Nutritional status is often assessed through biochemical analysis. This works for specific nutrients for which there is a measurable indicator. Conclusions on the nutritional availability of iron, e. g., can be drawn from the amount of hemoglobin in the blood. Anthropometrics, i. e., body measurements (see p. 16), provide a more general measure. Besides height and body weight, determination of skin fold thickness has been gaining increasing importance. Anthropometric measurements represent cumulative results of many different factors and do not differentiate among the various nutrients. Clinical symptoms caused by nutritional deficiencies tend to become apparent very late. A long-term low iron supply, e. g., will eventually result in clinical symptoms like pallor and reduced performance levels—symptoms that could have been averted through early intervention.
Direct dietary intake assessment can be ongoing (prospective) or retrospective. With the weighing method, all foods consumed are actually weighed, whereas the protocol method uses amount estimates. The inventory method assesses the food consumption of an entire household by registering use of food items, as well as leftovers and waste. For example, a large amount of food is made available to a family and after a week the remainder subtracted from the initial amount. This method is not suitable for assessment of individual consumption since it does not permit any differentiation between individuals. The accounting method is used in some countries to assess household food consumption for statistical purposes. Selected households keep a record of all food items purchased. Among the retrospective methods, the determination of food frequency is most simple to conduct. Subjects are asked how frequently they consume specific food groups. A diet history is more informative since additional factors like nutrition-related behaviors are also recorded. 24-hour recall presupposes good memory in the participants, as all food items consumed within 24 hours have to be recalled—including their amounts.
Food consumption can also be assessed indirectly through official agricultural statistics. This, however, does not permit differentiation among different segments of the population and does not account for waste.
The results of all methods presented naturally contain errors. In a study conducted with 140 participants (B), a 24hour recall was compared with the "actual" observed food consumption. During the recall, all types of foods were regularly omitted or listed erroneously. Cooked vegetables were omitted in more than 50% of all cases, whereas sugar was listed erroneously in nearly 30% of all cases.
- A. Methods for Nutritional Assessment -
Biochemical analyses Anthropometrics, clinical diagnosis
Weighing, inventory, protocol, and accounting methods
Food frequency Diet history 24 h recall
Assessment e.g. using agricultural statistics
Determination of nutritional status
Assessment of food consumption/intakes
Methods for nutritional assessment
B. Foods Listed in Food Intake Assessment -
Potatoes Bread Coffee Beef steak Milk
Processed meats Margarine Sugar Butter Cheese Juice
Raw vegetables Desserts Fruit Cake
Cooked vegetables Frequency in %
I—□ Omitted I-1 Listed erroneously
I—□ Omitted I-1 Listed erroneously
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