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Validation Information: FFQ
Validation of a food frequency questionnaire for use in a Scottish population: correlation of antioxidant vitamin intakes with biochemical measures
Background: The food frequency questionnaire (FFQ) has become established as the primary method for assessing dietary intake in epidemiological studies of diet and disease; attention must now be given to developing and evaluating FFQs that extend the range of populations studied.
Aim: To assess the validity of antioxidant vitamin intake estimates derived from a self-administered food frequency questionnaire which was developed for use in Scottish populations.
Method: Intake estimates of vitamins A, C, E and β-carotene were compared with corresponding biochemical measurements in 273 Scottish men and women aged 39-45 years.
Results: The mean ratios of energy intake to calculated basal metabolic rate were 1.40 for men and 1.46 for women suggesting that the intake values derived from the FFQ were not biased towards under-reporting. Significant positive correlation coefficients ranging from 0.14 (for vitamin A) to 0.42 (for vitamin C) were observed between total intake (including diet and supplements) and plasma values. Adjustment for other known determinants of diet and plasma values (i.e. energy intake, body mass index, gender, smoking and plasma lipid levels) improved the correlations for vitamin E and b-carotene. Excluding supplement users generally reduced the correlations suggesting that failure to include supplemental sources may result in misclassification of antioxidant vitamin intake. The food frequency questionnaire assigned 68-89% of subjects correctly into the upper or lower plus adjacent tertiles of plasma vitamin concentration.
Conclusions: These results demonstrate that the food frequency questionnaire is a valid measure of antioxidant vitamin intake.
Total number of nutrients validated: 4
Not all of the nutrients validated in the validation studies are included in the table below, as statistical data was only selected to be displayed for a number of nutrients, this included:
- Saturated Fat
- Mono-unsaturated Fat
- Poly-unsaturated Fat
- Non‐starch polysaccharides(NSP)
- Folic Acid
- Vitamin B12
- Vitamin C
- Fruit & Vegetables
- Urinary Nitrogen
To find information on the other validated nutrients please read the validation study.
- Macronutrients: 0
- Micronutrients: 4
|Comparator||Lifestage||Sex||Nutrient Measured||Mean Difference||Standard Deviation||Correlation Coefficient||Cohen's Kappa Coefficient||Percentage Agreement||Percentage Agreement Categories||Lower Limits of Agreement||Upper Limits of Agreement|
|Biomarkers||Adults||Male Only||Vitamin C (mg)||115.9 (Diary); 40.5umol/L (Biomarkers)||0.42 (P)||89^||3|
|Biomarkers||Adults||Female Only||Vitamin C (mg)||128.2 (Diary); 52.8umol/L (Biomarkers)||0.42 (P)||89^||3|
Some results have been calculated using statistical techniques based on the published data.
For further information on statistical terms click on Statistical tests used in validation studies
All correlations coefficients in the table are unadjusted unless stated otherwise. For adjusted correlation coefficients and other statistical methods used in the study e.g. paired t-tests, please read the validation articles.
- # Adjusted
- † Energy adjusted.
- ‡ For loge-transformed, energy-adjusted nutrient intakes.
- ^ Adjacent included.
- ᵟ Participants provided identical responses.
- (w) = Weighted.
Bodner CH, Soutar A, New SA, Scaife AR, Byres M, Henderson GD, et al. Validation of a food frequency questionnaire for use in a Scottish population: correlation of antioxidant vitamin intakes with biochemical measures. Journal of Human Nutrition and Dietetics. 1998 Oct 1;11(5):373-80.