Letters

RAPID RESPONSE FROM BMJ.COM

As of June 24, three rapid responses had been posted on bmj.com concerning the paper by Rushton et al, along with a reply from the authors. Below we've reproduced a portion of one of the responses; the references have been omitted, but they may be found on the web (http://bmj.com/cgi/eleters/322/7298/1355).EDITOR

Iron status in women of childbearing age

This article originally appeared in BMJ USA

EDITORRushton et al suggest that male reference ranges for ferritin and hematological parameters should be used when assessing iron status in women of childbearing age. However, the authors make some incorrect assumptions and fail to consider the practical implications of such a change.

No one disputes the fact that women need to have sufficient iron stores to prevent iron deficiency in the face of a physiological challenge such as pregnancy or blood loss. However, as far as we are aware, there is no proven benefit to having a higher iron status. In fact, there may be some health risks. While suggestions that higher iron status may actually increase risk of coronary heart disease are now being questioned, there is evidence to suggest that a high iron intake may increase risk of colorectal cancer. Moreover, one in 150 people in the United Kingdom are homozygous for the C282Y mutation of the HFE gene, which is associated with hemochromatosis. Although the clinical penetrance of this genotype appears to be lower than was originally thought, any widespread measures to increase the iron intake of women of childbearing age are likely also to increase the intake of men and of postmenopausal women. It is therefore particularly important that any changes to the lower limits of iron status indices be firmly supported by clinical and experimental evidence.

It is important to ask what the practical implications would be of raising the lower limits for iron status indices in women to those applied to men. The median value for hemoglobin concentration in UK women of childbearing age is 132g/L. Increasing the lower cut-off to 130g/L, in line with the male figures, would therefore define half the pre-menopausal adult female population of the UK as anemic! How would the iron intake of all these women be increased? A recent dietary intervention study in 22 pre-menopausal women with serum ferritin <20mcg/L has shown that highly motivated persons who are mildly iron deficient may be able to use diet to improve their iron status. However, this study also showed that supplementation is likely to be a more practical option for most women because of the wide range of behavioral changes required in order to not just increase iron intake, but also to increase intake of iron absorption enhancers (such as meat and vitamin C-containing foods), and decrease intake of inhibitors (such as phytate in wholegrain cereals, and tannins in tea and coffee). Iron supplementation is known to produce unpleasant side effects in a significant proportion of individuals, so any program involving the use of iron supplements would be likely to have a detrimental effect on the well-being of a significant number of women.

Anne-Louise M Heath, postdoctoral fellow. 
Susan Fairweather-Tait, head of division. 
Institute of Food Research, Norwich, UK

Mark Worwood, professor. 
Department of Haematology, University of Wales College of Medicine, Heath Park, Cardiff, UK