Neural tube defects and herbal medicines containing lead: a possible relationship.

Neural tube defects (NTDs) are the most common cause of potentially preventable congenital malformations in the human fetus. Even with the universal folate supplementation the incidence of NTDs remain higher is developing world than the industrialized countries. We think that lead, a component of many herbal medicines taken during pregnancy for generalized well being of mother and fetus may have a role to play. Lead, a bivalent ion, competes with zinc for crossing into the gut wall and hence slowly decreases the zinc stores in the body and replaces them with lead. As zinc is required at many steps in the absorption and synthesis of biologically active folate moiety, this state of zinc deficiency leads to lack of folate in the metabolically active cells. Hence, the DNA repair and nucleic acid biosynthesis are largely affected in the rapidly dividing embryo leading to NTDs and other abnormalities. We suggest that the marketing of the herbal medicines should be regulated and scientific studies should be carried out on them in order to know their potential effects.