Comparison of micronutrient intake measured by a dietary questionnaire and biochemical indicators of micronutrient status.

We compared the intake of 12 micronutrients as reported on a semiquantitative food frequency questionnaire with corresponding biochemical indicators of nutrient status in a sample of 57 males and 82 females aged 40-83 y. Age-, sex-and energy-adjusted correlation coefficients ranged from near zero for thiamin, vitamin A, and zinc to 0.63 for folate. Correlation coefficients between intake and the biochemical measures were > 0.30 for carotenoids, vitamin D, vitamin E, vitamin B-12, folate, and vitamin C. Differences of 50% or more were observed between extreme quartiles of intake for mean plasma concentrations of folate, vitamin B-12, and vitamin C. Excluding nutrient supplement users generally reduced the correlations. These data demonstrate that food frequency questionnaires can provide valid information on intake for a number of micronutrients.