A look at the literature, even if very prestigious, without a good grounding on the B12 issue will likely mislead if not out-and-out misinform.
I have found publications by physicians and large institutions (sometimes very prestigious) that continue to publish information that decades ago was debunked by mainstream research. In addition to that, it is easy to find medical literature containing misinformation that was never entertained as correct. This is a terribly neglected issue, even though a tremendous amount of research has been done over the decades.
Sadly, terminology from the 19th century was not changed after researchers found it incorrect. That fact makes a complicated issue even more difficult to straighten out. The most blatant example is the term "Pernicious Anemia." (Please see the homepage of this website for the Myth and Fact regarding "pernicious anemia." See Home Page )
When a doctor speaks of "pernicious anemia," what does that mean? I once had a substantial discussion with an MD about "pernicious anemia" vs megaloblastic anemia. When he later said he wanted to test for "pernicious anemia," I said: "Which one?" He said: "The real one." When I received a copy of the test results, he had tested for megaloblastic anemia. Aaaargh!
As if these problems were not enough, often even good medical literature implies that only elderly people are affected by malabsorption. This is not true, and until this gets through to more physicians, people young and middle-aged will continue to be damaged unnecessarily and often. In fact, there are defects that occur at birth.
Here are links to some exceptionally good medical articles:
This is an exceptionally up-to-date medical textbook chapter:
Goldman: Cecil Textbook of Medicine, 21st Ed., Copyright © 2000 (or 2004) W. B. Saunders Company. Chapter 163
Oral treatment is found superior to shots for many. Journal of the American Society of Hematology:
More to come...