera-Doubal method (KDM-BA) and PhenoAge. The KDM-BA biological age assessment factors in parameters like blood chemistry and organ function to measure biological age. Moreover, PhenoAge uses nine blood markers, including white blood cell count and blood glucose levels, to measure biological age.

For the application of these two methods to analyze biological age, the China-based researchers assessed 7,119 adults with the KDM-BA method and 7,433 adults with the PhenoAge method, both groups having participants with an average age of 51 years. Analyzing the blood cadmium and selenium levels of the participants unraveled associations between elevated cadmium and accelerated biological age, as well as elevated selenium and lower biological age acceleration.

To get a better handle on how cadmium and selenium levels affect the pace of biological aging, Huang and colleagues performed further statistical analyses. These analyses suggested that blood cadmium levels accelerated biological age in a non-linear, J-shaped manner, where increased blood cadmium levels were exponentially associated with accelerated biological aging after exceeding certain levels. Moreover, blood selenium levels were associated with an L-shaped curve, where increasing blood selenium was associated with the most effective protection against biological aging when blood selenium levels were lower. These findings suggest that increased blood cadmium levels significantly accelerate biological aging, while increased blood selenium has a protective effect against biological aging.

To confirm an interaction where increased levels of selenium in the blood mitigate accelerated aging from elevated blood levels of cadmium, Huang and colleagues ran a joint analysis that compares study participants with varying blood levels of cadmium and selenium. As expected, they found that high levels of cadmium in the blood and low levels of selenium were associated with accelerated biological aging. However, in participants with elevated cadmium and selenium levels, no significant associations with accelerated aging were found. These associations suggest that elevated blood cadmium and low blood selenium lead to accelerated biological aging, but that elevated selenium, in addition to elevated cadmium, mitigates accelerated biological aging.

Because cadmium exposure has been associated with systemic inflammation, and since selenium may counteract this effect, Huang and colleagues ran statistical analyses to find how cadmium and selenium levels associate with markers of inflammation. The research group found that two markers of inflammatory processes—the lymphocyte-to-monocyte ratio and platelet-to-lymphocyte ratio—were associated with mediating the effects on biological aging of blood cadmium and selenium levels. Lymphocytes and monocytes are two types of white blood cells, and a low lymphocyte-to-monocyte ratio suggests a higher degree of systemic inflammation. Platelets are cell fragments in the blood that form clots to prevent bleeding, and a high platelet-to-lymphocyte ratio suggests that the body is undergoing an inflammatory response.

Along these lines, Huang and colleagues utilized mediation analyses to investigate the mechanism by which blood levels of cadmium and selenium influence biological age. These analyses suggested that lymphocyte-to-monocyte ratios and platelet-to-lymphocyte ratios mediate cadmium’s and selenium’s influence on biological age. In that sense, these findings suggest that cadmium increases inflammation to trigger accelerated biological aging and that selenium lowers inflammation.

Selenium Supplementation May Be Especially Important for Smokers

As suggested by the study, environmental cadmium exposure may increase systemic inflammation and accelerate aging, and increasing selenium in the blood, such as through supplementation, could counteract this effect. With a substantial percentage of people in the US exposed to the toxic metal cadmium through dietary sources, industrial processes, and cigarette smoke, getting a test for blood cadmium levels may be worthwhile.

If someone gets tested and has high blood levels of cadmium or believes they receive substantial cadmium exposure, selenium supplementation to counteract cadmium exposure is relatively affordable, costing anywhere between $5 to $20 for a month’s supply. Taking selenium supplements, as Huang and colleagues’ study suggests, may counteract the possible age-accelerating effects of elevated blood cadmium levels. This may be especially important for cigarette smokers, as cigarette smoking is associated with elevated blood cadmium levels.