Vitamin B12 deficiency – the tip of an iceberg?
Of late, Vitamin B12 has become something of a cause celebre in the medical world. A deficiency of this vitamin has been long known to lead to the formation of bigger but less efficient red blood cells, a state known as Pernicious Anaemia (PA). ‘Pernicious’ because it is a condition which literally creeps up on the individual, under the radar so to speak, and is not always the first disorder that springs to the physician’s mind when someone presents with non specific symptoms such as tiredness and the like. Now there is increasing evidence that previously considered ‘normal’ levels are anything but, and that a lack of this vitamin may cause an array of symptoms (many seemingly unconnected) long before the blood cells show any sign of stress.
B12 is absorbed from the diet in the small intestine, from many food sources but most notably meats, so vegans in particular have always been at risk of deficiency. However, PA is seen when there is an inability to absorb Vitamin B12 from the gut – usually after the body destroys the very factor (known as ‘intrinsic factor’) that enables uptake from the small bowel. PA is an example of an autoimmune disease (one in which the body makes antibodies to its own tissues).
Fortunately, over that last century this has become a very treatable condition – lifelong B12 supplements given by injection will correct the deficiency and enable the individual to get back to normal life.
Over recent years, the level thought to represent the lower limit of normal has been challenged, and it would be fair to say that as a consequence the whole approach to the assessment of B12 and the threshold for intervention could be in need of revision. As many as 20% of those of us living in the developed world could have levels previously considered as acceptable
American Journal of Clinical Nutrition Feb 2009 vol 89 no 2 693-696