Human Nutrition

STUDIES OF NUTRITIONAL STATUS ❚
Obtaining dietary intake information from
children and adolescents poses particular challenges.
With young children, below the age of
8 years, the limiting factors are likely to be
knowledge of the names of foods as well as limited
attention span and memory. The use of a
surrogate reporter may introduce bias. As children
become older, the ability to record the food
intake increases, but at the same time there may
be a greater desire to ‘please’ the interviewer and
accuracy of records may be low. There are no
easy solutions to collecting dietary intake data
in these age groups, and new or refined survey
methods are needed. Some of the problems
found in this group include underreporting and
non-response, which are also discussed below.
In the last few years, there has been recognition
among nutritionists that much of the
dietary intake data that are collected contain an
element of underreporting. This is confirmed by
comparison of energy intake with calculated or
measured energy expenditure in many different
groups. Measurements of energy expenditure
using the doubly labelled water technique are
available in some research settings. Biomarkers
such as urinary nitrogen levels can also be used
to confirm the accuracy of food intake records,
although these increase the intrusion of the
method, and could reduce compliance.
General findings, for example, based on studies
of 77 groups (reported by Black, 2001) show a
ratio of energy intake to energy expenditure of
0.83 (when a ratio of 1.0 would be expected). In
addition, there is variability between subjects in
the extent of misreporting. For 29 per cent of the
groups studied, results for energy were within
10 per cent of those for expenditure. In 69 per
cent of the groups, energy intake figures were
more than 10 per cent below energy expenditure.
Only in 2 per cent of the groups were the intake
results more than 10 per cent greater than the
expenditure results.
In summary, food intakes are usually underreported.
This has implications for the calculation
of energy intakes, but also nutrient intakes.
If nutrient intakes are expressed in relation to
the total energy intake, a measure of the nutrient
density of the diet can be obtained, expressed
as the weight of nutrient/MJ or 1000 Calories.
This can then be used for comparison between
Activity 1.3
1 With a partner, try out a diet history interview
on one another.
a Go through all of the times in the previous
day when your partner might have eaten
something, and ask him/her questions
about it.
b Try to find out how much of everything
they ate, how it was prepared, what brand
name they had.
c Did they eat all of it, or were there any
left-overs?
2 Reflect on how easily you managed to complete
this activity.
a Did you and your partner have a pattern of
eating?
b How easy was it to assess amounts of food
eaten?
c Did you have the same ideas about what was
a small/medium/large serving of a food?
d Could you remember everything you had
to eat 2 days ago, 3 days ago, etc.? How far
back would your memory of your diet be
reliable?
individuals, even if underreporting has occurred.
These findings raise concerns about the accuracy
of dietary intake studies, and underline the
need for new methods to be developed that can
more accurately capture information about individual
intakes. Alternatively, more precise techniques
for validating the intake records are
needed.
Studies of nutritional
status
These include measurements of:
■ anthropometric indicators
■ biochemical indicators
■ clinical indicators.
Anthropometric indicators
Anthropometric (literally ‘measuring man’) indicators
are basic measurements of the human
body. By relating these to standards typical
of the test population, any deviations indicate
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