Dietary intake assessment - Food diary

food diary image

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Population of Interest (P=Parent, R=Researcher, C=Child)

  • Age: <1 yr (P); 1-10 yrs (P); 3-5 yrs (P); 10-12 yrs (P and/or C); 12 yrs+ (C)
  • Setting: Clinical; Home; Community; Population
  • Administration Method: Self Report


Written records of actual intake of foods and beverages consumed at the time of consumption for a specified period (usually 3, 5, 7 days). Food can be measured using weights or estimated using standard household measures (eg. cups, tablespoons), food models and pictures.


Under-reporting of energy intake may increase with age. Possible differences between children of different ethnic backgrounds.

When to use

For estimating group means: A single record is sufficient. All days of the week should be equally represented, or at least weekdays and weekend days, due to systematic difference between days of the week.

For estimating the distribution of individual intakes within a group or for obtaining usual individual intake: Multiple records need to be collected eg. to determine the proportion of individuals at risk of inadequate intake of a particular nutrient or to predict individual outcomes such as serum cholesterol. The number of days depends on the day-to-day variation of intake of the nutrient of interest and the level of precision desired. For energy and the macronutrients, 3-10 days has been suggested. For other nutrients, up to 50 days may be required. Four to 5 days are often selected as a reasonable compromise for assessing energy & the macronutrients. If an estimate of long-term intake is required, 3-4 days in each of the four seasons of the year is ideal (ie. 12-16 days in total).


Alterations to food intake as with any prospective method.
Diet records, either weighed or estimated, have been shown to provide unbiased records of energy intake in lean subjects up to 9 years old. However, adolescents under-report energy intake by this method by approximately 20% with the greatest bias observed in older subjects.

The validity of records or recalls for measuring long-term or usual food intake improves with more days of recording, indicating multiple records may be needed. Multiple records/recalls can introduce compliance issues for children because of the high respondent burden.


High participant and researcher burden. This is depedent on the number of days a diet has to be recorded and the record is to be entered and analysed.

Considerations (miscellaneous)

If multiple days are collected, days should be randomized to cover weekday and seasonal variation. The reporting must be done at the time of consumption on paper or using a dictaphone. Higher respondent burden for multiple days may result in lower cooperation and data quality.

Food records require children to write names of foods legibly, recognise and describe quantities, decipher food label information and retain the record in their possession for completion of all entries during the day.

In most validation studies carried out in children that have employed weighed or estimated diet records, they have been shown to provide unbiased records of energy intake in LEAN subjects to age 9, however in older children food records unanimously underreport by 20% with greater bias in older children.


Current diet, direct observation of what is eaten, duration of survey can be varied to meet requirements for precision of estimates of food consumption or nutrient intake. Widely used, facilitates comparisons between studies, precision of portion sizes. Often regarded as the ‘gold standard’ among dietary assessment methods. Does not rely on respondents’ memory. Open-ended.


Labour-intensive for both the researchers and participants, requires literacy and numeracy skills, subjects need to be well motivated, usual consumption pattern may change due to – inconvenience of recording, choice of foods which are easy to record, beliefs about which foods are healthy or unhealthy. Overweight subjects tend to under-report true consumption levels. Coding and data entry errors common. Food composition tables used to estimate nutrient intake.
Unrepresentative of usual intake if only a few days assessed.
Inappropriate for assessment of past diet.
Collection of multiple days of intake is not feasible for most epidemiologic studies.
Respondents need to be motivated and literate. Habitual eating patterns may change due to the recording process. Reliability of records decreases over time because of respondent fatigue.

How long do you need to get participants to keep the records for?

Much research has addressed how to calculate the number of days required to estimate intakes of individuals nutrients for children aged 2-17 years.

7 day dietary diaries have been shown to give unbiased estimates of energy intake in normal weight children between 4-10 years, but an underreporting by 20% has been shown when using this method to older children and adolescents. 7 days of food records for children <4 are inadequate because time period is too short.

A 3 day record is long enough to gain insight into regular food intake without being to labour intensive for caregivers or invasive for toddlers, but is still sufficient to determine differences in nutrient intake between groups and comparison with RDI’s.