M. Achón, E. Alonso-Aperte & G. Varela-Moreiras

Sección de Nutrición y Bromatología, Departamento de Ciencias Biomédicas I, Facultad de Ciencias Experimentales y Técnicas, Universidad San Pablo-CEU, 28668 Boadilla del Monte, Madrid, Spain

Correspondence to: María Achón y Tuñón, Sección de Nutrición y Bromatología, Departamento de Ciencias Biomédicas I, Facultad de Ciencias Experimentales y Técnicas, Universidad San Pablo-CEU, 28668 Boadilla del Monte, Madrid, Spain.
Telephone: 0034 91 3724006. Fax nº: 0034 91 3510475/96. E-mail: achontu@ceu.es

Background: Folate supplementation or food fortification is being nowadays recommended because of its effect on the prevention of neural tube defects and the lowering of homocysteine levels. We have previously reported a negative effect of high dose folate supplementation on dietary metabolic protein utilization in pregnant and virgin rats.
Objectives: To determine the effects of such folate supplementation on nutritional and some biochemical markers in aged rats.
Design: Aged male Wistar rats were given free access either to a folate supplemented diet (40 mg/kg diet) or a control diet (1 mg/kg diet) for 29 days following a week adaptation period. Two critical periods were used for metabolic balance studies (experimental days 1 to 8 and 22 to 29), involving the determination of digestive and metabolic protein utilization. Several biochemical markers involved in the methylation cycle were also determined.
Results: Data show that long term high folate supplementation reduces nitrogen digestive function in aged rats (P<0,03) during the second metabolic period (days 22 to 29). However, supplementation did not alter metabolic protein utilization. Plasma homocysteine and serum vitamin B6 and B12 levels, hepatic S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) concentrations -and thus methylation ratio, SAM/SAH-, were neither affected by folate supplementation.
Conclusion: Folate supplementation at high doses may have a negative effect on diet utilization, related to protein status.
Keywords: Folate; Methionine cycle; Aging; Toxicity