According to a doctor's column in the Idaho Statesman, proton pump inhibitors [Nexium, Pevacid, Prilosec, etc] make it difficult for people to absorb B12 from food and hard to absorb calcium. Apparently PPIs do not effect the absorption of B12 oral supplements. Read the short article here:
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CD, Ankylosing Spondylitis, lupus, small fiber peripheral neuropathy, avascular necrosis, peripheral artery disease, degenerative disc disease, and a host of other medical problems.