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Macrocytic anaemia status does not change in response to a physiological dose of folic acid in persons with suboptimal vitamin B12 status

Published online by Cambridge University Press:  09 September 2010

K. M. Mooney
Affiliation:
Liverpool Hope University, Hope Park, Liverpool L16 9JD, UK
G. J. Cuskelly
Affiliation:
Queen's University Belfast, Institute of Agri-Food and Land Use, School of Biological Sciences, David Keir Bldg, Belfast BT9 5AG, UK and
I. Young
Affiliation:
School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast BT12 6BJ, UK
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Abstract

Type
Abstract
Copyright
Copyright © The Authors 2010

Mandatory folic acid fortification has been advocated as the most effective method of protecting against neural tube defect pregnancies on a population basis(Reference Oakley1). Most European countries have not proceeded due to concerns of putative masking of vitamin B12 deficiency. However, it is currently unknown what dose of folic acid masks vitamin B12 deficiency.

The aim of this study was to assess the effect of a physiological dose of folic acid (400 μg/d) on the haematological profile of those with suboptimal vitamin B12 status. Participants with serum vitamin B12 levels between 130 and 200 ng/l were given either folic acid or placebo daily for 6 months in a randomized, double-blind, placebo-controlled study. Fasting blood samples were collected pre-intervention and at monthly intervals until completion to determine vitamin B12, folate and haematological status (mean cell volume, Hb and haematocrit).

Fourteen volunteers in the placebo group and 15 volunteers in the folic acid group completed the 6-month intervention. Volunteers who were Fe-deficient were excluded from analysis. There were no significant differences in vitamin B status and haematological markers between groups pre-intervention. Significant responses to intervention occurred in serum folate (increased; P<0.001), red blood cell folate (increased; P=0.001) and plasma homocysteine (decreased; P=0.011) in the folic acid group. Consumption of 400 μg of folic acid per d had no significant effect on haematological profile. The table shows the numbers of volunteers who were defined as having a normal haematological status at each stage of intervention in each group.

NS: non-significant. McNemar's test was used to determine differences in haematological status pre- and post-intervention within groups (P<0.05).

This is the first folic acid supplementation trial in persons with apparent suboptimal vitamin B12 status. Both groups had a normal haematological profile pre-intervention suggesting that mean cell volume should not be the sole diagnostic marker used to identify possible vitamin B12 deficiency.

References

1.Oakley, GP Jr. (1997) Let's increase folic acid fortification and include vitamin B-12. Am J Clin Nutr 65, 18891890.CrossRefGoogle ScholarPubMed