Serum vitamin B12 levels and vitamin B12-binding proteins of serum and saliva of healthy Nigerians and Europeans

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Abstract
Serum vitamin B12 and unsaturated vitamin B12-binding capacity (UBBC) are known to be higher among people living in the tropics and subtropics than among Europeans. However, the cause of this phenomenon is not known nor have the individual transcobalamins (TC) been adequately examined. Therefore, we studied the serum vitamin B12, UBBC, and individual TC levels and salivary UBBC in 30 Nigerians and 10 Europeans living in northern Nigeria. Results have also been compared to those from white Americans living in the United States. The serum vitamin B12 tended to be higher in elite Nigerians than in the Europeans living in Nigeria, but there was considerable overlap. However, since all three groups in Nigeria had significantly higher levels than Americans an acquired cause associated with living in Africa is strongly suspected. No definite correlation with liver disease was apparent, but such an etiology could not be ruled out. The UBBC was clearly elevated in Nigerians compared to the Europeans, but UBBC and TC levels were indistinguishable between Europeans and Americans. TC I was higher in the Nigerians but the most striking difference was in TC II levels, which deserves further study. UBBC and TC values did not correlate with leukocyte counts or liver test results. It was not clear whether TC differences between Europeans and Nigerians were genetic or acquired. However, elevation of serum vitamin B12 and TC levels were independent of each other and probably had different causes.