The salad leaf's iron-rich content may damage the brain similar to how the compound causes metal to rust, according to the researchers.
People with high levels of iron alongside the protein amyloid, which has previously been associated with Alzheimer's, are more likely to experience rapid cognitive decline, a study found.
Those with high amyloid but low iron levels are less at-risk of the disease, the research adds.
Removing such 'rust' from the brain could prevent or delay the degenerative condition, the researchers add.