Intake of folic acid (FA) in very high amounts leads to conditions similar to those of metabolic deficiency in folate(1). In a similar way, vitamin B12 status influences the physiological response to different FA doses in the organism(2). Several studies relate both the shortage of folate as well as its excess with a change in the immune response(3). Similarly, it has been found that vitamin B12 may play an important role in cellular immunity. Therefore, an imbalance between the status of vitamin B12 and FA could exacerbate the immune response(4).
The aim of this study was to evaluate the global effect of different levels of dietary FA and vitamin B12 on several parameters of the immune response in aged rats.
Twenty-month male Sprague–Dawley rats (n=40) divided into four groups were fed during 30 days with differently supplemented diets:
CONB12/CONFA (50 μg vitamin B12; 2 mg FA)
DEFB12/DEFFA (0 μg vitamin B12; 0 mg FA)
DEFB12/CONFA (0 μg vitamin B12; 2 mg FA)
DEFB12/SUPFA (0 μg vitamin B12; 8 mg FA)
We evaluated the natural killer (NK) cytotoxicity in spleen, thymus and axillary nodes and lymphocyte subsets in peripheral blood.
There was a significant decrease in the NK cytotoxicity in the spleen, in the DEFB12/CONFA group (P<0.05), but neither in the thymus nor the axillary nodes. Furthermore, we observed a significant decrease in the CD45 lymphocyte subsets in the groups DEFB12/CONFA and DEFB12/SUPFA (P<0.05) but not in lymphocyte subsets CD4, CD8, CD3 and CD161.
An imbalance between B12 and FA concentrations during ageing alters some immunological parameters such as the NK citotoxicity and CD45 lymphocyte subsets. These effects have not been observed in a control (CONB12/CONFA) situation or even during deficiency of both vitamins (DEFB12/DEFFA). Therefore, the balance between the intake of folate and vitamin B12 could be as important as their absolute concentrations in the diet.