If High Folic Acid Aggravates Vitamin B₁₂ Deficiency What Should Be Done about It?

Abstract

The most common cause of vitamin B₁₂ deficiency in older people is malabsorption of food-bound vitamin B₁₂. Thus, it is suggested that the recommended daily allowance of 2.4 μg/d be met primarily with crystalline vitamin B₁₂, which is believed to be well absorbed in individuals who have food-bound malabsorption. There is concern that high intakes of folic acid from fortified food and dietary supplements might mask the macrocytic anemia of vitamin B₁₂ deficiency, thereby eliminating an important diagnostic sign. One recent study indicates that high serum folate levels during vitamin B₁₂ deficiency exacerbate (rather than mask) anemia and worsen cognitive symptoms. Another study suggests that once vitamin B₁₂ deficiency is established in subjects with food-bound malabsorption, 40 μg/d to 80 μg/d of oral crystalline vitamin B₁₂ for 30 d does not reverse the biochemical signs of deficiency. Together, these studies provide further evidence that public health strategies are needed to improve vitamin B₁₂ status in order to decrease the risk of deficiency and any potentially adverse interactions with folic acid.

cognition, fortification, homocystein