Validity of a self-administered food frequency questionnaire used in the 5-year follow-up survey of the JPHC Study Cohort I to assess carotenoids and vitamin C intake: comparison with dietary records and blood level.

We compared carotene and vitamin C intake assessed with our 138-item food frequency questionnaire (FFQ) against 28-day weighed dietary records among a subgroup of JPHC Study Cohort I (102 men and 113 women), and the corresponding serum carotenoid levels or plasma vitamin C levels (86 men and 100 women). Correlation coefficients between carotenoids or vitamin C intake estimated from FFQ and intakes estimated from DR were as follows in men and women, respectively: alpha-carotene, r=0.47 and r=0.46; beta-carotene, r=0.40 and r=0.30; lycopene, r=0.18 and r=0.22; vitamin C, r=0.44 and r=0.31. Correlation coefficients between carotenoids or vitamin C intake estimated from FFQ and the corresponding serum carotenoids levels or plasma vitamin C levels were as follows: alpha-carotene, r=0.38 and r=0.30; beta-carotene, r=0.28 and r=0.11; lycopene, r=0.30 and r=0.19; vitamin C, r=-0.07 and r=0.06; in men and women, respectively. These data indicated carotenoid and vitamin C intakes estimated from FFQ were associated with intake from DR, although the association was weak for lycopene. Carotenoid intake estimated from FFQ were associated with corresponding serum carotenoid levels in men, but the correlation was weak in women except for alpha-carotene. Both in men and women, no association was observed for plasma vitamin C levels.