The dietary assessment methods can be categorized as either direct or indirect methods. The indirect methods utilize secondary sources of information such as food expenses and food supply to estimate food availability for large populations. Tools involve food balance sheets for data collection at national levels and household consumption and expenditure surveys for data collection at household levels. On the other hand, direct methods involve data gathering from primary sources. In this post we will focus on the direct methods.
Direct dietary methods can be classified as either prospective, retrospective or innovative. The retrospective methods require that one recalls the particular foods consumed within a set period and they include:
24 -hour recall– With this method, you as the participant will be asked questions by a nutrition professional to identify and report all that was consumed during the previous 24 hours-all foods and beverages. You will be required to state any food item ingested within last 24 hours to determine actual nutrient intake. For better precision, several of these non-consecutive 24 -hour recalls can be obtained from you to identify the daily variations of nutrients consumed.
Food frequency questionnaire-As the participant, you will be provided with a close-ended questionnaire with a list of foods against the number of times consumed in a certain period, from which you will be required to cross-check the particular food item and the number of times consumed during the required period. Using this method, data can be collected on a daily, weekly, monthly or annual basis. You may also be required to provide information about the amount of food intake.
Dietary history– It is an informed account that designates normal food intake within a long duration of time (approximately 6-12 months). For example, a participant may be asked what they usually have for lunch and will be required to enlist the daily variations of nutrient intake. The examiner may continue to probe to determine a full description of the food variety consumed during lunch. The participant may further be requested to estimate portion sizes using household measures alongside the frequency of intake. This process of interviewing will also be applied to other meals during the day.
As for prospective methods, the following methods are applied:
Estimated food records– You as the respondent, will be instructed to record all foods and beverages consumed within a required time period. You will be trained on how to weigh foods under adequate supervision from nutrition personnel before the commencement of the study. The period to participate in study will depend on the study’s objectives. Studies that aim to establish habitual intakes for respondents may take longer. When recording, you will need to include time of the day when food or beverage was taken, the location and even brand names. To estimate food portion consumed, food photographs and standardized household measures will be utilized. For persons who cannot record their consumption, assistance from caregivers will be required to weigh and note down the food consumed. Once data collection is completed, an analysis will be performed using a food composition database.
Weighted food records -It is frequently considered the most accurate method for providing estimations of nutrient intake. You will be trained on how to weigh foods under adequate supervision from nutrition personnel before the commencement of the study. After the training period, you will b required to weigh foods consumed using weighing scales. Foods consumed outside the house can also be weighed or you will be asked to give a description of the foods and location they were consumed at. The examiner will then purchase the food from eatery or shop to weigh the accounted portion size later. For persons who cannot record their consumption, assistance from caregivers will be required to weigh and note down the food consumed. When the process is completed, the information from the weighed food record will be assessed; the data will be converted to nutrient intakes using an analysis system and a food composition database.
Duplicate meal method-This method involves the setting aside of duplicate portions of all beverages and foods taken through a particular time period. The duplicate portions set aside are weighed either by you as the respondent or by the interviewer, and then submitted to laboratory for chemical assessment to determine nutrient measures. You will be needed to maintain a food diary where you record the beverages and foods taken and to offer information on their portion sizes.
In recent times, the application of innovative technologies such as mobile-based technologies and interactive computer and web-based technologies have also become important, and are extensively used in dietary data collection.