Depletion/repletion studies to determine folate requirements using folate monoglutamate suggest a requirement of the order of 80–100 μg (170–220 nmol)/day. The total body pool of folate in adults is some 17 μmol (7.5 mg), with a biological half-life of 101 days. This suggests a minimum requirement for replacement of 37 μg (85 nmol)/day. Studies of the urinary excretion of folate metabolites in subjects maintained on folate-free diets suggest that there is catabolism of some 80 μg (170 nmol) of folate/day.
Because of the problems in determining the bio-logical availability of the various folate polyglutamate conjugates found in foods, reference intakes allow a wide margin of safety, and are based on an allowance of 3 μg (6.8 nmol)/kg body weight.