To be able to group similar foods and report trends in consumption by food category, a coding or classification system is needed.
There are many ways that foods and beverages can be classified and no single classification system will meet the needs of all users. The design of any coding or classification system should aim to address the requirements of a specific survey, as far as possible.
The purpose of the classification system developed for the 2011-13 Australian Health Survey (AHS), was to:
- enable easy reporting of trends in food consumption and nutrient intake since the 1995 National Nutrition Survey (NNS)
- develop a system that reflects the current food supply but allows room for further changes in the food supply for future surveys
- enable food and nutrient intake data to be reported by food group from the AHS
- provide sufficient flexibility and access to detail to help other users work with the food consumption data with different research and reporting objectives.
About the 2011-13 AHS classification system
The classification system developed for reporting food and nutrient intakes from the AHS was designed early in the survey cycle, in collaboration with the Australian Bureau of Statistics (ABS) and in consultation with a wide range of external stakeholders.
Developing the AHS classification system
The classification system designed for the AHS is largely based on the system developed for reporting food and nutrient intakes from the 1995 NNS, which was developed using the classification system for what is now called the United States National Health and Nutrition Examination Survey (NHANES). A similar classification system was also used in the 2007 Australian National Children's Nutrition and Physical Activity Survey (ANCNPAS).
These classification systems group foods according to a major (2-digit), sub-major (3-digit) and minor (4 or 5-digit) group. This approach has allowed the ABS to report the summary data in formats similar to those used in the past and to assess any broad level changes in consumption over time.
Due to changes in the food supply since the 1995 NNS and the 2007 ANCNPAS, some of the original major, sub-major and minor food groupings needed to be modified. Modifications were also made to ensure sufficient detail was captured to meet the needs of users with different research and reporting objectives and, in some places, to take into consideration the regulatory classification of foods. Food consumption and nutrient data from the 1995 NNS, 2007 ANCNPAS and AHS were used to help decide whether it was feasible to sub-divide a food group, based on the number of people consuming a food and the nutrient profile of similar foods.
AHS classification system structure
As indicated above, the classification system developed for the AHS is based on a three tiered structure, and is described below. The complete classification code is a 5-digit number, which forms the basis of the 8-digit survey ID assigned to each food.
The major group level
The first two numbers in a classification refer to the major food group a food belongs to, based on its key ingredient. The classification system developed for the AHS contains 24 major food groups and they cover groupings such as beverages, cereals, eggs, fats and oils, fish, meat, dairy, fruit, vegetables, legumes and special purpose foods.
An example of a major food group would be:
| Code | Food group |
|---|---|
| 19 | Milk products and dishes |
The sub-major group level
When the 2-digit food group is read with the third digit, the group is referred to as the sub-major food group. The classification system developed for the AHS contains 132 sub-major food groups. It is at this point that considerations such as meat species, plant families, major variations in cooking or processing, or major differences in form of presentation are considered. For example within the major category 'Milk products and dishes', there are separate classifications for milk, yoghurt, cheese, cream, ice cream etc.
In the 1995 NNS, food consumption was reported at this level in the summary report on foods eaten.
An example of sub-major food groups would be:
| Code | Food group |
|---|---|
| 19 | Milk products and dishes |
| 191 | Dairy milk (cow, sheep and goat) |
| 192 | Yoghurt |
| 193 | Cream |
| 194 | Cheese |
| 195 | Frozen milk products |
| 196 | Custards |
| 197 | Other dishes where milk or a milk product is the major component |
| 198 | Flavoured milks and milkshakes |
The sub-major food groups are generally not sufficiently detailed to allow assessment of consumption of similar foods that vary by nutrient profile.
The minor group level
When the first five digits are read together, it represents the 'minor' food groups. The classification system developed for the AHS contains over 500 minor food groups. At this point foods may be separated based on whether or not they are fortified, or have a saturated fat or sugars content above or below a certain value, and other production or processing considerations (e.g. whether cheese is ripened or not).
An example of minor food groups would be:
| Code | Food group |
|---|---|
| 19 | Milk products and dishes |
| 191 | Dairy milk (cow, sheep and goat) |
| 19101 | Milk, cow, fluid, regular whole, full fat |
| 19102 | Milk, cow, fluid, regular whole, full fat, fortified |
| 192 | Yoghurt |
| 19207 | Yoghurt, flavoured or added fruit, reduced fat |
| 19208 | Yoghurt, flavoured or added fruit, low fat or skim, sugar sweetened |
| 19209 | Yoghurt, flavoured or added fruit, low fat or skim, intense sweetened |
It is at this level, users will find most of the detail for comparing consumption against dietary guidance. Subdivision of foods below this level becomes impractical and users who want to subdivide by quite different parameters are able to reclassify individual foods themselves to meet their needs.
For a copy of the full classification system, refer to the 2011-13 Australian Health Survey Classification System file.