" There is now good dietary information for the two chief conditions referring to mental decline. On the modest side, there is a condition called "cognitive impairment" or "cognitive dysfunction." This condition
describes the declining ability to remember and think as well as one once did. It represents a continuum of disease ranging from cases that
only hint at declining abilities to those that are much more obvious and easily diagnosed.
Then there are mental dysfunctions that become serious, even life threatening. These are called dementia, of which there are two main types: vascular dementia and Alzheimer's disease. Vascular dementia is primarily caused by multiple little strokes resulting from broken blood vessels in the brain. It is common for elderly people to have "silent" strokes in their later years. A stroke is considered silent if it goes undetected and undiagnosed. Each little stroke incapacitates part of the brain. The other type of dementia, Alzheimer's, occurs when a protein substance called beta-amyloid accumulates in critical areas of the brain
as a plaque, rather like the cholesterol-laden plaque that builds up in cardiovascular diseases. "

― T. Colin Campbell , The China Study: The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss, and Long-term Health