APOE and Mental deterioration: Epidemiologic studies suggest that a diet rich in fish is associated with less cognitive decline[16] and with a decreased risk of Alzheimer's disease.[17] The benefits may be specific to the intake of fatty fish, such as tuna, and may be evident only in those who are negative for the apolipoprotein E (ApoE) epsilon 4 allele.[18] Regular fruit and vegetable intake, even in the form of juices, has also been associated with a decreased risk of Alzheimer's disease.[19]