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Interviewer-led recalls vs myfood24: time and cost in large-scale research studies

Have you ever realised how long it takes to conduct interview-led recalls, manually coding food diaries for each participant and the financial costs of it all? We break down the process to show you how using myfood24 instead can save you time, effort, and money for accurate results in a large-scale epidemiological study.

When it comes to conducting research, the importance of obtaining accurate and reliable results can’t be disputed.

But, ensuring your data is appropriately gathered using robust methods can be hard to achieve, particularly when it comes to measuring diet and nutritional intake.

Interview-led recalls are a common method of choice due to the useful detailed accounts of individual food consumption. Though it can lead to accurate results, it comes at a cost.

Not only can interviewer-led recalls be subject to possible bias and misreporting, but the process is also particularly time-consuming, and the financial costs can be considerably high. As a researcher, you’ve got to consider:

  • The cost of hiring trained interviewers
  • The time it takes to conduct lengthy interviews to report all foods consumed by an induvial
  • The relevant biases that can be introduced using this dietary assessment method
  • The time it takes to manually code food diaries:
    • Identifying the appropriate foods from standard food composition tables
    • Quantify the portion size of each food item
    • Calculate the overall food and nutrient intake
    • It may also require a trained nutritionist which comes at an additional cost

Imagine conducting these activities for a large-scale study of maybe 100 to 1000 participants, or even more.

The process to interview and obtain the results from every individual greatly increases in time, and money.

Compared with myfood24, interviewer-led recalls are more expensive and lengthier, but evidence shows that they are both just as accurate when obtaining food and nutrient data in large-scale studies.

Using online nutritional analysis software instead of interview-administered recalls can significantly decrease the concerns of time and money without compromising on accurate results.

To demonstrate, let’s break down the traditional interviewer-administered 24-hour recall, coding process, and its cost, compared with the online tool.

How long does it take to conduct an interview-led recall?

Interviewer-led recalls can take a substantial amount of time, especially when there is a high number of participants involved.

The higher the sample size, the longer the interview process is going to take to gain the required daily intake information.

Often, 24-hour recalls are conducted on multiple days and, depending on the length and nature of the study, multiple recalls can be carried out at different time points and so additional interviews are needed.

As an example, if a study’s purpose is to monitor habitual intake over one year, it’s likely that seasonal recalls will be conducted to account for seasonal variation, increasing the number of 24-hour recalls and therefore interviews.

Interviews tend to be completed face-to-face or by other means, including telephone interviews, and the length of time the interview process can take differentiates depending on what information is required, participant numbers and participant availability.

When interviews are conducted, one interview can last between 20 to 60 minutes to complete per individual, but this can increase depending on the variety of foods and additional details required.

This time quickly adds up particularly in large-scale studies, of over 300 participants.

Say it takes 45 minutes, on average, to complete one interview per individual:

For 1 participant:

24hr recall x 1 day = 45 min

24hr recall x 3 days = 135 min

24hr recall x 3 days x 2 different timepoints = 270 min

For 300 participants:

24hr recall x 1 day = 13,500 min (225 hours, equivalent to 9 days)

24hr recall x 3 days = 40,500 min (675 hours, equivalent to 28 days)

24hr recall x 3 days x 2 different timepoints = 81,000 min (1,350 hours, equivalent to 56 days)

The time to conduct interviews adds up massively, especially when more 24-hour recalls need to be performed and at different time points.

But in addition to the length of time the interviewing process can take, it may be difficult to even arrange interviews with participants to start recording their dietary intake to account for food consumption from the previous day.

This can be due to the respondent’s availability to conduct face-to-face or phone interviews, but it can also come down to whether a trained interviewer is available to conduct the assessment – which comes at a financial cost.

How much does it cost to hire a trained interviewer?

An interviewer-administered 24-hour recall can be expensive to conduct.

A trained interviewer is typically hired to ensure more accurate accounts of food intake are recorded, and appropriate questions and prompts are used to gauge as much detailed daily intake as possible.

The interviewer may be employed by the hour, ranging between £7 to £10 per hour on average, or hired on a fixed-term or permanent basis which may cost around £29,000, based on the average cost of a Research Assistant for example.

This may be quite an expensive annual output depending on how long a study can last.

If we follow on from the previous example of the time it takes to conduct 300 interviews for one 24-hour recall, which can take 225 hours, hiring a professional interviewer at around £8.50 an hour (as an overall average) is going to cost £1,912.50.

As we know, multiple interviewer-led recalls are required for large-scale studies and so the sum significantly increases:

Number of 24-hour recalls The time it takes (avg. hrs) Cost to hire (at £8.50p/h)
1 225 £1,912.50
2 450 £3,400
3 675 £5,737.50
4 900 £7,650

And when recalls need to be conducted at multiple time points, the price will keep on rising.

It’s clear that it can get quite expensive to hire well-trained interviewers, but they are needed to minimise recall bias to obtain reliable results.

It is important to note that the entire interviewing process and results gathered don’t account for coding food items into a diary.

The coding process and analysis of the data obtained must be manually completed by a trained nutritionist or professional.

How long does it take to code a diary?

Similarly to the interview process, data processing is quite an intensive and time-consuming activity, especially as it needs to be completed before the next 24-hour recall.

Trained nutritionist coding a food diary after food intake diaries have been gathered from interview-led recalls

When identifying food items and analysing their nutritional composition, every food and drink item recorded from each recall must be manually coded into analysis software, using food composition databases to calculate the corresponding nutritional information.

With this, there can be several recording errors and variation in interpretation within manual data processing.

Many items will need to be examined to identify outliers, some coded items will need to be reviewed to ensure the accuracy of portion sizes are correct and the database needs to be kept up to date to ensure nutritional compositions of foods are accurate.

With some entries, it’s up to the coder to assume and estimate the correct nutritional properties if not available, which has a chance of being incorrect and impact accuracy.

When it comes to the amount of time it takes to code all this information, it can be lengthy, especially with multiple diary data from 300 participants.

On average, it takes about 45 minutes to one hour to code a 4-day diary from one participant, meaning for 300 respondents it could take between 225 and 300 hours, equivalent to 9 and 12.5 days, to code the entire cohorts intake.

If a trained nutritionist were hired to do this, the financial cost would also significantly rise.

Trained nutritionists tend to be salaried between £24,907 and £37,890, depending on experience. For a well-experienced nutritionist to code dietary data accurately, the cost would reach around £31,398, adding another annual expense notably when combined with the costs of hiring a trained interviewer.

What is the overall expense of interviewer-led recalls?

It’s clear that the interview-led recalls and coding process is both timely and costly.

To highlight by how much, we can take our sample size example of 300 participants combined with the time and costs we’ve worked out to demonstrate the expense of an interview-led recall:

Conducting one large-scale study of 300 participants with three 24-hour recalls at two different time points, with hire costs of a trained interviewer and nutritionist, the overall cost would amount to:

  • 1,500 hours or 62 days in the time it takes to conduct interviews and code data
  • Between £42,873 – £60,049 in financial costs:
    • £11,475 in hiring costs for a trained interviewer, or the contracted RA wage (£28,651)
    • £31,398 on top for a trained nutritionist to code data

Imagine this in a bigger study, with more recalls, possibly more than one interviewer and nutritionist, and over a longer period of time – the costs soon add up at an exponential rate.

Interviewer-led recalls may be beneficial in terms of detailed information, but there are many limitations to its process. From interviewer bias, time constraints, coding errors and financial burdens, the method faces many obstacles to obtain accurate dietary and nutrient intake data which can negatively impact the validity of large-scale epidemiology studies.

The introduction of automated dietary analysis software, such as myfood24, can be used as an alternative method to collect accurate results quickly and easily, with less financial constraints.

Using myfood24 to replace interviewer-led recalls

myfood24 is an online 24-hour dietary assessment tool, aiming to take away the burden of traditional interviewer-administered recalls.

As a self-completed and automated online nutritional analysis software, myfood24 enhances the speed it takes to collect and process information, and at a reduced cost.



The self-completed system is a quicker and easier way to collect accurate dietary intake at a time and location that is convenient for the study participant, saving you time and money hiring a trained specialist to conduct the interview.

Participants enter their daily intake using an online food diary, with the ability to select from a vast range (over 62,000) of generic and branded food and drink items to reflect the wide range of products available to consumers, helping for a more accurate recall.

To assist with estimating portion size and potentially missed items, the system contains helpful portion size images and prompts for foods that are commonly consumed together, so there’s less room for memory and misreporting errors.

Automatically generates nutrient intake

As a self-administered system, myfood24 instantly analyses the food diaries and calculates the corresponding nutrition information using our unique food composition databases, without the need to code elsewhere.

The system eliminates the need for manually entering, analysing, and calculating nutrition composition results, and myfood24 also generates downloadable outputs automatically to display the intake of energy and over 100 micro- and macro-nutrients, including vitamins, minerals, and fatty acids.

Since its introduction, the online tool has been developed for research use on an international scale to accurately reflect nutritional intake from a wide range of countries. myfood24 has multiple internationally tailored solutions to measure dietary intake effectively as each version has a localised food composition database.

Evidence shows that myfood24 is just as accurate as interview-led recalls, and the benefit of the whole system is that it’s a more efficient way of measuring short or longer-term dietary intake – and it comes at a reduced financial cost.

Reduced financial cost

If we compare the cost of interviewer-led recalls using our previous example of 300 participants, to the cost of using myfood24’s system, the savings are quite substantial.

To conduct one large-scale study of 300 participants with three 24-hour recalls at two different time points would cost:

myfood24 Interviewer-led
£2,800 (+VAT) £42,873 – £60,049

In this example, you can save up to £57,249 by using myfood24 instead of interviewer-led recalls.

The dietary assessment tool is nothing short of low expense when compared with the combined costs of hiring trained researchers and the time it takes to collect and process information.

Time to use an alternate method

When we compare the two types of dietary assessment methods, the benefits of nutritional analysis software far outweigh the advantages of interviewer-led recalls.

myfood24 self-administration saves time and effort by removing the need to conduct interviews and code data using a multitude of food composition tables, and quite importantly, it saves money by eliminating the financial costs of hiring trained professionals.

There is less room for human and systematic errors, and the evidence shows that myfood24 performs just as accurately as interviewer-led recalls.

As a result, using myfood24 for 24-hour recalls in large-scale epidemiological studies is an easy decision to make.

If you’re interested in finding out more about myfood24 for research, click here

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