In this study, researchers monitored blood flow in the brain among a group of 13 healthy volunteers while they sipped ice water with the straw pressed against their upper palates -- ideal conditions to bring on a brain freeze -- and while they drank room temperature water.
The people raised their hands once they felt a brain freeze coming on and then raised it again when the pain eased.
The results showed that one particular brain artery called the anterior cerebral artery expanded quickly due to a greater blood flow in conjunction with a brain freeze.
Researchers say the rapid changes in blood flow associated with brain freeze may be part of a natural survival mechanism.
"The brain is one of the relatively important organs in the body, and it needs to be working all the time," says researcher Jorge Serrador of Harvard Medical School in a news release. "It's fairly sensitive to temperature, so vasodilation might be moving warm blood inside tissue to make sure the brain stays warm."
Because the skull is a closed structure, Serrador says, the sudden influx of blood could raise pressure within the skull and cause the pain associated with brain freeze and other types of headaches.