Reply to NJ Wald et al

Green College
Oxford OX2 6HG
United Kingdom
E-mail: john.grimleyevans{at}geratol.ox.ac.uk

Robert Clarke

Clinical Trial Service Unit
University of Oxford
Oxford
United Kingdom

Dear Sir:

We reject all 3 accusations of error made by Wald, Law, and Hoffbrand. Where there is even a remote possibility of harm from a public health intervention, the burden of proof lies with those who choose to assert that harm could not result. What has happened in the United States at one level of folic acid fortification is not necessarily helpful in predicting what might happen in the United Kingdom at a higher level and where the medical condition of older people, including their vitamin B-12 status, may be less well documented.

Wald et al are incorrect in asserting that the Committee on Medical Aspects of Food and Nutrition Policy (COMA) Report (1) made a "recommendation" about fortification. For reasons set out in the preface to the Report, recommendations would have been improper; the Committee's task was to appraise options. The modeling that was set out in the Report evaluated several possible levels of fortification as targets to be attained but not exceeded (paragraph 9.5.10). For each target, the number of neural tube defects likely to be prevented and the proportion of older people exposed to total daily folate intakes in excess of 1 mg were estimated. There would have been no sense in calculating the latter values if the Committee had expected fortification levels to be treated as minima or as merely approximate.

The need to protect older people with undiagnosed vitamin B-12 deficiency as part of "any general policy to increase dietary folic acid consumption" is clearly and repeatedly expressed in the Report. We and others have been exploring ways and means of implementing such protection. We anticipate that sufficient data will soon be available to develop a rational approach to the issue in the United Kingdom, so that the 2 public health measures alluded to in Wald et al's final sentence could go forward in concert.

REFERENCE

1. Committee on Medical Aspects of Food and Nutrition Policy. Folic acid and the prevention of disease. London: The Stationery Office, 2000.