Association of food frequency questionnaire estimates of vitamin A intake with serum vitamin A levels.

To assess the validity of nutrient intake estimates from a food frequency questionnaire, the authors compared estimates of intake of preformed retinol (dietary plus supplements), beta-carotene, other active carotenoids, and total vitamin A computed from questionnaire responses with serum retinoid and carotenoid concentrations. Data were obtained from 302 male and female current or former smokers, participants in a lung cancer chemoprevention trial at the Fred Hutchinson Cancer Research Center in Seattle, Washington, during 1985-1986. Both serum beta-carotene and serum alpha-carotene were associated, although weakly, with food frequency estimates of total vitamin A intake, dietary vitamin A, beta-carotene, other carotenoids, and total carotenoids (0.18 less than or equal to r less than or equal to 0.26). Serum retinol was associated with supplementary vitamin A intake (r = 0.16). Nondietary factors were also associated with serum nutrient concentrations--in particular, cigarette smoking, alcohol intake, and body mass index. Cigarette smoking emerged as an important modifying factor of the relation between serum beta-carotene and dietary beta-carotene (r = 0.14 for current smokers, r = 0.30 for former smokers).