Dietary Data
I’m working with UK Biobank dietary data and would like to know:
- How to access the UK Nutrient Database (UKNDB) food composition tables.
- How to find the portion sizes used for nutrient calculations.
The questionnaire guide references Food Portion Sizes, 2nd ed., 1993 (MAFF), but it does not specify which values were used. Any guidance would be much appreciated!
Comments
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Hi Reihane,
You can access the UKNDB data via the UK Data Service https://ukdataservice.ac.uk/.
Once registered you will be able to download the data in the format that you prefer (e.g. Stata, csv etc). You will need to cite the UK Data Service in any publication where the data is used but you'll be told that when registering.
The data in Category 100117 was calculated by an external research group based at the Cancer Epidemiology Unit of the University of Oxford (Perez - Cornago A. Eur J Nutr. 2021; 60(7): 4019-4030. https://doi.org/10.1007/s00394-021-02558-4.)
Regarding portion sizes, each food item is given its weight in grams - this is the item portion size multiplied by the number of portions consumed and is the value that gets used with food codes to determine nutrient composition. It was considered by the team to be more useful than portion size alone.
Each food item is derived from the answers to the diet questionnaire. Sometimes it is a simple mapping (for example, apple in the diet questionnaire maps directly to apple as a food item) and sometimes it is more complex (if, for example, someone drinks 4 mugs of black tea, and they've answered that they varied between both caffeinated and decaffeinated tea, then they'll be assigned 2 mugs of caffeinated black tea and 2 mugs of decaffeinated black tea).
Useful information regarding portion sizes can be found in the supplementary tables of the paper referenced above.
I hope this is helpful.
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