Does aging affect the intestinal transport of 5-methyltetrahydrofolate?

Aging is associated with increased incidence of folate deficiency. The mechanism responsible for the deficiency is not known but could include a decrease in the intestinal absorptive capacity for folates. Therefore, we examined the intestinal absorptive capacity for folate in young and old rats. We assessed the absorption of the natural folate derivative, 5-methyltetrahydrofolate in 3- and 25-month-old rats, using jejunal everted sacs. The kinetic parameters of 5-methyltetrahydrofolate absorption disclosed apparent Kt of 7.7 and 6.54 microM and Vmax of 0.96 and 1.14 nmol/g initial tissue wet weight/30 min in young and old rats, respectively. These data do not demonstrate an aging-associated decrease in the intestinal transport capacity for 5-methyltetrahydrofolate. Therefore the deficiency of folate found in the elderly is unlikely to be due to intestinal malabsorption of folate monoglutamates. Other mechanisms must play a role in the deficiency of folate seen in the elderly.