The present invention relates generally to methods of inhibiting the onset and progression of Alzheimer's disease (AD), mild cognitive impairment (MCI), and related neurodegenerative disorders involving amyloidosis. The methods involve administering a composition comprising a therapeutically effective amount of D-pinitol to individuals who are at risk of developing the disease or have one or more symptoms of the disease. The invention also relates to methods of treating or preventing Alzheimer's disease or MCI that involve the use of such compositions. The invention further provides methods to promote the general health of the nervous system through administration of active ingredient compositions. The invention further relates to animal and cellular systems for the study of AD, MCI, and related disorders, and the identification of reagents useful in treating amyloidosis. The invention further provides methods to inhibit AD or MCI in an individual based on reducing caloric intake by the individual. The invention further relates to a method of treating or inhibiting an amyloidogenic disorder by caloric restriction.