Cereal fibre intake in Australia: a cross-sectional analysis of the 2011-12 National Nutrition and Physical Activity Survey.
Summary (4 min read)
Introduction
- The analysis of nutrient intakes within population-based surveys can offer insight into relationships between consumption and markers of health, contributing to the evidence-base to inform dietary guidelines.
- Previous studies have considered cereal fibre intake as a summation of fibre sourced from foods specifically within the cereal and grains food group.
- This neglects the contributions from mixed foods and many foods with cereals, or even specific cereal fibres as additives.
- The application of the expanded AUSNUT database to the NNPAS dietary intake data, weighted to account for usual population intake, allows estimation of reported cereal fibre intakes and reported food sources within the Australian population.
Data and participants
- This study used data from the Australian Bureau of Statistics (ABS) Basic Confidentialised Unit Record Files (CURF) for the 2011-12 NNPAS.
- The NNPAS is a subcomponent of the 2011-13 AHS, the most recent nationally representative survey within Australia at the time of this study.
- Details for the specific phases and tools used are provided elsewhere (ABS 2013a).
- The assessment included five phases to develop greater layers of detail and accuracy in the answers provided.
- One day of data were collected for n=12,153 participants, with a second 24-hour recall repeated via telephone for n=7,735 participants, at least eight days after the initial recall.
Estimation of cereal fibre intakes
- The cereal fibre content of each food item reported within the survey was calculated within the expansion of the current AUSNUT 2011-13 Food Nutrient database.
- Food sources listed in the AUSNUT 2011-13 database containing >0.1g of cereal fibre per 100g-food product were considered sources of cereal fibre, based on the limitations of the analytical tests that measure fibre (Prosky et al.
- The method employs a three-step formula using two logistic regression models.
- The first model estimates the individual probability of consumption of the nutrient and the second model estimates intake on consumption days.
- Weighting applied was previously calculated and assigned by the ABS for use in the AHS data (ABS 2013b).
Reporting of nutrient-level data
- Mean and median cereal fibre intake were reported by age, categorised using NRV age groupings (NHMRC 2006) , and gender.
- Values were reported both as absolute cereal fibre intakes and cereal fibre intakes adjusted for daily energy intake (10 MJ/day) reported within the survey.
- Adjusting for energy intake allowed for exploration of the relative cereal fibre density of the diet, as absolute cereal fibre intake may be highly influenced by total energy intake.
- For further analyses of associations, NRV age groupings were dichotomised with participants categorised into those aged less than 19 years (children and adolescents), and those aged 19 years or older .
- Participants within each division were then categorised into quartiles based on energy-adjusted cereal fibre intakes.
Statistical analysis comparing total dietary fibre intakes to cereal fibre intake in adults
- All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS version 21, 2009, Chicago, IL) software.
- Eta squared, calculated as the sum of squares between groups divided by total sum of squares, was used to calculate the effect size.
- A chi-squared analysis was used to compare the proportion of respondents within each quartile of cereal fibre that are meeting the AI values for dietary fibre, set at 25g/day for females and 30g/day for males.
Reporting of food-level data
- Unlike nutrient-level data, major food contributors of cereal fibres were reported using only day-1 dietary intake data from the NNPAS.
- For these purposes of this study, day-1 data were deemed suitable to provide a snapshot overview of food sources of cereal fibres.
- Weighting was not applied to analyses at the food level, as the method was designed for scaling of nutrient intakes.
- Foods were also coded as either core or discretionary based on specific nutrient cut-off criteria outlined by the ABS (2013c).
- The proportion of cereal fibre and the proportion of total intake from core foods were compared between quartiles of energy-adjusted cereal fibre intake.
Cereal fibre intakes in NNPAS 2011-12
- At the time of the survey, median cereal fibre intakes were relatively consistent between all NRV age groups ranging from 5.2 g-6.7 g/d (9.1 g-11.1 g/10 MJ/day) (Table 1 reports median and mean values).
- The highest median cereal fibre (6.7g/d) was reported by persons in the over 70-age group and in the 14-18 years age group.
- The lowest median cereal fibre was reported by children aged 2-3 years (5.2g/d).
Associations to dietary fibre intake
- Table 2 displays the trends between quartiles of energy-adjusted cereal fibre intakes and total dietary fibre intakes.
- For both males and females, mean dietary fibre intake increased significantly with each higher quartile of energy-adjusted reported cereal fibre intake.
- On average, males within quartile 4 consumed 6.13g/day more total dietary fibre than males within quartile 1, while females within quartile 4 consumed, on average, 3.78g/day more total dietary fibre than females with quartile 1.
- Correlations between energy-adjusted cereal fibre intake and total dietary fibre intake indicated a medium positive correlation for males (r=0.345, p=0.000) and a weak positive correlation for females (r=0.225, p=0.000).
Sources of cereal fibre
- On day one of the survey, participants reported consuming 1918 foods containing >0.1g cereal fibre.
- Within this group, regular bread and bread rolls, as well as ready to eat breakfast cereals were the main food group contributors of cereal fibre.
- Relatively high proportions of fibre were obtained from refined cereals (e.g. white bread, instant noodles) even though these would be considered low fibre products, reflecting the reasonably high consumption of such products.
- The percentage contribution to total cereal fibre intakes within these three groups was higher amongst children and adolescents than adults.
- In contrast, participants within the lowest quartile of adjusted cereal fibre intakes (Q1, median intake 6.1g and 6.9g, respectively) were consuming the lowest proportion (55% and 50%, adults and children and adolescents, respectively) of cereal fibre from cereal and cereal-based products, and the highest proportion from cereal based products and dishes (32% and 36%, adults and children and adolescents, respectively).
Core food and discretionary food cereal fibre contribution
- Among adults, core foods contributed 87% of total cereal fibre intakes, indicating that only a relatively small amount (13%) of cereal fibre for adults was obtained from discretionary foods.
- Children and adolescents reported 80% of total cereal fibres from core foods on the day of the survey, indicating a slightly higher contribution (20%) from discretionary food sources.
- The main discretionary sources of cereal fibre for both adults and children and adolescents were from the pastries minor food group (26% and 16% of total cereal fibre from discretionary foods, respectively), as well as cakes, muffins, scones and cake-type desserts minor food group (16% and 13%, respectively).
- The proportion of total cereal fibres from core foods increased linearly for participants within each higher quartile of energy-adjusted cereal fibre intakes.
- In contrast, core foods contributed 74% of intakes in both adult and children and adolescents within the lowest quartile of reported cereal fibre intakes (Q1).
Discussion
- The present study reports an estimation of the usual cereal fibre intakes of Australians based on two days of dietary intake data from the 2011-12 NNPAS.
- Furthermore, it details main food sources of cereal fibre consumed by participants on day-1 of the survey, and presents an analysis of how usual cereal fibre intakes may be associated with total dietary fibre intake.
- The median intakes of cereal fibre were 6.2g/day for children and adolescents and 6.4g/day for adults, equating to roughly 2-3 slices of wholegrain bread, or 2 cups of cooked brown rice.
- Even within the highest quartile of energy adjusted cereal fibre intakes, 82.9% of males and 79.7% of females are failing to meet the AI values.
- There are some limitations to this study.
Conclusion
- This study provides the first quantification of cereal fibre intake within Australia at the time of the study.
- The study indicates that while Australians are consuming cereal foods, the choices they are making are likely more refined, lower-fibre varieties, evident by low cereal fibre intake.
- As there is no distinct group consuming considerably less cereal fibre than others, males and females of all ages are suitable targets for communication and education strategies.
- This may also contribute significantly to an increase in total dietary fibre, as persons with diets highest in cereal fibre tended to have significantly higher total dietary fibre intakes.
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Cites methods from "Cereal fibre intake in Australia: a..."
...To provide an overview of contribution to food group and nutrient intakes, the current analysis was restricted to data from Day 1 of the 2011–2012 NNPAS only, as outlined previously in analyses examining other dietary components in the 2011–2012 NNPAS(25)....
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References
5,387 citations
"Cereal fibre intake in Australia: a..." refers methods in this paper
...Pearson’s r correlation was used to assess effect size based on Cohen’s criteria, where 0.1 indicates a small, 0.3 a medium and 0.5 indicates a large effect size (Cohen 1988)....
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...The effect size was interpreted based on Cohen’s criteria (Cohen 1988), where 176...
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...The effect size was interpreted based on Cohen’s criteria (Cohen 1988), where 0.01 is considered a small effect, 0.06 a medium effect and 0.14 a large effect....
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"Cereal fibre intake in Australia: a..." refers background in this paper
...…the association between fibre intakes and favourable health outcomes is frequently found to be strongest with high cereal fibre intakes specifically, particularly when assessing risk of cardiovascular disease (Pietinen et al. 1996; Rimm et al. 1996; Wolk et al. 1999; Mozaffarian et al. 2003)....
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...The health benefits of a diet high in dietary fibres are well supported (Pietinen et al. 1996; Rimm et al. 1996; Wolk et al. 1999; Bingham et al. 2003) and are currently reflected in dietary guidelines outlined by governments worldwide, including Australia....
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786 citations