Responses to Reviewer #1 regarding MS: 2126389878105171
To Reviewer #1:
We would like to thank you for your helpful and pertinent comments. Our point-by-point
responses to your comments appear below. We hope our revised manuscript will now prove
acceptable for publication in BMC Public Health journal.
Comments.
The author can be trusted to make these. For example, missing labels on figures, the wrong
use of a term, spelling mistakes. This manuscript uses existing data to examine changes in
food intake over time in Japan. This analysis identifies trends which may have implications for
diet related health in Japan in the future.
Comment1
In general avoid using ‘effects’ to describe observed associations, eg ‘obvious effects of birth
cohort in abstract conclusion.
(Our response)
Thank you for your comment. As the reviewer suggested, we limited our use of ‘effects’ as
much as possible when referring to associations. We revised the manuscript throughout
including the specific example indicated by the reviewer.
*Revised page 2, line 12:
Both men and women in the 1940’s birth cohort consumed more fruit although differences in food and
nutrient intakes by birth cohort were less discernible
*Revised page 14, line 11:
Differences in food group intakes by birth cohorts born between 1930 and 1979 were not obvious.
Comment 2
The remainder of the sentence that starts with ‘Although there were no obvious effects of birth
cohort …’ is not well written and the meaning is unclear.
(Our response)
As the reviewer suggested, we revised the sentence both in the abstract conclusion and
conclusions section as follows:
*Revised page 2, line 20:
These findings indicate that the future health status of recent younger individuals may not be as good
as that experienced by other Japanese generations due to their consumption of less healthy foods.
*Revised page 14, line 12:
These findings indicate that the future health status of the younger individuals might not be as good as
that experienced by older Japanese generations due to their consumption of less healthy food.
Comment 3
Overall the manuscript could do with careful editing to improve the grammar.
(Our response)
The manuscript has been edited again by a native English editor who works for the science
communications company, FORTE. This company provides professional translation and
editing services. We are submitting certification that this manuscript underwent editing at this
company. If the grammar in the revised text is still not satisfactory, please let us know.
Comment 4
1
At the start of the second paragraph on page 4 increasing fat intake (over time) especially in
younger adults is noted. This is not similar to studies showing a decline in food intake with
ageing.
(Our response)
As the reviewer pointed out we revised conjunction as follows:
*Revised page 4, line 12:
On the other hand, cross-sectional and longitudinal studies in Western countries indicate a decline in
food intake with aging [7, 8]. Total energy intake is reported to decrease with age [9], along with
diminished taste and smell [10, 11].
Comment 5
If the sampling frame for each NHNS-J was the same at each survey why were there so many
more participants in 1999 and 2009? Does this just reflect the variation between the districts
surveyed?
(Our response)
Total study participants in the 1989 survey was not actually small (approximately n=20,000)
compared to that in the 1999 or 2009 survey (approximately n= 15,000). But sex- and
age-stratified nutritional intakes were publically opened only for single-person households in
the 1989 survey. We added the following sentence to explain it and representation of the
single person household:
*Revised page 5, line 21:
Although the number of total study participants in the 1989 survey was comparable (approximately
20,000) to those in the 1999 survey (n= 15,000) and in the 2009 survey (n= 15,000), sex- and
age-stratified nutritional intakes were publically opened only for single-person households; therefore
the number of subjects in the 1989 survey used in this study was relatively small.
*Revised page 13, line 11:
In addition, sex- and age-stratified nutritional intake per capita in 1989 used in the analysis was
derived from NHNS-J participants living in a single-person household. The representation of
single-person households may be limited. However, the difference in nutritional intake per capita
between single-person and full households in 1989 was not large. For example, the mean energy in
each household was 1980 kcal/day and 2061 kcal/day, respectively [18]
Comment 6
On page 9 in discussion it is preferable not to use ‘Intakes of meat and fat decreased…” as
this sounds like you have assessed a change over time in same people whereas you have
observed that intakes of meat and fat were lower in older people than younger people.
(Our response)
As the reviewer suggested, we revised these descriptions as follows:
*Revised page 10, line 1:
Meat and fats and oils intake were lower in older age groups of both sexes than the younger groups.
*Revised page 10, line 7:
Intake of fruits, fish, beans, and vegetables were higher in older age groups of both sexes than younger
groups
Comment 7
As well as a possible decrease in digestive function with ageing being responsible for
decreasing intakes of fat and meat, an alternative and simple explanation could be the
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reduction in energy requirements with age in relation to reduced physical activity.
(Our response)
As the reviewer suggested, we revised the explanation to include “decline in energy
requirements” and added 2 references, as follows:
*Revised page 10, line 3:
A potential explanation for the lower fats and oils and meat intakes among older adults is the decline
in digestive function and energy requirements that occur with aging in relation to reduced physical
activity [27, 28].
Comment 8
In the comment about older individuals being more prudent in choice of foods than younger
people, is it likely that as people age they become more aware of associations between health
and diet, see their peers get sick or get sick themselves and then are advised to eat more
healthy foods and cut down on those that are considered less healthy?
(Our response)
Good points. We totally agree with the reviewer’s comment. We have made the sentence
clearer by adding why older people would be more prudent in their food choices.
*Revised page 10, line 12:
This would be natural as the older individuals are more aware of associations between diet and health,
and they also may be more conscientious if they or their peers are suffering ill-health.
Comment 9
Why is the extra fruit intake in men born in 1930-39 relative to men born in 1970-79
(3.0+2.7)/1000kcal?
(Our response)
The mean Polish method we used in an attempt to describe birth cohort, time and age effects
on diet uses the following model, where Rij (food and nutrient intakes) is modeled by the sum
of the effects of the ith age group represented by ai, the effects of the jth time period
represented by tj, and the effects of the kth cohort represented by c(k).
Rij = ai + tj + c(k)
A c(k) value greater than zero indicates higher than additive influence and less than zero
indicates lower than additive influence from age/time effects on food/nutrient intakes.
Fruit intake/1000 kcal in men born in 1930-39 was calculated as: Rij = ai + tj + 3.0
Fruit intake/1000 kcal in men born in 1970-79 was calculated as: Rij = ai + tj -2.7.
Therefore, the extra fruit intake in men born in 1930-39 relative to those born in 1970-79, that
is, difference of fruit intake/1000 kcal between these birth cohorts, was 3.0-(-2.7) =3.0+2.7=
5.7g/1,000 kcal.
Comment 10
Are higher rates of marriage and higher average savings in earlier relative to later birth
cohorts independent of age differences? It would be natural for older men to have more
savings and be more likely to be married relative to younger men.
(Our response)
As the reviewer indicated, differences in marriage rates and savings by generation could be
explained by their age differences. However, among Japanese, such differences seemed to
be independent of age. For example, the % of unmarried men aged 25-29 was 35% in 1950,
48% in 1980, 72% in 2005, and the % of unmarried men aged 40-44 was 3% in 1950, 5% in
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1980, 22% in 2005, respectively. Savings seemingly differ among generations too, i.e., recent
generations are reported to have fewer savings at the same age compared to the earlier
generations. Nevertheless, these differences might be influenced time and/or birth cohort
effects. We revised the text incorporating the reviewer’s suggestion as follows:
*Revised page 11, line 19:
Indeed, compared with recent birth cohorts, higher rates of marriage [37] and average savings [38]
are reported among earlier generations of Japanese men and these variables may influence the higher
fruit intakes.
Comment 11
The study found that the intake of fat was lower in more recent years as noted on page 11 in
the discussion, but this is in contrast to suggestion on page 4 that fat intake is increasing over
time. Make it clear that ‘fat’ is a food group rather than a nutrient and specify the foods in this
group.
(Our response)
Thank you very much for the suggestion. Reviewer #2 also pointed out this issue and
suggested clarification. Since we had been using “fat” as food group intake, we changed it to
“fats and oils” in the revised text and tables according to the more accurate term used in the
National Health and Nutrition Survey in Japan.
As the reviewer #1 pointed out, we mentioned in the Introduction “the percentage of energy
obtained from fat increased from 6.9% to in 1949 to 26.5% in 2000 according to the National
Health and Nutrition Survey in Japan”. We provided additional data about percentage of
energy obtained from fat in the 3 most recent decades, these values have little fluctuation
those were 25.7% in 1989, 26.5% in 2000, and 25.6% in 2009, respectively. We revised the
Discussion as follows:
*Revised page 6, line 21:
In order to avoid confusion between fat (nutrient) and fats and oils (food group), we quoted “fats and
oils” when we refer to the food group.
*Revised page 12, line 9:
Even though intakes of fats and oils decreased in Japan, the percentage of energy obtained from fat
increased from 6.9% to 26.5% in 1949 to 2000 NHNS-J, respectively [5]. However, within 1989 to
2009 NHNS-J data, the values fluctuated very little, i.e., the energy obtained from fat were 25.7%,
26.5% and 25.6% in 1989, 2000 and 2009, respectively [5, 19]
Comment 12
In Tables 2 and 3 it needs to be clear within the table, its title or relevant footnotes what the
values actually represent. The tables should be able to be understood independently of the
text. Why not use a ‘-‘ to indicate negative effects or differences?
(Our response)
As the reviewer suggested, we revised the title and added relevant footnotes what the values
actually represent. We also changed the triangle symbol to ‘-’ to indicate negative effects in
Tables 2, 3, and 4.
Comment 13
Table 2 does not show any of these differences as being significant yet in the text the
comments on fruit suggest that this was significant. Was anything significant? Similarly for
Tables 3 and 4?
(Our response)
4
As the reviewer pointed out, we employed the mean Polish process in this study but it does
not provide information about the statistical significance. Therefore we deleted the term
‘significant’ in the text.
Comment 14
In Figure 1 there are some odd errors. Should be weighed not weighet and should be survey
not suevey.
(Our response)
We apologize for the mistakes. We have corrected these words in Figure 1:
“weighet” → “weighed”
“suevey” → “survey”
Comment 15
Would be worth discussing your observations in relation to what is known of other countries.
(Our response)
In the present study, we found that intakes of meat and confectionary have been increasing
in Japan over the past 20 years regardless of the age and generation, and younger individuals
are less likely to consume fruits, fish, beans, and vegetables regardless of the generation and
time period.
As the reviewer suggested, we have cited three longitudinal studies conducted in other
countries that indicated that older adults are making healthier food choices. We also cited
three descriptive studies regarding meat or animal foods intake.
We revised the Discussion as follows:
*Revised page 10, line 14:
In other countries, which are consistent with our findings, several longitudinal studies indicate that
the elderly make positive changes to their diet. Prynne et al. reported that fat intake decreased, while
intake of fruits and vegetables increased in 1253 men and women born in 1946 from the 17 year
British birth cohort study [32]. Fernyhough et al. reported that meat intake decreased in men and
women during their 6-year follow-up of a community dwelling in adults aged 70 years or over in New
Zealand. They examined the association between age, time, and cohort effects, and they also reported
that older adults, particularly women, are making healthier food choices. For example, women ate
brown or whole-wheat bread at the 6-year follow-up [33]. Another study also indicated older women
at baseline made positive changes to their dietary habits; however, these changes may have been
affected by the aging process and marital status in a 21-year follow-up among Finnish women aged
50-60 years [34].
*Revised page 12, line 13:
Consumption of meat and animal food products in the last few decades also increased in South Korean,
India, Spain, and Middle East and North Africa [43-46]. These studies, however, did not examine
possible effects of time, age, and birth cohort effects on diet.
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Responses to Reviewer #2 regarding MS: 2126389878105171
To Reviewer #2:
We would like to thank you for your helpful and pertinent comments. Our point-by-point
responses to your comments appear below. We hope our revised manuscript will now prove
acceptable for publication in BMC Public Health.
Reviewer's report:
This manuscript is well-written and insightful into public health nutrition. Few studies have
examined the association of dietary intake with age, time and birth cohort effect. I have few
comments for the authors.
Discretionary revision
Comment1
Authors can use “Fats and Oils” instead of “Fat”, because former is used as food group intake
and latter is used as nutrient intake in the National Health and Nutrition Survey in Japan.
(Our response)
As both Reviewer #1 and Reviewer #2 pointed out, we used “Fat” as food group intake, and
we revised it to “Fats and Oils” in the text and tables as per the National Health and Nutrition
Survey in Japan.
*Revised page 6, line 21:
In order to avoid confusion between fat (nutrient) and fats and oils (food group), we quoted “fats and
oils” when we refer to the food group.
Comment 2
Reviewer recommends that the authors add data-based discussion using published data of
1989 NHNS-J about the representativeness of single-person data.
(Our response)
As the reviewer suggested, we added the discussion about the representation of
single-person data using published data of 1989 NHNS-J as follows:
*Revised page 13, line 11:
In addition, sex- and age-stratified nutritional intake per capita in 1989 used in the analysis was
derived from NHNS-J participants living in a single-person household. The representation of
single-person households may be limited. However, the difference in nutritional intake per capita
between single-person and full households in 1989 was not large. For example, the mean energy in
each household was 1980 kcal/day and 2061 kcal/day, respectively [18].
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Responses to Editorial office regarding MS: 2126389878105171
We thank you for your request. Our response to your comment appears below. We hope
our revised manuscript will now prove acceptable for publication in BMC Public Health.
Comments
We recommend that you copyedit the paper to improve the style of written English. If this is
not possible, you may need to use a professional language editing service.
(Our response)
As the editorial office and reviewer both pointed out, to improve the style of the written
English, this manuscript has been edited by a native English editor who works for the science
communications company, FORTE. This company provides professional translation and
editing services. We are submitting certification that this manuscript underwent editing at this
company. If the grammar in the revised text is still not satisfactory, please let us know.
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