Have you also checked out the book 'Eat Right for your Type' written by an ND? This is also worth a read and very good. I am blood group O positive and I was having problems eating wheat. Sure enough, I read the book and it said that people with blood group O should not be eating wheat. Since cutting it out of my diet I have had no further problems. So it does work and it well worth the read.
It's by Peter D'Adamo. He has several book out written more recently that reflect further research.
I also found some of the suggestions extremely helpful, including also avoiding wheat as much as possible (that wheat really is something, isn't? and who'd have thought it considering how prevalent it is?), but have been slow in becoming completely compliant. The more I work with it, though, the more I believe there really is something to it.
I follow it joyously and religiously and my health has never been better: normalised weight, smoother skin, stronger nails, quicker healing of wounds, more pinky complexion, greater immunity etc. etc.
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Turn the tap off before mopping up the mess
Eating Right For Your Blood Type 
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