Comparative Merits of Fasting Specimens, Random Specimens and Oral Loading Tests in Field Nutritional Surveys

1Repetition of 4-hour oral vitamin loading tests employing ascorbic acid, thiamine, riboflavin and nicotinamide administered at intervals of 2 or 3 weeks to soldiers subsisting on good field rations had no significant effects on the results of subsequent loading tests or on the fasting urinary excretion of ascorbic acid, thiamine, riboflavin or N1-methylnicotinamide.2Under the same circumstances the fasting rates of urinary excretion of ascorbic acid, thiamine, riboflavin and N1-methylnicotinamide were more sensitive measures of vitamin intake in the previous 3 weeks than were 4-hour oral vitamin loading tests.3Whole blood hemoglobin serum protein, serum chloride and serum ascorbic acid varied relatively little in the course of the day.4In contrast to the results for blood and serum, the fasting urinary rates of excretion of chloride, ascorbic acid, thiamine, N1-methylnicotinamide and riboflavin and values obtained at other times of day were not satisfactorily related in a simple manner either when expressed: (a) as concentration per 100 ml. of urine, (b) as concentration per 100 ml. of urine corrected to specific gravity 1.010, or (c) as excretion per hour.5The practical conclusions for nutritional surveys are that when it is not possible to conduct all the tests that might be desired, fasting levels should be determined in preference to the results of loading tests; that specimens of blood may with reservations be drawn at any time of day; and that random specimens of postprandial urine should be avoided if possible. These conclusions are limited to hemoglobin, serum protein, chloride and ascorbic acid; and to urinary chloride, ascorbic acid, thiamine, N1-methylnicotinamide and riboflavin.