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Validation Information: myfood24

Wark 2018

Validity of an online 24-h recall tool (myfood24) for dietary assessment in population studies: comparison with biomarkers and standard interviews

Background: Online dietary assessment tools can reduce administrative costs and facilitate repeated dietary assessment during follow-up in large-scale studies. However, information on bias due to measurement error of such tools is limited. We developed an online 24-h recall (myfood24) and compared its performance with a traditional interviewer-administered multiple-pass 24-h recall, assessing both against biomarkers.

Methods: Metabolically stable adults were recruited and completed the new online dietary recall, an interviewer-based multiple pass recall and a suite of reference measures. Longer-term dietary intake was estimated from up to 3 x 24-h recalls taken 2 weeks apart. Estimated intakes of protein, potassium and sodium were compared with urinary biomarker concentrations. Estimated total sugar intake was compared with a predictive biomarker and estimated energy intake compared with energy expenditure measured by accelerometry and calorimetry. Nutrient intakes were also compared to those derived from an interviewer-administered multiple-pass 24-h recall.

Results: Biomarker samples were received from 212 participants on at least one occasion. Both self-reported dietary assessment tools led to attenuation compared to biomarkers. The online tools resulted in attenuation factors of around 0.2-0.3 and partial correlation coefficients, reflecting ranking intakes, of approximately 0.3-0.4. This was broadly similar to the more administratively burdensome interviewer-based tool. Other nutrient estimates derived from myfood24 were around 10-20% lower than those from the interviewer-based tool, with wide limits of agreement. Intraclass correlation coefficients were approximately 0.4-0.5, indicating consistent moderate agreement.

Conclusions: Our findings show that, whilst results from both measures of self-reported diet are attenuated compared to biomarker measures, the myfood24 online 24-h recall is comparable to the more time-consuming and costly interviewer-based 24-h recall across a range of measures.

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Validation Information

Year of Publication

Tool Information

Dietary Exposure Measured
Energy, Macronutrient, Micronutrient, Food Groups
Tool Type
24 Hour Recall
Timeframe Tool Measures info
1 Day
Portion Size Measures info
Portion images, standard pack sizes and a section where particpants can enter their own amount.
Reporting Method info
Retrospective; Prospective
Format info
Supplements Measured
Administration Method info
Self-administered or Interviewer-administered

Study Information

Study Location
Leeds, England
Associated Nutrient Database
UK food database
Comparator Validated Against
24hr Recall, Biomarkers


Sample Size
212 (Adults)
Age of Population

Range: 18-65 years

Mean(SD): 43(15) years (Male); 44(16) years (Female)

Other Notable Characteristics
Online tool compared to biomarkers and 3 x 24h recalls

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.

  • Energy
  • Macronutrients: 9
  • Micronutrients: 8
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
24hr Recall Adults Both Energy (kcal) -10 (Ratio of Geo) 0.51 (ICC) -63 (Ratio of Geo) 118 (Ratio of Geo)
Energy (kJ) -10 (Ratio of Geo) 0.51 (ICC) -63 (Ratio of Geo) 118 (Ratio of Geo)
Protein (g) -9 (Ratio of Geo) 0.45 (ICC) -68 (Ratio of Geo) 158 (Ratio of Geo)
Fat (g) -14 (Ratio of Geo) 0.42 (ICC) -74 (Ratio of Geo) 182 (Ratio of Geo)
Saturated Fat (g) -13 (Ratio of Geo) 0.40 (ICC) -79 (Ratio of Geo) 263 (Ratio of Geo)
MUFA (g) -14 (Ratio of Geo) 0.40 (ICC) -78 (Ratio of Geo) 238 (Ratio of Geo)
PUFA(g) -11 (Ratio of Geo) 0.39 (ICC) -80 (Ratio of Geo) 303 (Ratio of Geo)
Carbohydrates (g) -12 (Ratio of Geo) 0.54 (ICC) -70 (Ratio of Geo) 162 (Ratio of Geo)
Sugars (g) -20 (Ratio of Geo) 0.46 (ICC) -80 (Ratio of Geo) 216 (Ratio of Geo)
Fiber (g) -14 (Ratio of Geo) 0.43 (ICC) -75 (Ratio of Geo) 199 (Ratio of Geo)
Sodium (mg) -4 (Ratio of Geo) 0.44 (ICC) -76 (Ratio of Geo) 283 (Ratio of Geo)
Calcium (mg) -7 (Ratio of Geo) 0.46 (ICC) -79 (Ratio of Geo) 223 (Ratio of Geo)
Iron (mg) -10 (Ratio of Geo) 0.46 (ICC) -70 (Ratio of Geo) 170 (Ratio of Geo)
Zinc (mg) -10 (Ratio of Geo) 0.46 (ICC) -72 (Ratio of Geo) 197 (Ratio of Geo)
Retinol (µg) -27 (Ratio of Geo) 0.37 (ICC) -98 (Ratio of Geo) 2188 (Ratio of Geo)
Folate (µg) -14 (Ratio of Geo) 0.45 (ICC) -78 (Ratio of Geo) 215 (Ratio of Geo)
Vitamin B12 (µg) -27 (Ratio of Geo) 0.40 (ICC) -90 (Ratio of Geo) 422 (Ratio of Geo)
Vitamin C (mg) -28 (Ratio of Geo) 0.45 (ICC) -94 (Ratio of Geo) 765 (Ratio of Geo)

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.

Wark PA, Hardie LJ, Frost GS, Alwan NA, Carter M, Elliott P, et al. Validity of an online 24-h recall tool (myfood24) for dietary assessment in population studies: comparison with biomarkers and standard interviews. BMC Med. 2018;16(1):136.