The protective role of folate in preventing neural tube defects is now well
established. The hypothesis is advanced here that photolysis of folate by
ultraviolet (UV) light may, in some women, precipitate a folate deficiency
sufficient to cause a neural tube defect (NTD) during the first few weeks o
f pregnancy. This hypothesis is supported by the demonstration of in vitro
photolysis of folate by simulated strong sunlight (1), a decline in folate
levels in light-skinned subjects exposed to UV light for dermatological con
ditions (1), and the occurrence of NTDs in the offspring of women who expos
ed themselves to high levels of UV light on the sunbeds of tanning salons (
2). If established, a connection between in vivo folate photolysis by UV li
ght, clinical folate deficiency and NTDs would suggest that intense or prol
onged periconceptual exposure of women to UV light for recreational or ther
apeutic reasons should be avoided.