A group of American researchers revealed that Alzheimer's disease could be linked with type 2 diabetes and went on to claim that the disease was nothing but 'brain diabetes' or type 3 diabetes.
This surprising new theory is offering hope that treatments already available for diabetes may also be able to help dementia sufferers, slowing down or stopping the progression of the disease, the Daily mail reported.
Cause of type 2 diabetes is known already - eating too much, especially junk food that's packed with sugar, refined carbohydrates and fat, which leads to damagingly high levels of sugar in the blood and high levels of insulin needed to clear it away.
The rising levels of glucose and insulin affect the blood vessels of the heart and extremities, potentially leading to blindness and amputations.
Now, scientists believe raised insulin levels also affect the brain.
Recent research has found this hormone plays a much more important role in the brain than once thought - protecting cells and helping to lay down memories.
In a study at Brown University in the U.S., when insulin supply in rats' brains was blocked - mimicking the effects of insulin resistance - the animals became disoriented and plaques appeared in their brain cells.
The effects of raised sugar are not limited to rats.
Last year, a small study from the U.S. Department of Veteran Affairs looked at healthy volunteers who had been on a junk-food diet for only four weeks.
They had a raised level of the markers for plaque in their spinal fluid.
Scientists are still finding out what happens when insulin levels in the brain rise.
"But we know it is much more important than we thought," the paper quoted Professor Jennie Brand-Miller, a biochemist at the University of Sydney and world authority on insulin (she helped develop the glycaemic index), as saying.
High levels of insulin could also be having a damaging effect on neurons, she said.
"This is because insulin comes partnered with another hormone, amylin, which makes the same sort of plaques as those found in the brains of dementia patients, except in the pancreas. It could be contributing to plaque formation in the brain," she explained.
High sugar levels don't just push up insulin - they can also damage the brain directly.
Last May, researchers at the University of California showed for the first time that eating high levels of fructose, the concentrated sweetener found in many processed foods, reduced brain function in rats.
"A high fructose diet over the long term alters your ability to learn and remember information," said research leader, Fernandez Gomez-Pinilla, a professor of neurosurgery.
Earlier this year, an Australian team scanned the brains of 300 older people who didn't have dementia.
The brains of those with diabetes shrank up to two-and-a-half times faster than normal.
This shrinking occurred most in the frontal lobe that controls many functions damaged by Alzheimer's - decision-making, emotional control and long-term memory.