248 Introduction to Human Nutrition
of all food and drink consumed during the specifi ed
period if it refl ects all foods and drinks consumed in
the amounts that they were actually consumed. It may
not, however, be a valid refl ection of habitual intake
if the items consumed were not typical of the indivi-
dual’s usual intake.
Determining the validity of a dietary technique has
been impossible in the absence of external markers of
intake, except for the 24 hour recall or for individual
meals.
Methods for measuring intake on
specifi ed days
Menu records
Menu records are the simplest way of recording infor-
mation on food intake. They only require the respon-
dent to write down descriptions of the food and drink
consumed at each meal and snack throughout the day
for the specifi ed days without quantifying the por-
tions. A menu record is useful when information on
food patterns rather than intake is required over a
longer period or when respondents have diffi culty in
providing quantitative information. For example,
elderly people may have diffi culty in reading the divi-
sions on household scales or in measuring out food
portions. To derive information on nutrient intake
from menu records investigators also need to obtain
information on portion sizes of commonly eaten
foods. Information on portion sizes may be derived
from existing data or collected in a preliminary study.
Menu records work well when the diet is relatively
consistent and does not contain a great variety of
foods. The method can be used to distinguish differ-
ences in the frequency of use of specifi c foods over
time, to determine whether quantitative short-term
intake records are likely to be representative of habit-
ual intake and as a way of assessing compliance with
special diets.
Weighed records
Weighed records require the respondent, or a fi eld-
worker, to weigh each item of food or drink at the
time it is consumed and to write down a description
of this item and its weight in a booklet specially
designed for this purpose (sometimes referred to as a
food diary). Weighed records are usually kept for 3, 4,
5, or 7 consecutive days. To obtain accurate informa-
tion it is necessary to use trained fi eldworkers to
collect the data or to demonstrate the procedures and
to provide clear instructions to the respondents not
only on how to weigh foods but also on how to
describe and record foods and recipes. When respon-
dents are responsible for weighing, the investigator
needs to make regular visits to the respondent during
the recording period to ensure that the equipment is
being used correctly and that information is recorded
accurately and in suffi cient detail.
Weighing can be carried out in two different ways:
1 The ingredients used in the preparation of each
meal or snack, as well as the individual portions of
prepared food, must be weighed. Any food waste
occurring during preparation and serving or food
not consumed is also weighed.
2 All food and beverage items are weighed, in the
form in which they are consumed, immediately
before they are eaten, and any previously weighed
food that is not consumed is also weighed.
The fi rst approach is sometimes referred to as the
precise weighing technique and is usually carried out
by trained fi eldworkers rather than the respondents
themselves. It is thus very labor intensive, time-
consuming, and expensive to carry out. It is most
appropriate when the food composition tables avail-
able contain few data on cooked and mixed dishes or
if exposure to contaminants is being assessed. It
should be noted, however, that the precise weighing
technique does not allow for nutrient losses in
cooking. To take these into account information on
cooking losses for the most commonly used cooking
methods must also be available.
The second procedure, which is more widely used,
involves weighing all food eaten in the form in which
it is consumed. It is sometimes referred to as the
weighed inventory method. Using this method the
nutrient content of the diet can be determined either
by chemical analysis of duplicate portions of indi-
vidual foods or aliquots of the total food consumed
or, most often, from tables of food composition.
Scales used for weighing food need to be robust and
able to weigh up to 2 kg, accurate to at most 5 g and
preferably to 1–2 g. Digital scales are preferred as
these are more accurate and easier to read than spring-
balance scales. Record books must have clear instruc-
tions, be easy to use, and of a convenient size. They
should contain guidelines for weighing and examples
illustrating the level of detail required. Figure 10.3
shows an extract from the instructions and record