The dark coloring on hard anodized pans is just that...coloring. Calphalon recommends a cleanser for their hard anodized pans. Dishwasher washing is not recommended because of the force of the small cleaning pellets and the fact that it is a lye solution (base oposite ph of an acid) may begin to break down the anodization which is an electro acid bath process. Lye also affects the look of AllCald's copper, and brushed aluminum exteriors.
Polished aluminum pans, used in 85% of the worlds' restaraunts including America's are safe if seasoned, and properly cleaned, and the food doesn't sit and cool in them, same as it shouldn't in raw cast iron.
The Alzheimer's threat is not current concern from everything I've read.
If you worry about the reactions of food to metals you cook with, cook only in soapstone. It is the only totally non reactive cooking pot substance. (Stainless reacts to salts, contains chromium and nickel.)