I recently discovered this forum, and I'm so grateful for the depth of investigation happening here. I'm a clinician and I regularly screen for B12 deficiency using serum B12, urinary MMA and homocysteine (as well as a CBC). Not surprisingly, I frequently discover deficiencies. Until recently I've been using the protocol described in Could it Be B12, with only limited success. After reading these threads, I'm beginning to understand why. I have a quick question: has anyone put together a bibliography of research studies that were reviewed to create the protocol described here? I'd love to read the original studies myself. Thanks again for making this information available to clinicians and patients.