There are many nutrition books and websites (like http://www.aqua4balance.com/Healthy-Diet/blood-type-nutrition-educational-workshop.html) that assign very different nutritional needs to individuals with different blood types. Example: individuals with type O are said to require more high protein (e.g. red meat) in their diet and be relatively lactose intolerant, etc. The differences between blood types in these various books are relatively consistent with each other and they usually give a kind of 'evolutionary' explanation for the diet needs, e.g. O blood types are "hunters" ancestrally who are very carnivorous.
Is there any biological/molecular basis to these differences? Is there any scientific basis for thinking that individuals with a genome of a particular blood type really do require more B12/meat/highprotein and are somehow deficient in processing dairy products? Or is this at the level of slightly more sophisticated astrology?