A comparison of three different method for the estimation of dietary intake

Abstract:

Energy intake surveys form an integral part of studies aimed at assessing food security. In the present study three methods especially the 24-hour recall method, the 7-day weighed dietary record method and the duplicate diet method were performed and evaluated for their efficiency to estimate the food intake as accurately as possible. It was found that the duplicate diet method was the best as it involved laboratory analysis of foods for calculation of energy content rather than rely on established tables and websites for the same. Also it was able to predict the exact energy amount consumed which is a very important step in food security survey to assess health.

Introduction

Energy is a very important term with respect to dietiticians and people committed to maintaining a healthy lifestyle. It is very essential to understand the relevance and energy content of different foods taken so as to assess suitability, benefits and problems arising due to controlled and uncontrolled diets. Although there were ideas existing among people regarding dietary calculations and food content, actual regulations and requirements were proposed only during the Second World War (Nestle, 35). A number of survey methods are available for assessing food intakes (Dwyer, 1994; Gibson, 1990; Willett, 1998). The surveys conducted for estimating dietary intake are broadly classified into those that calculate food intake in the past (retrospective) and those that are happening at present (Current). Each method has several sub-categories under it. The retrospective intakes method is questionnaire based and is further subdivided into dietary history, food-frequency and 24 hour recall categories while current intakes are subdivided into dietary records and chemical analysis of duplicates. Each of these categories has their strengths and weaknesses and selection of the appropriate method is based on requirement, appropriateness, cost, user-friendliness and fastness of application. The dietary history is a method involving a systematic recording data acquisition by questioning a person about food habits and recording the food consumed over a period of three days (Burke, 1947). The food-frequency method was developed by Wiehl and Reed, in the year 1960. This involves providing a questionnaire during a personal interview, over telephone or by post to individuals to record their food intake. This questionnaire contains a list of food items from which a person can choose. The 24 hours recall method involves a systematic recording of food intake details provided by an individual over the past 24 hours.
The dietary record is considered as one of the bets among the food survey methods as it involves a systematic weighing of food stuff consumed over a period of one to seven days, the number of days is determined by the nature and number of subject/subjects, type of nutrient and differences existing within the same respondent or between respondents (Bingham, 1987). This method is so accurate that it has been and is used to evaluate the benefits of other old and new methods relative to it. The weight of foods can be estimated in an accurate manner by actual weighing (precise weighing method) or by approximation (estimated food weight record). The chemical analysis of duplicates method involves a duplicate collection and storage of food items in separate boxes every time a food item is consumes. This kind of survey is done over a 24 hour period but may be extended. In this method also one can collect duplicates by weighing the exact amount of food consumed and taking the same amount for duplicate collection and storage or collect a portion of the food consumed or make a list of all food items consumed as per dietary history and then collect samples of all the foods consumed by the subject. The weighed samples of food substances are then taken to a lab for analyzing the nature of constituents. In the present study, three methods for estimation of dietary intake such as 24 hour recall, 7 day weighed record method and duplicate diet methods were compared to get an idea of the advantages and disadvantages of one method over the other.

Methods

Dietary intake was measured using three different survey methods such as:

1. 24-hour dietary recall method: This method was used to estimate the food intake of an individual over a 24 hour period. The whole procedure was done by arranging an interviewer. The arrangement is done such a way that a person acts as an interviewer from another person (usually a colleague) during data collection and who later becomes the interviewee when his/her data is collected. The interviewer should be as disarming and as casual as possible. Data was collected after following four stages pf processing. In stage one, a complete list of all the food items consumed during the past 24 hours was listed. A thorough listing of all food items need to be done, including alcoholic beverages. In step two a detail description pertaining to each food item such as manufacturer name, preparation method, the time and place of consumption. In stage three, the amount of each food consumed was recorded. Units such as milliliters, pints and cups were used to record fluid volumes while grams, pounds and ounces were used to record solid foodstuffs. At the end of data collection, all the different food items are converted to grams using the “Food Portion Sizes” handbook. To assist the respondent in estimating food, household measures and interactive pictorial food atlas were used. In stage 4, all the data recorded were recapitulated and re-confirmed with the subject to control for inadvertent omission. The 6th edition of McCance and Widdowson’s “The Composition of Foods” book is used for the purpose of estimating respondent intake of energy, protein, fat, carbohydrate, non-starch polysaccharides, iron and calcium. Finally, the information report pertaining to energy content of food consumed was handed by the interviewer to the respondent and the respondent should be thanked for his/her time (Gibson, 1993).
2. 7-day weighed record method: This method is same as the 24-hour dietary recall method. This method records quantitative data on food stuffs consumed over seven days. The respondent is instructed to weigh all foods and beverages consumed. Details of the method of food preparation, description of foods, and brand names (if known) should also be recorded. Other minute details listing all the constituents of a food preparation, vitamins and mineral supplements used are also recorded. Often foods that are eaten away from home cannot be measured, so respondents are asked to record the descriptions of the amounts of food eaten using household measure to describe portion size. If the weight food record method is to be used, respondents must numerate and literate. They must also be highly motivated because this method is more time consuming than a 24-hour recall, and the respondent burden is higher. Electronic scales will be provided to allow respondents to weigh food accurately. The remaining leftovers from some items are weighed and subtracted from the total amount to arrive at the amount actually consumed (Adapted from Gibson 1993). Different parameters regarding food intake items such as energy, protein, fat, carbohydrate, non-starch polysaccharides, iron and calcium were estimated using Foodbase, a computerised software package for dietary analysis.
3. Duplicate diet method: In this method respondents collected an identical portion of all foods and beverages consumed during a specified period, usually 24-four hours. Adequate care was taken to ensure that the duplicate portions were identical in both weight and content. For example, while having a meat pie, the portion consumed and the portion collected for analysis were compared and adjusted so that both contained similar amounts of meat and pastry. In addition, respondents kept a written record of food intake to ascertain the foods and quantities consumed. Separate bottles were kept for storing the duplicate set of solids and liquids. The amount of water consumed was neglected, however, drinks with a nutritional content, e.g. alcohol, tea and coffee with milk and/or sugar, juices were measured and stored in duplicate sets. The duplicate diet collection was then taken to a laboratory for chemical analysis of nutrient content. This method avoids the use of composition tables and the inherent limitations of this data. It has the strength of potentially providing a more direct and thus accurate determination of actual nutrient intake, compared with calculations based on food composition data. Sometimes when eating out where it was not acceptable to weigh out exact portions, two portions of each item eaten were bought. From this half was eaten and the rest was stored as duplicate set. For example, while having a burger outside; it may not be able to weigh the bun, burger, relish and salad. It would therefore be acceptable to buy another burger and add it to the collecting pot without weighing. Respondents were clearly instructed to record as much information as possible in their diet diary as it would be required at a later stage for further analysis. Certain items such as sweets or other very hard foods that may not be easy to homogenize while performing food analysis in the laboratory were collected in a separate plastic bag and not added to the rest of the duplicate diet. Last but not the least, all the food items in the duplicate set were kept refrigerated to prevent bacterial consumption. This was also done until two days before commencement of laboratory analysis.

Results

24-hour dietary recall method: In this study, the seventh day was taken as the day for 24-hour recall. Basically all the items consumed on the sixth day were recalled on the seventh day and their energy content were calculated (Figure 1). Energy from unsaturated fats was measured by subtracting energy from saturated fats. Similarly energy from carbohydrates other than sugar was calculated by subtracting energy from sugar from that of carbohydrates. It was seen that the diet included mainly carbohydrate and unsaturated fat and was low in protein.
7-day weighed record method: The seven day weighed method produced interesting results. The data was expressed as energy consumed constituent wise for each day (Figure 2) as well as a mean for all the days (Figure 3). It was seen that carbohydrate intake and fat intake was definitely more than proteins for all the days. The amount of unsaturated fat intake is more than saturated. The same trend was seen when mean energy consumed constituent wise was plotted (Figure 3).
Duplicate diet method: The seventh day of the 7-day weighed method was taken for collecting and measuring food amounts for the duplicate diet method. It was seen that again carbohydrates were consumed more than fats which in turn were more compared to proteins. Also unsaturated and saturated fats were taken in almost same amounts.

Discussion

The different methods give an estimation of the energy content of the food consumed. All the methods agree on the fact that there is more carbohydrate intake in the diet. However, all the three methods report different amount of proteins consumed. Also in the case of the amount of unsaturated versus saturated fats there is strong disagreement between the three methods. The differences are mainly due to two biases present in the 24-hour recall method and the 7-day weighed record method. These are called Random bias and Systemic bias. Random bias refers to the situation or error occurring due to the randomness of food intake which means there is no control of the type of food taken (Bingham, 1987). This can be eliminated by increasing the number of days or by using sophisticated statistical methods. Systemic bias refers to under-reporting which usually occurs due to lapses in memory or wantonly omitting certain food items. Considering all this, the duplicate diet method is the best of all the methods. It is actually a gold standard for assessing the efficacy of newer survey methods.
Since very less protein is taken in the diet, it is very deleterious because protein is needed for normal tissue repair and cellular function (Table 1). The fat content especially the saturated fat is almost same as the amount of unsaturated fat consumed thus posing a severe health issue. The high levels of saturated can cause atherosclerosis and subsequently heart problems. The total energy also decreases from day one to day seven suggesting decreased intake or low quality food. There was also a decrease in iron intake noted which could lead to anemia. Likewise low calcium levels could lead to calcium deficiency or parathyroid gland hyperactivity. Only the duplicate diet method gives an exact reflection of the energy from unsaturated and saturated fat. It is very important because an alteration in the ratio could lead to devastating effects on health.
The day chosen for the 24-hour recall and for the duplicate diet was appropriate because any other day chosen during the 7-day weighed dietary method would have resulted in more systemic bias. Out of the three methods, duplicate diet method is the best and does not have the many disadvantages seen with the other two methods. The other two methods are subject to random and systemic bias. Also in the former two methods, estimation of caloric content is done based on published guidelines, books and softwares. But these are not accurate as the caloric content of the food changes with advancement in food quality both due to additional ingredients and due to hybrid varieties. The other methods that can be used in the study are dietary history and the food frequency questionnaires method. But these also have a lot of demerits. Thus the best method is the duplicate diet method which is constrained only by the cost factor and the burden on the respondent.

Conclusion

The advent of different survey methods and software programs has definitely our understanding of nutritional value of foods and also the amount of intake needed to maintain a healthy pattern of life. The three survey methods used in the present study definitely have advantages and disadvantages. After assessing all the three methods it is concluded that the duplicate diet method is the best with respect to accuracy and limited bias.