Old age and chronic health conditions aren't the only risk factors for serious COVID-19 infection. Researchers say people with high levels of the heavy metal cadmium may also have higher odds of severe disease during the pandemic.
Cadmium is found in cigarettes and in contaminated vegetables. Previous research has shown that long-term exposure to cadmium, even at low levels, may weaken the lungs' defense system.
"Our study suggests the public in general, both smokers and nonsmokers, could benefit from reduced exposure to cadmium," said study co-author Sung Kyun Park. He's an associate professor of epidemiology and environmental health sciences at the University of Michigan School of Public Health, in Ann Arbor.
This study found that people with high levels of the chemical have higher death rates from respiratory viruses, such as the flu and pneumonia, suggesting they may also be more vulnerable to COVID-19.
The researchers analyzed data from nearly 16,000 people who took part in the U.S. National Health and Nutrition Examination Survey from 1988-1994 and 1999-2006.
Cadmium was measured in urine in the first survey and in blood in the second. After adjusting for a number of factors, the investigators found that patients with cadmium levels in the 80th percentile were 15% more likely to die of influenza or pneumonia than those in the 20th percentile.
Among those who never smoked, the difference was even greater, with a 27% higher risk of death among those in the 80th percentile than those in the 20th percentile, according to the study.
The report was published in the December issue of the journal Environmental Health Perspectives.
"We couldn't directly look at cadmium body burden among COVID-19 patients in the early pandemic," Park said in a university news release.
"Our motivation was to find a modifiable risk factor that can predispose people with COVID-19 infection to develop a severe complication and die of COVID-19," Park added. "COVID-19 may not be a one-time event. Our findings suggest that the public can benefit from reduced cadmium exposure when the next pandemic occurs. This cannot be done suddenly and takes time through policy changes."
Smokers should stop smoking, and everyone should know about major sources of cadmium in their diet: cereal, rice, animal organs such as the liver and kidneys, soybeans and some types of leafy vegetables, Park said.
There are other vegetables you can eat instead, he suggested.
For instance, cabbage and broccoli and other cruciferous veggies contain high levels of antioxidants but relatively low levels of cadmium.
According to study senior author Howard Hu, "The associations we found need to be verified in other populations and also studied with respect to cadmium's potential impact on COVID-19-related morbidity and mortality." Hu is a professor and chair of preventive medicine at the University of Southern California, and an occupational/environmental physician.
"Unfortunately, the human body finds it much more difficult to excrete cadmium than other toxic metals, and its presence in many nutritious foods means it is critical to continue reducing sources of environmental pollution that contribute to its presence in air, soil and water," Hu added.
The U.S. Centers for Disease Control and Prevention has more on cadmium.
SOURCE: University of Michigan, news release, Dec. 16, 2020