Is your pernicious anemia due to lack of or mutated intrinsic factor?

Do you feel tired and weak all the time? You should find out if you have pernicious anemia. The blood disorder occures when you can’t make enough red blood cells to take oxygen to your cells due to lacking B12.

Lack of B12 in the diet may be due to lack of intrinsic factor. To understand how this might happen, it’s important to understand just how cobalamin is absorbed. Cobalamin (B12) is taken up by R-binder, found in the saliva, after its released in the stomach from meat and dairy products that you eat (1). The bound complex then gets to the intestine where the cobalamin is released and binds to intrinsic factor (1). Cobalamin needs intrinsic factor to be absorbed because absorption only occurs when intrinsic factor binds to receptors of the distal ileum. Then cobalamin is released and taken up by a transport protein called transcobalamin II (1).

The lack of intrinsic factor can be caused by an autoimmune attack on intrinsic factor and the parietal cells producing it (1). Or it may be due to a possible mutation of intrinsic factor caused by mutation of intrinsic factor gene(2). In either case, dietary B12 from meat and dairy is unlikely to help with the anemia (1). B12 injections or sublingual dosages are necessary.


1. Nowak TJ, Handford AG. Pathophysiology: Concepts and Applications for Health Professionals. New York: McGraw-Hill, 2004.

2. Remacha AF, Del RE, Sarda MP, Canals C, Simo M, Baiget M. Role of (Glu –> Arg, Q5R) mutation of the intrinsic factor in pernicious anemia and other causes of low vitamin B12. Ann Hematol 2008;87:599-600.

Published by David Despain, MS, CFS

David is a science and health writer living on Long Island, New York. He's written for a variety of publications including Scientific American, Outside Online, the American Society for Nutrition's (ASN) Nutrition Notes Daily, and Institute of Food Technologists' (IFT) Food Technology magazine and Live! blog. He's also covered new findings reported at scientific meetings including Experimental Biology, AAAS, AOCS, CASW, Sigma Xi, IFT, and others on his personal blog "Evolving Health." David is also an active member of organizations including the National Association of Science Writers (NASW), the American Association for the Advancement of Science (AAAS), the American Society for Nutrition, the Institute of Food Technologists, and the National Audubon Society. David has a master's degree in human nutrition from the University of Bridgeport, and a bachelor's degree in English from University of Illinois at Springfield. He also earned his Certified Food Scientist credential from the Institute of Food Technologists.

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