1917 Archives of Internal Medicine  
It is known that there may be a variation of more than 100 per cent. in the blood urea concentration of any group of normal subjects. It is not known why this considerable degree of variation should exist. From the available data it is possible to suppose that each person has his own characteristic blood urea concentration, which varies only within narrow limits, although the variation between different subjects is so large. Or it may be that the blood urea concentration in each person varies
more » ... ach person varies widely in accordance with one or other of the many constantly changing conditions of the body. One cause of variation in the concentration of some constituents of the blood of different persons is a variable food intake. And before any study of the effect of physiologic variables on the blood urea concentration can be carried out or any attempt made to draw any but the broadest line between normal and abnormal, it is necessary to determine the range of variation in subjects in whom this possible cause of variation has been removed by the imposition of a qualita¬ tively and quantitatively constant diet. Yet we do not so much as know whether food alterations can influence the blood urea concen¬ tration in normal subjects. It is only in the most recent work that even inadequate attention has been paid to the possibility of the effect of dietary factors. Bang1 carried out determinations of nonprotein nitrogen, urea nitrogen and amino-acid nitrogen on eight students while they were on a diet which was more or less qualitatively the same, though it is not stated that any quantitative restrictions were imposed. His methods are analogous to his micromethod for sugar estimation in the blood, in that only one or two drops of blood are used. He found a variation of from 0.006 to 0.022 per cent, urea nitrogen before breakfast. He states that under ordinary conditions dietary changes have no effect on the blood urea concentration of normal persons. Schwartz and McGill2 found a variation of from 0.0108 to 0.0156 per cent, urea nitrogen in four normal subjects after
doi:10.1001/archinte.1917.00080230010002 fatcat:4lngdryihrdxforpokyodcvmbq