spatts there may be something to it, based on acnecdotal evidence. It would be nice if there were some actual research out there, but at this point most scientist are not going to expend grant $$$ to research this. It seems unlikely that protien markers (or lack there of in the case of type O) on red blood cells would greatly impact the effects of micronutrients on the body. However, because there is something of a trend between higher percantages of blood types amoung different races, there may be a correlation between energy/bodyfat etc of different diets based on an ethnic group's eating habits over the last few thousand years. However, I tend to go with meat/green veggie diets if we look at it from a diet history perspective, because until the last few thousand years that was the diet of humans, and really we haven't had time to properly adapt to alot of the foods we eat as sources of food, from an evolutionary perspective. As far as the validity of the blood type diet? At this point, we just don't know. One could try it, see if it works or not, and go on from there.