ANN ARBOR, Mich. — Most people are aware of the many harmful chemicals in a cigarette, but few would expect to find those toxins in their food. A new study finds people with high levels of cadmium, a toxic chemical element, are at higher risk of dying from the flu or pneumonia. Researchers at the University of Michigan School of Public Health warn smokers aren’t the only people being exposed to cadmium. The toxin is also present in contaminated vegetables, grains, and even animal products too.
“Our study suggests the public in general, both smokers and nonsmokers, could benefit from reduced exposure to cadmium,” says lead author Sung Kyun Park in a university release.
Cadmium is a naturally occurring metal and commonly used to make batteries and solar cells. Unfortunately, the metal can also seep into the ground and water sources through pollution. Researchers say long-term exposure to the metal can impact a person’s immune system, especially in the lungs. Along with finding evidence cadmium exposure makes flu and pneumonia much worse, study authors suspect it may also worsen the symptoms of COVID-19.
“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,” adds senior author Howard Hu from the University of Southern California. “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.”
Linking cadmium to COVID
Researchers say that early on in the pandemic, a large number of the people dying in Wuhan, China were older patients, men, and smokers. These findings prompted Finnish researcher and study co-author Matti Sirén to contact Park and Hu. The American researchers had already conducted a study on cadmium exposure and chronic diseases a decade earlier.
Since data linking cadmium exposure and coronavirus would be limited in 2020, the team focused on finding a connection between the metal and similar viral infections instead. The new study examined nearly 16,000 people who took part in the U.S. National Health and Nutrition Examination Survey from 1988-1994 or 1999-2006.
The first survey measured cadmium levels through urine samples while the later survey took blood samples. Since tobacco products contain over 3,000 different chemicals in them, researchers made sure to look at cadmium levels in non-smokers as well. The study also adjusted the results to account for differences in age, sex, race, weight, cholesterol, and blood pressure readings.
The results reveal patients with cadmium levels in the 80th percentile (meaning cadmium levels higher than 80 percent of all other patients) are 15 percent more likely to die from the flu or pneumonia compared to patients in the bottom 20 percent of cadmium exposure.
Among non-smokers only, patients with the highest levels of cadmium exposure are 27 percent more likely to die from a viral infection than those with lower levels.
“We couldn’t directly look at cadmium body burden among COVID-19 patients in the early pandemic,” Park explains. “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.”
Making lifestyle changes to prepare for another pandemic
Researchers warn that COVID-19 may not be a one-time crisis. They add that reducing cadmium exposure now can help defend against future illnesses when they come. Park advises smokers to quit the habit.
The study also urges people to take note of where cadmium exposure can come from in food. Cereal, rice, animal organs like liver and kidneys, soybeans, and some leafy vegetables are all potential sources of cadmium contamination. Researchers recommend looking for dietary alternatives like cabbage and broccoli, which have high levels of antioxidants but generally low levels of cadmium.
“This isn’t a recommendation for a draconian change in lifestyle, since many of these foods are typical staples of a balanced, nutritious diet, and their overall contribution to cadmium burden is likely modest,” Hu says. “Rather, the suggestion is to consider some shifts in choices. Increased scrutiny is needed of sources of cadmium exposure and surveillance of cadmium levels in the general population, and policymakers need to work on continuing to reduce environmental cadmium pollution.”
The study appears in the journal Environmental Health Perspectives.