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Validation Information: Medical Research Council-Caerphilly Questionnaire

Bolton-Smith 1991

Antioxidant vitamin intakes assessed using a food-frequency questionnaire: correlation with biochemical status in smokers and non-smokers

The increasing interest in the possible role of antioxidant vitamins in many disease states means that methods of assessing vitamin intakes which are suitable for large-scale investigations are now required. The suitability of the food-frequency questionnaire, which was developed by the Medical Research Council - Cardiff Group, for determining dietary intake of antioxidant vitamins in epidemiological studies was investigated in 196 Scottish men. The validity of the dietary data was assessed by comparison with serum vitamin concentrations, and separate analyses were performed for current smokers and nonsmokers. The results showed that total energy intake and the percentage of energy derived from sugar were higher in smokers, and that both dietary and serum values of vitamin C, β-carotene and vitamin E were lower in smokers than non-smokers. After adjustment for serum lipids, energy intake and body mass index, correlation coefficients between dietary and serum vitamins C and E were similar for smokers (r 0.555 and 0.25 respectively) and non-smokers (r 0.58 and 0.32 respectively). Correlation between dietary and serum carotenes was reduced from 0.28 in non-smokers to 0.09 in smokers and correlations for retinol and total vitamin A were weakly significant only for non-smokers. The food-frequency questionnaire assigned > 70% of subjects correctly into the upper or lower plus adjacent tertiles of serum vitamin values, with the exception of β-carotene and total vitamin A for smokers. Thus, the food-frequency questionnaire appeared to be an adequate tool for assigning individuals into tertiles of serum antioxidant vitamins with the main exception of β-carotene for smokers. Marked differences do occur between the vitamins and between the smoking groups which may reflect reduced accuracy of reporting on the food-frequency questionnaire or differential absorption and metabolism of the vitamins.

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Validation Information

Year of Publication

Tool Information

Dietary Exposure Measured
Full Nutrient, Food Groups
Tool Type
Food Frequency Questionnaire
Timeframe Tool Measures info
Portion Size Measures info
Estimates of quantities consumed were obtained for some items: e.g. number and size of slices of bread per day or amount of milk per day, etc. For other foods a mean portion size, calculated from mean values of intakes from an existing 7-day weighed record from South Wales, was used to derive amounts of foods eaten.
Reporting Method info
Usual; Retrospective
Format info
Supplements Measured
Administration Method info

Study Information

Study Location
Aberdeen and North Glasgow, Scotland
Associated Nutrient Database
McCance & Widdowson's The Composition of Foods, 4th edition
Comparator Validated Against


Sample Size
196 (All), 79 (Smokers), 117 (Non-smokers)
Age of Population

Range: 43-52 years

Mean(SD): 45.8(2.9) years (Smokers); 46(2.8) years (Non-Smokers)

Male Only, Male Only (Smokers), Male Only (Non-smokers)
Other Notable Characteristics
Data split by smokers and non-smokers

Total number of nutrients validated: 7 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: 2
  • Micronutrients: 5
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 Retinol (µg) 69^ 3
Vitamin C (mg) 80^ 3
Biomarkers Adults Male Only (Smokers) Retinol (µg) 171 370.4 0.03 (P) 80^ 3 -569.8 911.8
Vitamin C (mg) 31 19.0 0.45 (P) 83^ 3 -6.9 68.9
Biomarkers Adults Male Only (Non-smokers) Retinol (µg) 87 533.2 0.15 (P) 74^ 3 -979.2 1153.2
Vitamin C (mg) 24.1 28.1 0.56 (P) 87^ 3 -32.2 80.4

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.

Bolton-Smith C, Casey CE, Gey KF, Smith WC, Tunstall-Pedoe H. Antioxidant vitamin intakes assessed using a food-frequency questionnaire: correlation with biochemical status in smokers and non-smokers. British Journal of Nutrition. 1991 May 1;65(03):337-46.