A toxic metal used in MRI scans may pose greater health risks than previously known, especially in people who consume foods or supplements with oxalic acid.
Scientists found that oxalic acid can trigger the formation of gadolinium nanoparticles inside the body—particles linked to severe, sometimes deadly conditions like nephrogenic systemic fibrosis. The team is working to identify who’s most vulnerable and how to reduce the danger, potentially reshaping safety protocols for a common medical procedure.
A Common MRI Metal Raises Alarming Questions
Researchers at the University of New Mexico have found that oxalic acid, a compound found in foods like spinach, nuts, and chocolate, can trigger the formation of toxic metal nanoparticles in the body. The metal in question is gadolinium, a rare earth element commonly used in MRI scans to enhance image clarity.
In a new study published on March 8 in Magnetic Resonance Imaging, a team led by Dr. Brent Wagner, professor of Internal Medicine at the UNM School of Medicine, investigated how these gadolinium nanoparticles form. Their findings could help explain how exposure to the metal leads to serious health problems, particularly in the kidneys and other organs.
The Devastating Impact of Gadolinium Exposure
“The worst disease caused by MRI contrast agents is nephrogenic systemic fibrosis,” he said. “People have succumbed after just a single dose.” The disease causes thickening and hardening of the skin, lungs, and heart, and can lead to painful joint contractures.
Gadolinium-based contrast agents are injected prior to MRI scans to help create sharper images, Wagner said. They are typically considered safe because the metal is tightly bound to other molecules and usually excreted from the body. Most people have no side effects. However, previous studies have shown that gadolinium particles can remain in the brain, kidneys, blood, and urine for years, even in people who show no symptoms.
Why Some Get Sick and Others Don’t
Scientists are left with intertwined puzzles: Why do some people get sick, when most don’t, and how do gadolinium particles become pried loose from the other molecules in the contrast agent?
“Almost half of the patients had been exposed only a single time, which means that there’s something that is amplifying the disease signal,” Wagner said. “This nanoparticle formation might explain a few things. It might explain why there’s such an amplification of the disease. When a cell is trying to deal with this alien metallic nanoparticle within it, it’s going to send out signals that tell the body to respond to it.”
“This nanoparticle formation might explain why there’s such an amplification of the disease. When a cell is trying to deal with this alien metallic nanoparticle within it, it’s going to send out signals that tell the body to respond to it.”
Brent Wagner, MD, Professor, Department of Internal Medicine in the UNM School of Medicine
Oxalic Acid: A Dietary Trigger?
In their study, Wagner’s team focused on oxalic acid, which is found in many plant-based foods, including spinach, rhubarb, most nuts and berries, and chocolate, because it binds with metal ions. The process helps lead to the formation of kidney stones, which result when oxalate binds with calcium. Meanwhile, oxalic acid also forms in the body when people eat foods or supplements containing vitamin C.
In test tube experiments the researchers found that oxalic acid caused minute amounts of gadolinium to precipitate out of the contrast agent and form nanoparticles, which then infiltrated the cells of various organs.
Why One Body Suffers and Another Doesn’t
“Some people might form these things, while other do not, and it may be their metabolic milieu,” Wagner said. “It might be if they were in a high oxalic state or a state where molecules are more prone to linking to the gadolinium, leading to the formation of the nanoparticles. That might be why some individuals have such awful symptoms and this massive disease response, whereas other people are fine.”
Toward Safer MRI Practices
The finding points to a possible way to mitigate some of the risks associated with MRI scan, he said.
“I wouldn’t take vitamin C if I needed to have an MRI with contrast because of the reactivity of the metal,” Wagner said. “I’m hoping that we’re getting closer to some recommendations for helping these individuals.”
The team is now researching ways to identify those who might be at greatest risk from gadolinium contrast agents. In a new study, they’re building an international patient registry that will include a collection of blood, urine, fingernail, and hair samples, which could provide evidence of gadolinium accumulation in the body.
“We want to get a lot more information to come up with the risk factors that relate to those with symptoms,” he said. “We’re going to ask about what medical conditions you had at the time of exposure, what medications are you on, and we want to include dietary supplements, because that might piece it all together – why some people have symptoms, whereas others seem to be impervious.”
Reference: “Precipitation of gadolinium from magnetic resonance imaging contrast agents may be the Brass tacks of toxicity” by Ian M. Henderson, Angelica D. Benevidez, Curtis D. Mowry, John Watt, George D. Bachand, Martin L. Kirk, Karol Dokładny, Joshua DeAguero, G. Patricia Escobar and Brent Wagner, 8 March 2025, Magnetic Resonance Imaging.
DOI: 10.1016/j.mri.2025.110383
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