Higher Vitamin D Dietary Intake Is Associated With Lower Risk of Alzheimer's Disease: A 7-Year Follow-upImportant to note that this study was done in France latitude 47 and the increased incidence of AD was in those getting less than 2000iu/d People living further North than lat 47 will require significantly more. 1000iu per 25lbs is generally regarded as an appropriate amount.

Article on the same story here
Higher Vitamin D Dietary Intake Is Associated With Lower Risk of Alzheimer's Disease: A 7-Year Follow-up.

very interesting, because it specifically stated those who did not take the vitamin D supplement. Sometimes I think people are going outside are getting more sun, have a better social life, maybe they get vitamin D through their food. But this clearly indicates from a supplement, which I find really interesting.

Eating fish may reduce risk of Alzheimer's by lowering levels of protein linked to the disease
Daily Mail article on the fact OMEGA 3 also helps clear amyloid-β peptide

We know the active form of vitamin D does this
1α,25-Dihydroxyvitamin D3 enhances cerebral clearance of human amyloid-β peptide

and we also know Omega 3 DHA acts (like Curcumin) as a vitamin d receptor ligand so enhancing the actions of the active form of D3..

In the UK a typical 125g can of sardines contains around 600iu of D3 and 2grams omega 3 though probably only a third of that is DHA and 2 thirds EPA. While the 600iu of vitamin D would be a significant part of most peoples daily vitamin d intake it's only a small fraction of the vitamin D full body sun exposure would create. So correcting vitamin D status to optimum levels (50~60ng/ml 125~150nmol/l would require more like 1000iu per 25lbs you weigh. and while 2g of omega 3 is a significant amount it's not likely folks are going to eat a whole 125g can of sardines every day of the year, even twice weekly would be a huge improvement.
But really we need to reduce the OMEGA 6 intake from corn, soy, sunflower, safflower cottonseed oils. It's the fact there is 20 times too much omega 6 that prevents omega 3 resolving inflammation.

Omega-3s Linked to Lower Amyloid Levels Medpage today on same research.

Abstract here but I can't get the full text.
One of the other authors has a recent presentation online on Nutritional strategies that may delay/prevent AD
Dietary Intervention – Evidence in AD –How can we improve? this covers some of the basics but I've had a quick skim and didn't see vitamin D3 nor any mention of Resveratrol..