I followed ER4YT for blood type A for 18 months...faithfully. I became diabetic eating that way. He says A's can't tolerate/digest animal proteins well. He does mention there are a few exceptions, and gives a general idea of what 'markers' indicate you are the exception. Well, my secretor status knocked out the first marker for an "O-like A" so I began the full A-type diet. Lots of veggies/fruits/high complex-high fiber starches/soy products/chicken & fish and rarely red meats. (But I 'craved' beef the whole time!) After discovering I was diabetic I embarked on the LC way of life. I went to a chiropractor/kineseologist who also believed in the ER4YT way of living and had him test me on lots of different foods. Well, in spite of at least one of my markers indicating I was NOT an O-like A, I obviously am. A's shouldn't be able to tolerate red meat--I not only tolerate it, I do better on it. If my blood sugar runs high I eat beef or bison--brings it right down (especially if I smother it in sauteed mushrooms) I was also tested on some things A's (and others) can't tolerate and I can't (such as liquid milk and concentrated tomato products) I can tolerate fermented milk products and a small fresh tomato occasionally. There are some other things. But I had my blood analyzed recently (I watched) and I could clearly see I am easily able to eat a great deal of animal protein (no 'sticky' red blood cells) So while I do agree with Dr. D'Adamo on blood type O and B (I have a friend who is a B and he was right on the money with her. She did SO much better following his advice, while I did not) I think he needs to do much more research on A's. He himself is a true A and his method works for him. I followed the forum for a long time and there were lots of other A's on there who were not doing well and didn't know why. My Dad was an A and was actually fairly typical according to Dr D's description--Dad loved veggies and rarely ate much meat. My Mom was an O and loved it--so did I. After reading his books I had concluded I was an O, before I even had my blood typed. Imagine my confusion when I learned I was an A. What was really wrong with me was that even as eating as an O, I was still eating too many carbs. I was (at that time) reactive hypoglycemic (precursor to diabetes, but docs didn't know that at the time--still don't even today) The *last* thing I needed to do was embark on a high-complex carb diet. Live and learn. I am still learning. So today I do a combination of LC/HP by way of Dr.Bernstein/Dr. Atkins modified by A-type/kineseologist tested food avoidances and a more 'alkaline' lifestyle (I drink lots of 'green' drink and add pH drops to my beverages to help keep me a little more alkaline)
...Summary, yes I think there is *something* to the blood type thing, but I wouldn't plunge into it wholeheartedly unless you are a B or an O.
...Sorry for the long post, but I feel very strongly about this. I'll be most happy to answer any ER4YT questions. I do feel it is a valid theory--giving up milk and nightshades was one of the best things I EVER did!