IX. DIETARY SURVEY

The Wartime Social Survey in collaboration with the Ministry of Health has worked out a method of estimating individual diets which can be applied to large groups.

The method has so far only been used for Schoolchildren but could be applied to any particular group or groups of the population.

The informants selected were given forms (Appendix III) and asked to put down exactly what they had for their meals during a week. They were asked to write down the food they had, and to write it at the time of the meal or immediately after.

For quantities homely measures were used; all food was measured out in table or tea spoons (standard sized spoons were provided for the purpose) as far as possible. A poster was provided to show how much should be put in a tablespoon.

For such foods as potatoes, cheese, meat, which could not be measured in spoons, the poster (Appendix III) showed pictures of different sizes, which were labelled with letters, and the informant was asked to compare the size of the food with those on the poster and enter the appropriate letter on the record form.

The informants were asked to use the same cup for all drinks during the week. The field-worker measured the content of the cup. The informants were also asked to indicate how thick they usually cut slices of bread; this thickness was measured by the investigators, and only the number of slices eaten had to be recorded.

Whenever the informants took a meal outside the home it was recorded; if these meals were school meals for children, canteen meals or British Restaurant meals for adults, the constituents and quantities of the meals were obtained from the school canteens and feeding centres, who measured these over a period, so that average quantities were arrived at. School milk, where taken, was also recorded.

In order to get some idea of the Vitamin C wastage in cooking, which varies with different cooking and serving habits, samples of cooked vegetables were obtained, and analysed for Vitamin C content by a member of the Dunn Nutritional Laboratory (Cambridge) Staff. Informants were also asked their methods of cooking, and with this information it was possible to arrive at approximations of Vitamin C content of the vegetables consumed.

About 68%-70% of the people approached were able and willing to keep such a record of their food intake for a week. The amount of help which the field-worker had to give varied; in some cases it was enough if the informants were visited three times during the week of the experiment, in other cases they had to be visited every day.

The real difficulty of a dietary survey generally is not so much the obtaining of the material as the statistical analysis. The method used by the Wartime Social Survey is as follows:-

Foods are classified into 68 groups and the unit quantity determined with a view to convenience in collecting and coding the information. The range of intake of each foodstuff goes up to the greatest quantity of the food eaten by any one during one day. The table (Appendix III) shows the nutrient value of one unit of each foodstuff and the range of intake. A set of ‘ready-reckoner’ cards is prepared giving for every foodstuff the nutrient value of each quantity to the extent of the range.

From the coded forms for each informant one card is punched for each foodstuff eaten during one day. An average of 15 different foods are taken every day, thus some 105 cards are punched for each individual - a total of about 50,000 detail cards for 500 informants. These detail cards are hand-punched with the day-code, the food-code and the quantity. The individual’s number and sociological data are gangpunched on to each set of 105 cards.

The 50,000 detail cards are mechanically sorted with the ready-reckoner cards on foodstuff and the quantity within each foodstuff group. Nutrient values on the ready-reckoner cards are then mechanically reproduced on to the appropriate detail cards.

The next operation is to sort the detail cards on a sorting machine to each person’s number, after which two tabulations are prepared which give (a) a list of total quantities of every foodstuff eaten by each informant during the week of seven days and (b) the total daily nutrient intake of each individual.

Comptometer totals from the forms are checked against tabulation (a). Tabulation (b) consists of 3,500 lines (500 persons x 7 days) and a summary card is hand-punched for every line of this tabulation. Thus these summary cards contain the sociological information relating to each person in the sample and his/her total daily nutrient intake.

Finally, the summary cards are sorted and tabulated to give the total nutrient intake of all the informants in certain groups. Some we are using so far are:-

From these group-totals group averages are computed.

A table is made by hand from tabulation (a) showing for each of the informants the weekly menu and the quantity of the various foods that comprised the menu. For this purpose the original 68 foodstuff-groups are reduced to about 25. One card is hand-punched for each informant with the menu and sociological details and these are analysed in the same way as the summary cards containing nutrient intake, except that their averages are computed per week instead of per day.

The Hollerith machines used are:-

It takes about three months to complete a dietary survey for 500 people of this kind from the beginning of the field work to the date when the final results are available.