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Validation Information: FFQ

Bodner 1998

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.

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Validation Information

Year of Publication

Tool Information

Dietary Exposure Measured
Tool Type
Food Frequency Questionnaire
Timeframe Tool Measures info
1 Year
Portion Size Measures info
Standard portion sizes.
Reporting Method info
Usual; Retrospective
Format info
Supplements Measured
Administration Method info

Study Information

Study Location
Grampian region, Scotland
Associated Nutrient Database
McCance & Widdowson's The Composition of Foods, 5th edition
Comparator Validated Against


Sample Size
118 (Male), 155 (Female)
Age of Population

Range: 39-45 years

Male Only, Female Only
Other Notable Characteristics
Participants were part of a trial looking at antioxidant intake and adult onset asthma.

Total number of nutrients validated: 4 info

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:

  • Energy
  • Fat
  • Saturated Fat
  • Mono-unsaturated Fat
  • Poly-unsaturated Fat
  • Carbohydrates
  • Protein
  • Sugar
  • Non‐starch polysaccharides(NSP)
  • Sodium
  • Calcium
  • Iron
  • Zinc
  • Retinol
  • Folate
  • 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 info Mean Difference Standard Deviation info Correlation Coefficient info Cohen's Kappa Coefficient Percentage Agreement Percentage Agreement Categories info 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.