Reply to K Hendricks

University of Florida Institute of Food and Agricultural Sciences Food Science and Human Nutrition Department PO Box 110370 Gainesville, FL 32611-0370 E-mail: jfgy{at}ufl.edu

Dear Sir:

Hendricks raises the question of whether in our recent study of folate absorption the women who had given birth to infants with a neural tube defect (NTD) may have malabsorbed folate as a result of a parasitic infestation (of terrestrial origin, one would suspect). She also incorrectly interprets our data as indicating a selective malabsorption of polyglutamyl folates.

In fact, we reported reduced urinary excretion of labeled folates derived from oral doses of both mono- and polyglutamyl folate, which we interpreted as being the result of less efficient intestinal transmural transport. We recognize that differences in in vivo retention or extent of catabolism may also have existed between the women with NTD-affected pregnancies and the control women. The protocol used in our study involved saturating the subjects with folic acid to enhance excretion of the newly absorbed folate from the test doses. It is highly probable that this protocol was a specific means of testing for differences in the extent of absorption because the saturation protocol would minimize any differences in postabsorptive processing of labeled folates.

Whether the women with NTD-affected pregnancies had a parasitic infestation during our study cannot be determined; however, such an infestation is unlikely because all women were in good health and exhibited no evidence of gastrointestinal problems. Thus, it is unlikely that intestinal parasites or pathogens, whether bacterial, protozoan, or helminthic, were present in our case subjects in amounts that would have significantly impaired folate absorption.

Hendricks's suggestion that fecal samples be fractionated and analyzed is interesting to consider but would have been impractical in our study. Any unabsorbed, labeled folate would be subject to cellular uptake, metabolism, and potential catabolism by colonic microorganisms. In addition, labeled colonic folates would be diluted extensively with unlabeled folates produced by the colonic microflora. All of these factors would reduce the feasibility and complicate the interpretation of fecal folate analysis in this protocol. In summary, we thank Hendricks for her comments and recognize the need to investigate folate absorption and metabolism more thoroughly in women with a history of NTD-affected pregnancies.