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High dietary folate supplementation: effects on diet utilization and methionine metabolism in aged rats
M Achon1, E Alonso-Aperts, G Varela-Moreiras
1Sección de Nutrición y Bromatología, Departamento de Ciencias Biomédicas I, Facultad de Ciencias Experimentales y de la Salud, Universidad San Pablo-CEU, 28668 Boadilla del Monte, Madrid, Spain. 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.