Hourly variation in total serum cholesterol.

D URING A STUDY" 2 of variations in serum cholesterol, we observed striking changes from day to day in certain subjects. In a few individuals the change in serum cholesterol was more than 200 mg. per cent from one morning to the next. In sharp contrast , in other subjects the level of serum cholesterol seemed quite stable. Similar observations have been made by Thomas and Eisenberg.3 The tendency toward a labile pattern seemed to persist from one year to the next in certain subjects and it therefore seemed desirable to investigate further the rapidity with which changes might occur. Method and Material The studies reported here concern hourly variations in total serum cholesterol among individuals in 2 groups of apparently healthy medical students. Group 1 consisted of 5 students who were selected because of a marked lability in serum cholesterol that each had shown during a previous period of observation. These 5 subjects are referred to later as the "labile group." Group 2 consisted of 5 other subjects whose serum cholesterol had seemed quite stable during the previous period of observation. All subjects in each group had participated in earlier studies in which serum cholesterol had been measured before and during the course of semester examinations. At least 12 determinations of serum cholesterol had been made on each subject and these were scattered over the freshman and sophomore years of medicine. Plan of Study During Christmas holidays the 5 students constituting the "labile group" were hospitalized from December 29, 1958, until January 2, 1959, to facilitate observation. They were ambulatory with certain limitations imposed by the procedure and were fed a general hospital diet of approximately 2,400 calories. Lacto-ovo-vegetarian food sources were used, and the diet was planned to include 75 Gm. of protein, 100 Gm. of fat, and 300 Gm. of carbohydrate. The participants were told briefly of the general plan to be followed in the study. Polyethylene catheters were placed in a brachial vein and blood samples were collected at hourly intervals from 6 a.m. until 10 p.m. and again at 2 a.m. Between samplings a slow infusion of phy-siologic salt solution was maintained to prevent clotting of blood within the catheter. The amount of the infusion varied a little from day to day and among the subjects, but averaged 2,400 ml. for each 24 hours. Subsequent treatment of the 2 groups was as nearly alike as …