Lack of effect of experimental ascorbic acid deficiency on bile acid metabolism, sterol balance, and biliary lipid composition in man.

Abstract

Extensive studies in animal models indicate that subclinical ascorbic acid deficiency impairs the conversion of cholesterol to bile acid, elevates plasma cholesterol levels, and predisposes to development of cholesterol cholelithiasis. The present study was designed to see if this is also true in man. Five normal volunteers were hospitalized in a metabolic ward and placed on a controlled diet containing 3-4 mg of ascorbic acid each day. Ascorbic acid supplementation was given as follows: control period I (days 1-33), 75 mg/day; deficient period (days 34-96), 0 mg/day; and repletion period (days 97-101), 1000 mg/day. In addition, three of the subjects were studied during a second control period (days 102-139) during which they were given 75 mg/day of ascorbic acid. Ascorbate levels at the end of both control periods were 0.87-1.34 mg/dl in plasma and 19.4-29.5 micrograms/10(8) cells in leukocytes. At the end of the deficient period these levels were 0.09-0.15 mg/dl in plasma and 6.2-10.0 micrograms/10(8) cells in leukocytes, levels approaching those seen in scurvy. There was no effect of ascorbic acid deficiency on plasma cholesterol and triglycerides; plasma cholesterol in high, very low, and low density lipoprotein fractions; biliary lipid composition and saturation index of gallbladder bile; synthesis, fractional turnover, or pool size of either cholic or chenodeoxycholic acids; output of fecal acid or neutral sterols; and fecal sterol balance. Total bile acid pool size calculated by the one-sample technique was reduced 11% in the deficient period compared to control period I (P less than 0.005), and increased to 98.7% of the baseline levels in control period II. However, total bile acid pool calculated by the Lindstedt method did not change during deficiency. These data demonstrate that short-term subclinical ascorbic acid deficiency near the scorbutic range has no significant effect on bile acid and cholesterol metabolism in man.