Back in 2005, a published medical paper introduced a new disease tentatively dubbed "type 3 diabetes".
The researchers learned that, in addition to the pancreas, your brain also produces insulin.
They discovered that without the insulin your brain cells will die.
A drop in insulin production in your brain may contribute to the degeneration of your brain cells, and studies have found that people with lower levels of insulin and insulin receptors in their brain often have Alzheimer's disease.
Studies since 2005 have continually documented that insulin has a much greater role in the brain than previously expected.
Insulin is directly responsible for neuron glucose-uptake, and the regulation of neurotransmitters like acetylcholine, which are crucial for memory and learning.
Scientists have come to understand that cognition is impaired when insulin levels are reduced.
The clinical research has made it quite clear that the same pathological process that leads to insulin resistance and type 2 diabetes may also hold true for your brain.
The take away from these studies make a strong point that the over-consumption of sugars and "grains" which are also detrimental to the the development of diabetes may also result in Type 3 Diabetes (brain diabetes).
When the brain becomes overwhelmed by the consistently high levels of glucose, the insulin signaling will eventually become blunted or desensitized. This will lead to impairments in your thinking and memory abilities, eventually causing permanent brain damage.
Steen E, Terry BM, Rivera EJ, Cannon JL, Neely TR, Tavares R, Xu XJ, Wands JR, de la Monte SM. Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer's disease--is this type 3 diabetes? J Alzheimers Dis. 2005 Feb;7(1):63-80.
de la Monte, Wands.Alzheimer's Disease Is Type 3 Diabetes–Evidence Reviewed, J Diabetes Sci Technol. 2008 Nov; 2(6): 1101–1113.