Please consider that the following article is hypothetical. It is based on research, however.
Based on things that I have read, there are natural ways to prevent Alzheimer's. It takes some information synthesis to get there, so please hang-on. The most amazing link that has been found is a relationship between the herpes simplex virus type I (HSV-I) and Alzheimer's amyloid plaques. The article can be found summarized at www.sciencedaily.com/releases/2008/12/081207134109.htm The team conducting the research discovered that HSV-I DNA is "located very specifically in 90% of plaques in Alzheimer's disease sufferer's brains" (Wozniak, Mee, and Itzhaki, 2008).
The researchers hypothesized that antivirals can be used to inhibit the harmful consequences of HSV-I action. However, there is another, more inexpensive and effective possibility. The amino acid L-lysine has been demonstrated to inhibit HSV-I (Griffith, 1987, 1978; Kagan, 1974). The naked virions of HSV-I contain protein VII, which is arginine rich, at the core. The virions contain significantly less lysine (Olshevsky and Becher, 1970). Adding lysine inhibits viral replication.
Now, the logical conclusion needs to be investigated. It is a reasonable proposition that prophylatic loading of L-lysine in people who have the genetic prospect of developing Alzheimer's. Further, people with a history of HSV-I outbreaks as cold sores need to be investigated as potential subjects for such a study.
Griffith, R. S. (1987). Success of L-lysine therapy in frequently recurrent herpes simplex infection. Dermatologica 175 183-190.
Griffith, R. S. (1978). A multi-centered study of lysine therapy in herpes simplex infection. Dermatological 156 257-267.
Kagan, C. (1974). Lysine therapy for herpes simplex. The Lancet 1 137.
Olshevsky, V. & Becher, V. (1970). Virology 40 948.
Wozniak, M. A., Mee, A. P. & Itzhaki, R. F. (2008). Herpes simplex virus type I DNA is located within Alzheimer's disease amyloid plaques. The Journal of Pathology 217(1), 131-138.