The role of dietary iron in pigment gallstone formation.

Recent studies suggest that dietary factors may be responsible for the increasing incidence of pigment gallstones. Although iron deficiency alters the activities of several hepatic enzymes, its effects on biliary lipid metabolism are not known. The aim of this study was to define the role of dietary iron in pigment gallstone formation. Three groups of prairie dogs were maintained for 2 months on either a control chow (iron-198 ppm), a high-carbohydrate diet with normal iron levels (CHO group; iron-220 ppm), or a high-carbohydrate, iron-deficient (iron-56 ppm) diet (CHO-FeD group). Serum analysis confirmed iron deficiency in the CHO-FeD group. The CHO animals had a significant (p less than 0.01) increase in hepatic bile phospholipids, while CHO-FeD animals had increased (p less than 0.01) concentrations of phospholipids and cholesterol as compared with controls. Similar findings were noted in gallbladder bile with the addition of increased calcium levels in both carbohydrate groups. Calcium bilirubinate crystals and stones were found in only 17% of CHO animals, as compared with 67% of CHO-FeD animals. These data indicate that consumption of diets rich in carbohydrates but deficient in iron alters hepatic metabolism of cholesterol and may be an important etiologic factor in pigment gallstone formation. Iron supplementation may prevent pigment gallstones in certain high-risk groups.