Reviewer's report
Title:Disparities Exist Between National Food Group Recommendations and the
Dietary Intakes of Women
Version: 1Date:31 May 2011
Reviewer: malcolm rily
Reviewer's report:
This manuscript assesses the dietary intake of a cohort of Australian women
aged 25-30 years against public health dietary recommendations and finds that
many women do not follow dietary recommendations. The manuscript makes a
case that some women who do not follow dietary recommendations appear to
have an adequate diet, and that dietary recommendations should be developed
to accommodate them. It has been shown many times that generally few people
follow all dietary recommendations and there is interest in how this could be
improved.
- Major Compulsory Revisions
1. It is incorrect to assess the dietary intake of a cohort of women against dietary
recommendations for pregnant women or breast-feeding women. If they are not
pregnant or breastfeeding, the recommendations are not appropriate to them
(final 2 major categories in Table 3 and 4). For this reason, the prevalence of
cohort women who meet these recommendations is meaningless (results,
paragraph 8). Strictly, for the comparison to adult recommendations, the women
who were pregnant, or had been pregnant in the previous 12 months (both
measured for the sample) should be removed because the reference period for
the FFQ was the previous 12 months. A comparison of pregnant women to the
dietary recommendations for pregnancy might be inserted into table 3 with full
discussion of the problems of making this comparison when the FFQ reference
period is longer than the period of the pregnancy. Table 4 should not be retained.
2. The authors identify those women who consumed simultaneously the
estimated average requirement (or higher) for folate, iron, calcium, and zinc; and
the Adequate Intake for fibre while consuming less than the recommended
number of serves of ‘extras’. The diet of these women are categorised as
‘optimal diet’ and their food intake pattern is compared to the recommended food
intake pattern. The different average intake of food groups serves to that
recommended is offered as evidence for the need for alternative food group
recommendations. There are a number of problems with this – perhaps the most
important being the difference in nutrient targets (the development of the AGHE
considered many more nutrients and used different nutrient reference standards).
While the dietary intake is labelled ‘optimal diet’ there is insufficient evidence to
determine whether they represent a nutritionally adequate diet. Furthermore,
when a distribution of nutrient intake is compared to an estimated average intake,
those falling below the EAR are not necessarily having an inadequate intake
because the individual requirement is not known. The method used appears to
assume that women with an intake above the EAR have an adequate intake for
this nutrient – this is not the case. The development of the AGHE
recommendations was based on ‘optimising’ serve recommendations to achieve
nutrient targets in minimal energy intake – it is well recognised that there are
dozens if not hundreds of alternative eating patterns that also achieve a similar
nutrient intake. While the authors call for ‘revised food selection guides’ providing
‘greatest flexibility’, this should be considered in the context of a large number of
different recommendations for the same demographic group. When
re-constructed with the correct data, the authors should consider what the ‘adults’
column of table 3 is saying – having identified all women meeting the nutrient
targets, they have dichotomised them into those who meet an ‘extra’ foods target
and those who don’t. Those having a ‘high extras diet’ at present appear to have
almost 5 more serves (on average) than those who meet the extra foods target –
they also have more daily servings of meat or alternatives (by an average of 0.6
serves) while the only compensating food group is dairy (with a difference of 0.3
servings in mean intake). The mean energy intake between the groups is very
large – 3.1 MJ/day. This is difficult to interpret and perhaps should wait until the
appropriate data is used – both of these groups appear to have a high food
intake compared to the rest of the cohort (i.e. compared to table 2 final column)
which is a reminder that nutrient intake is correlated with reported energy intake.
3. The problem of the dietary measurement instrument covering a reference
period that is inconsistent with the categorisation of subjects is a major issue
which is only covered briefly late in the discussion. The dietary recommendations
for pregnancy are only intended for women who are pregnant, and the FFQ is
intended to measure usual diet over the previous 12 months (which clearly
covers some time pregnant, and some time not pregnant). It seems very difficult
to sustain an argument that the FFQ measures usual diet at the time of
completing the questionnaire (i.e. that the FFQ is invalid for its intended task, but
valid for a different task) particularly when it has been stated that the FFQ has
been validated. It is unlikely that the FFQ has been validated for the specific
categories of women defined in this study – this could be a discussion point.
However, the comparison of the dietary intake of women who are currently
pregnant with dietary recommendations for pregnancy using an instrument
designed to measure usual diet over 12 months is not very satisfactory. On this
basis, one would expect the dietary intake of women who were pregnant to be
similar to that of women who had given birth less than 12 months previously –
except there is the added complication of higher nutrient demands of
breastfeeding which would have occurred for different periods of time in one
group only.
- Minor Essential Revisions
4. In the abstract, include the age range of the women and the date of the data
collection.
5. NRVs refer to a range of values - throughout the manuscript name the actual
reference value intended rather than the generic term.
6. Throughout, take care to represent the data as cross-sectional data. For
example, the authors state (results, paragraph 4) ‘‘Pregnant’ women reported
increases in the daily grams of both fruit ...’ where a more appropriate alternative
is ‘‘Pregnant’ women reported a greater mean daily intake of both fruit ... ’.
7. The reference period for the FFQ is included in the discussion – it should be
stated in the methods.
8. Demographic variables should be provided by ‘pregnancy’ category.
9. The sample is stated to be broadly representative of the general population of
Australian women – from the reference cited, this must have been at recruitment.
This should be stated, with the factors that were assessed, and a statement of
the follow-up rate at survey 3.
10. The method of administration of the FFQ should be included. The method of
converting the FFQ categories into the AGHE categories should be given (a
conversion table might be shown unless each category had an unambiguous
assignment).
11. The statement (statistical analysis, paragraph 2) ‘variations in food group
intakes were analysed using the chi-squared statistic’ does not make sense to
me – was food group intake treated as a categorical variable? Or does this refer
to Table 4 comparison of demographic variables between groups? Was there
any examination of the distribution of food or nutrient variables – these are often
highly skewed.
12. Little time is spent considering the validity of the dietary data although it
would appear that 1418 subjects were excluded on the basis of inaccurate
energy estimates (too high or too low – no discussion). While the FFQ is stated
to have been ‘validated’ with an appropriate citation, the possibility of an
inaccurate dietary instrument for measuring usual dietary intake over a 12 month
period is critical for the focus of the study. The total estimated mean daily food
weight is shown in table 2 to be 1392 g with a daily mean energy intake of 7521
kJ – this could be compared to relevant data for this age group even if it means
using the 1995 national survey data.
13. As explained elsewhere, because there appeared to be no measurement of
whether a woman was breastfeeding or not, and because the FFQ was intended
to cover a 12 month period, it appears spurious to compare the intake of any of
the women with recommendations for breastfeeding (results, paragraph 5).
14. Note that the mean intake of ‘extra’ foods for women categorised as ‘High
extras diet’ was 6.5 – 8.0 servings a day rather than 6.5-7.3 as stated in the text
(results paragraph 7)
I think that the problems with the dietary measurement instrument reference
period in relation to the ‘pregnancy’ status classification of the women undermine
a lot of the rationale for the study. It would be possible to assess the dietary
intake of women who were not pregnant at the time of the study or 12 months
previous to it against dietary recommendations, and to compare women
intending to become pregnant to those who weren’t – this appears to be a
different manuscript however.
Level of interest: An article of limited interest
Quality of written English: Acceptable
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
I worked for Dairy Australia – a dairy industry services organisation – from
2006-2010. I declare that I have no other competing interests.