A progressive neurodegenerative disorder and the most common cause of dementia, marked by the accumulation of amyloid plaques and tau tangles that destroy neurons in memory and reasoning centers of the brain. It typically begins with forgetfulness and difficulty forming new memories, advancing over years to disorientation, personality change, and loss of independence. While age and genetics dominate risk, research increasingly implicates modifiable factors: cardiovascular health, physical activity, and dietary patterns such as the Mediterranean and MIND diets are associated with lower risk, possibly by protecting blood vessels and reducing inflammation. No diet prevents or cures it, and claims to the contrary should be treated skeptically. Nutritional care focuses on maintaining weight and hydration as the disease erodes the ability to eat, a major challenge for caregivers.