See burning food (let's be honest, "well-done" means "over cooked") creates compounds known as glycotoxins.
In the first phase of the study, researchers found that mice raised on a diet high in glycotoxins (specifically a type called advanced glycation end products, or AGEs), "were more likely to develop dementia-like cognitive and movement problems as they aged than mice fed a low-glycotoxin diet," reports ScienceAlert.
These glycotoxin-munching mice also displayed increased amounts of amyloid beta proteins in their brains. These are the sticky proteins that are often found in the brains of people with Alzheimer's disease.
After lab trials on mice, the research team monitored the amount of AGEs in the blood of 93 New Yorkers aged over 60 for a period of nine months. They found that participants who ate more glycotoxins (i.e burned food) had more AGEs in their blood over the course of the study and thus experienced more cognitive decline than their peers.
Although this was a small study, the researchers believe there's enough evidence to suggest that eating rarer meat could offer a simple way to reduce the risk of dementia and metabolic syndromes as we age.