The nutrient content of kale has been measured by food scientists for decades and has allowed them to recognize a disturbing trend: the nutrient content in produce such as kale tends to be on the decline. Compared to 1950, kale has about 57% less riboflavin, 48% less calcium, 33% less iron, 22% less phosphorus, and 10% less vitamin C. Though these kale-specific results are not statistically significant, they are part of a larger trend of declining nutrients in fruits and vegetables. To learn more about this trend and what you can do, check out our article on nutrient decline.
Kale: Nutrient Change Data
In the table below we provide the nutritional content of kale from 1950 and 1999. The 1950 values for kale are adjusted for water content — a sample with more water will bias the results. These nutrient measures are based on just a few data points and none of the apparent differences are statistically different, however as a group, they suggest that nutrition has decreased in smaller garden produce.
Nutrient Change In Kale
*The 1950 data is adjusted for water content.
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The graphs used to present changes in nutrition in garden crops here on the Traditional Foods website, including change in kale, can be redistributed for noncommercial use with a link to this particular page or to our more general article : nutrient decline in garden crops.
The historical values on the nutritional content of food has been collected and made available by the USDA. It was also examined by Davis, Epp, and Riordan whose work we describe on this site. We adjusted the 1950 kale nutritional content so that the water content of the 1950 and 1999 samples would be the same, as did Davis, Epp, and Riordan.
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