Nutrient levels in food range widely, thus making a mockery of food tables. An example of this is potatoes grown in Norway (didn't know they did grow them until I read the study). What they found was:
- That same potato variety varied from 8.4 - 18.7 mg / 100 g depending on location. To put it another way there is 220% variation in vitamin C content due to farming location
- Different breeds of potatoes had different levels of vitamin C. Breeds had averages of 9 to 19 mg / 100 g. the highest level was more than twice the lower level. (and these are averages, individual samples would add extra variation).
- Furthermore the breeds were affected differently by different locations. Depending on location this variation was approximately 6, 8 or 10 mg / 100 grams.
- Vitamin C levels decreased with storage. They compared fresh potatoes to three month old cool store potatoes. They found that the absoulte lose was approximately 4mg of vitamin C / 100 g. However due to the different starting levels of vitamin C the losses were 36%, 33% and 26%.
Reference: Nordbotten et al Sampling of potatoes to determine Representative values for nutrient content in a national food composition table. Journal of food composition and analysis vol 13 pg 369, 2000.
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