An oral folate absorption test was performed in 100 consecutive patien
ts with Crohn's disease (CD) and 20 healthy individuals to investigate
the frequency of abnormal folate absorption in regard to the site of
the disease and to investigate the possibility of defining a subgroup
of patients requiring parenteral folate supplementation. The described
oral folate absorption test can be performed quickly on an outpatient
basis and is capable of distinguishing patients with altered folate a
bsorption from those with normal folate absorption. In 25 patients, ab
normal folate absorption was detected. 16 patients showed impaired fol
ate absorption as indicated by a marked but insufficient increase in s
erum folate levels after oral folate intake, whereas no increase of th
e serum folate levels was detected in the remaining 9 patients. Abnorm
al folate absorption was not correlated with disease extent or activit
y. In patients with only impaired folate absorption, it might be suffi
cient to increase dietary intake of folates. In the remaining patients
with no measurable increase of serum folate levels after oral folate
intake, i.e. about 10% of all patients with CD, parenteral folate supp
lementation could be considered.