A lot of nutrition research is done through the use of the food history questionnaire. This is different from food recalls in that it is shorter, easier to administer and does not require special interviewing skills.
Sometimes studies need to identify patterns of food consumption in a large population. This is done, for instance, as part of a general population health survey. These are done on a fairly regular basis, usually funded by governments, to be proactive in the formulation of heath related polices. This saves our tax money in the long run.
Food history questionnaires are related to food recalls in that they collect information on commonly eaten foods. These questionnaires tend to be simpler in that they do not seek to know each individual food that was eaten. They ask questions like “When you eat pasta how much do you eat and do you eat it once a week, or 3-5 times a month”. You get the idea. Typically a food history questionnaire will have fewer than 100 such questions.
Before a questionnaire like this can be formulated it is wise to know what kinds of foods the population usually eats. A smaller number of individuals are asked what they ate recently, using the recall format. Using the example above, from the results of these recalls, a pattern of “pasta” consumption can be determined. A composite “pasta” food can then be created and used as the nutrient profile for the “pasta” question in the food history questionnaire.
The downfall is that it is a fairly “blunt” instruments. With a bit of care in its construction some of the bluntness can be removed.
The following techniques can be used to make them better research instruments:
- Make up your own;
- Make them specific to your target population;
- Make them as detailed as possible while keeping them still realistically long;
- Base the questions on foods your population eats. Collect as many food recalls as you can and base the questions on the foods in those recalls;
- Create composite foods from similar foods in the recalls and use those to calculate nutrient contributions for corresponding questions in the food history questionnaire;
- Validate your questionnaire… does it over/under-estimate specific nutrients in comparison to your food recall data?
There is enough variability in food intake and nutrient concentrations of individual foods to try to minimize the effect of further variability introduced by blunt food history questionnaires.
Given the amount of variability in this data it is a wonder that any conclusion can be reached about the predicted effect of a nutrient intervention or of specific nutrient consumption.
By all means find and use good software that will make your task bearable. Variability can only be reduced by eliminating mistakes, using the best sources of data possible and collecting large amounts of data. A significant task indeed.