UNDER- AND OVERREPORTING OF ENERGY INTAKE USING URINARY
CATIONS AS BIOMARKERS: RELATION TO BODY MASS INDEX.
Jianjun Zhang, Elisabeth HM Temme, Satoshi Sasaki and Hugo Kesteloot.
Chair in Nutritional Epidemiology, School of Public Health, Catholic University of
Leuven, Kapucijnenvoer 35, B-3000 Leuven, Belgium.
Liesbeth.Temme@med.kuleuven.be
.
Under- and overreporting of energy intake in relation to body mass index
(BMI, kg/m2) were examined using 24 h urinary sodium and potassium as biomarkers.
Data were obtained from 2,124 men and 1,998 women, aged 25-74 years, participating
in the Belgian Interuniversity Research on Nutrition and Health conducted from 1981
to 1984. The ratios of dietary intake to urinary excretion of sodium and potassium, as
a measure for relative underreporting, were inversely associated with BMI (in men, 
= -0.019 for sodium;  = -0.026 for potassium; in women,  = -0.017 for sodium;  =
-0.019 for potassium; all p < 0.0001), independent of age, smoking, alcohol intake and
education level. Since 77% of dietary potassium is excreted in the urine, subjects with
a ratio, (dietary potassium  0.77)/urinary potassium, < 1 were defined as
underreporters and with a ratio > 1 as overreporters. The percent of underreporters
increased with increasing pooled sex-specific BMI deciles ( = 1.88, p < 0.0001) and
was higher than the percent of overreporters in 13 out of the 20 deciles. At a BMI of
25.4, the percent of under- and overreporters equalizes. In conclusion, the relative
underreporting of cation intake and percent of underreporters increase with increasing
BMI. Under- and overreporting predominate in subjects with a higher and lower BMI,
respectively. Overall, prevalence of underreporting predominates. The approach used
in this study allows to study under- and overreporting of energy intake simultaneously
and objectively at the population level.
Acknowledgement: This study was supported by a grant from the Unilever Chair in
Nutritional Epidemiology.