Longitudinal measurements of blood volume and essential body mass in human subjects

Repeated determinations of blood volume and body density were made on 34 Chinese subjects (28 men and 6 women) in Taiwan over a period of 12 yr, as the mean age increased from 31 to 43 yr. Essential body mass calculated from body density and body weight showed no significant change over the 12-yr period. Changes in body weight (mean gain equals 6.0 kg) were attributable to alterations in adipose tissue weight, the density of which was found to be 0.948 g/cm3. In two-thirds of the subjects the second blood volume increased by more than 5% over the first determination, and the mean blood volume for all subjects increased by 7.5% (P less than 0.01). Correlation of the blood volume data with the findings on essential body mass and adipose tissue mass suggests that blood content per unit tissue mass increased in the second determination. This interpretation is supported by the increase in nutrient availability in Taiwan over the 12-yr period, and it may explain the lack of blood volume increase in an earlier longitudinal study on American subjects with stable nutrient availability.