Direct method of dietary assessment:
Direct methods involve dietary assessment at individual level and can be subdivided into two categories:
- Retrospective method
- Prospective method
Retrospective method:
Retrospective method collect data of food and beverages already consumed. Accuracy of these methods completely rely on the memory-of the respondents that what and how much they have eaten in the past times.
Quantities of food eaten can be assessed by showing pictures and models of foods or with help f standard household measuring unit such as cups and spoons etc.
Diet history;
Diet method is radiationally used to assess a person' s dietary pattern over prolonged period of time such as over a month or year. The method not only collect information on the quantity and frequency of the food being consumed but also their complete preparation methods. Diet history method time was design by Bruke in 1940, which was based on three mandatory steps;
1)Comprehensive interview of the respondent about his usual diet pattern.
2)Food list in the form of questionnaire to ask about quantity consumed of quantity and frequency of a particular food, to make a cross check between verbal and written information
3)A 3-day record with estimates of portion sizes consumed
An expert nutritionist/surveyor start the interview to get information on the general habits including number of meals eaten per day, food supplements , rest, work, exercise and sleep routines, and other daily activities.
This allows the interviewer to choose the appropriate method of interview that can help the respondent in the recalling and providing accurate information.
The interview follows the protocols used in 24 hour dietary recall interviewer inquires the information about the foods eaten during the meals, in between meals and maintained regarding respondent' s eating patterns i.e. type of foods eaten their quantity, frequency and timing a alongside partitions in dietary pattern with changing season.
To cross check, the interviewer than ask the respondent to tell about his/her general food intake habit, for example during the interview if the respondent has said that he took 1 glass of milk in the morning, the interviewer cross checks it by asking his milk intake habits.
At the end, the respondent is asked to complete a 3-day food consumption record that serves as an additional resource to cross check the usual food consumption patterns.
The method designs by Bruke is however, considered impractical because is solely depends upon the training and ability of the interviewer to obtain, enter and code the respondent, s information.
Newer version with slight modifications has been developed and used to assess individual' s usual foods consumptions and eating habits over an extend time period.
The major change made in Bruke' s method was the removal of 3 -day record. Instead of food list questionnaires, several instruments have been developed to obtain information regarding food consumption pattern.
These instrument characterize food in more detail than the food list such as preparation methods of composite dishes etc.
Some instrument record data about the food consumed at each meal. In addition to these instrument some computer based software have also been developed that simplify the data entry either by interviewer or or respondent himself.
However, this can result in high burden on respondents to record diet histories for long duration.
Application of diet history;
1)Mostly use in clinical practices
2)Collect information about usual eating habits
3)Provide information about dietary
4)Useful in the epidemiological studies conducted to identify diet-diseases and diet-relationship
5)Collect data about mean nutrient in take over a specific time period.
b.24-hour recall method:
In 24 hour recall the respondent is asked to recall the foods eaten during last 24 hours or previous day. There are several methods to conduct 24 hour recall including:
- Interview by an expert
- By telephonic communication
- Self-administered record on paper or on computer program
Most common method to start 24 hour recall is to ask the respondent to tell about first food or drink just after awakening the last morning. Some interviewers follow the practice of asking respondents to recall food eaten from midnight to midnight of last day.
Asking about activities done in evening may help respondent in recalling the snacks or drinks he/she might have taking while walking or watching TV.
On completion of interview collected data is cross checked for error or omissions. The respondent may later be contacted by telephone or e-mail. Once complete information is gathered the food and drinks consumed are coded for further analysis.
Application of 24 hour recall:
Suitable for nutritional survey, prospective cohort studies and international studies due to better response rate and case of information gathering.
Useful for studies requiring average food consumption of a specific population.
This method is often used as reference to assess validity of other assessment methods i.e diet history and FFQ'S
c. Food frequency questionnaire FFQ:
Food frequency questionnaire are used to assess the nutrient or energy intake by determining that how frequently a person eat energy rich or nutrient dense food from specific food group.
The questionnaire develop for this purpose contain a list of almost 150 foods from different food groups that are consider major contributor of energy and nutrients a population.
Respondents are asked to indicate how many time they have consumed a particular food in a day, week, month or year. In some FFQ where portion size is not asked it is recommended to use standard portion sizes to measure food consumption per serving.
Mostly they ask how many time in a day, week, month or year a person has eaten bread, cereals, meat, eggs or ice-cream. These types of questionnaires are called non-quantitative or simple FFQ;s.
Little detail about portion sizes is inquired from respondents in semi-quantitative FFQ's. They contain question like how many times in a day, week, month or year person has consumed slices of bread, 1/3 cup of cooked rice, 1 ounce of meat, 1/2 cup of ice-cream.
In addition respondent are asked to mention there usual serving sizes as small, medium, or large in comparison to standard serving sizes. Respondents mark their answer on paper sheet which are optically scan so that, they can be analyzed.
Application of FFQ's:
FFQ's are used on large scale epidemiological studies to evaluate diet-disease relationship.
FFQ's are helpful in assessment of seasonal variations in diet pattern.
FFQ's is a timesaving approach and is easy to handle.
Trained interviewers, having good knowledge about local customs and cultures, will be helpful in obtaining desired information.
Prospective direct methods:
In this all food and beverages consumed are recorded by the person at the time of their consumption, allowing the reporting of current food intake.
a. estimated food records:
Respondents are asked to document all foods, beverages all food along with their portion size over a predefined time period e.g 1 to 7 days. Number of days for keeping food record is decided based on the purpose of assessment or information needed.
If the assessment is to record the average food record , then 1 day food record is sufficient. However, if data is obtain for usual eating habit of individual respondents, then food record of more than1 day will be needed.
b. Weighed food records:
The weighed food record method is consider most accurate method for estimation of individual's food and nutrient intake. This method follows the same principle as of estimated food record. Though the measuring unit in this method are weighing scales such as digital electron weighing scale with tare button.
c. duplicate food collection:
For duplicate collection of method respondents collect the food or beverages identical to what they have eaten in similar containers in which they had consumed.
The containers are as such then sent to chemical laboratories for exact quantification of nutrients. To prevent from contamination, duplicate food containers should be kept in refrigerator until delivery to laboratories daily.
what are the direct method of nutritional assessment?
what are dietary method of assessment?
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