Low protein diets and blood coagulation.

half was casein would provide only 24 mg of phylloquinone Dear Dr. Visek: per kilogram of diet. In addition the 50 mg of menadione would I’m writing to comment on the paper entitled ‘‘Low dietary provide at most the equivalent of only 10 mg of phylloquinone protein impairs blood coagulation in BHE/cdb rats’’ by Chang to bring the total of 34 mg phylloquinone/kg. The fats used in et al. (1997). The BHE/cdb rat is a nonobese animal model this study are also low in phylloquinone and did not contribute of noninsulin-dependent diabetes mellitus that develops diabesignificantly to the vitamin K level. tes as it ages (Berdanier 1991). In the most recent AIN recommendation on the formulation These authors compared the effect of feeding a 50:50 mixof purified diets (Reeves et al. 1993) menadione was replaced ture of lactalbumin and casein at 8 g/100 g of diet with one by phylloquinone at 15 times the AIN-76 level which represents containing the same mixture at 38 g/100 g of diet to BHE/cdb an increase of about 75 times in biological activity. Although rats. After 4 weeks they observed that certain indices of blood the BHE/cdb rat may have a slightly different system for concoagulation (bleeding time, clotting time, prothrombin time, verting menadione to menaquinone-4, it is unlikely that any activated partial thromboplastin time and Factor VII activity) genetic difference accounts for the defect in coagulation. were abnormal in the rats fed the low protein diet. Since the abnormalities observed are consistent with a vitamin K Robert E. Olson deficiency, I looked further into the conditions of their experiDepartment of Pediatrics ments. University of South Florida I was surprised to note that the vitamin supplement which Tampa, FL 33606 these investigators used was the AIN-76 mixture which provides only 50 mg of menadione per kilogram of diet as a source of vitamin K. It is known that menadione (a vitamin K precurLITERATURE CITED sor) must be alkylated to form menaquinone-4 in order to American Institute of Nutrition (1977) Report of the AIN Ad Hoc Committee generate vitamin K activity (Dialameh et al. 1970), and that Standards for Nutritional Studies. J. Nutr. 107: 1340–1348. the overall conversion rate from isotopic studies varies from Berdanier, C. D. (1991) The BHE rat: an animal model for the study of noninsu1–5% (Dialameh et al. 1971). In addition, they found that lin-dependent diabetes mellitus. FASEB J. 5: 2139–2144.