Serum retinol distributions in residents of the United States: third National Health and Nutrition Examination Survey, 1988-1994.

BACKGROUND: Inadequate vitamin A status has been a potential nutritional problem for some segments of the US population, particularly children and the poor.
OBJECTIVE: We evaluated serum retinol concentration by using population-representative data from 16058 participants aged 4 to >/=90 y in the third National Health and Nutrition Examination Survey, 1988-1994.
DESIGN: We used multivariate regression to examine the simultaneous associations of sociodemographic, biologic, and behavioral factors with serum retinol concentration.
RESULTS: In children, serum retinol concentrations were greater with greater age, body mass index, serum lipids, and the use of supplements containing vitamin A. In adults, male sex, serum lipids, alcohol consumption, and age were positively associated with serum retinol concentration in most racial/ethnic strata. Household income was not associated with serum retinol concentration in children; associations were inconsistent in adults. The prevalence of serum retinol <0.70 micromol/L was very low in all strata; the prevalence of serum retinol <1.05 micromol/L was 16.7-33.9% in children aged 4-8 y and 3.6-14.2% in children aged 9-13 y, depending on sex and racial/ethnic group. The prevalence of serum retinol<1.05 micromol/L was higher in non-Hispanic black and Mexican American children than in non-Hispanic white children; these differences remained significant (P < 0.0001) after covariates were controlled for. Among adults, nonwhite women were significantly (P < 0.0001) more likely than white women to have serum retinol <1.05 micromol/L after covariates were controlled for.
CONCLUSIONS: Clinically low serum retinol concentration is uncommon in US residents aged > or = 4 y, although racial/ethnic and socioeconomic differences in serum retinol concentration still exist.