Broccoli Still Packs Nutritional Punch

While some reports have suggested a decline in the nutritional quality of food supplies, mineral levels in new varieties of broccoli have not decreased since 1975, according to new research in the November-December issue of Crop Science. The vegetable contains the same levels of calcium, copper, iron, magnesium, potassium, and other minerals that have made it a healthy staple of American diets for decades.
"For broccoli cultivars grown during the past 35 years, when hybrids became the standard cultivar, evidence indicates that mineral concentrations remain unchanged," says one of the study’s authors, Mark Farnham, a USDA-ARS geneticist with the U.S. Vegetable Laboratory in Charleston, SC. "As broccoli breeders continue to improve this crop in the future, data from this study can serve as a very useful guide for helping breeders understand the variation in mineral concentrations they should expect among their breeding stocks, and provide a realistic baseline that should be maintained as other characteristics are manipulated in the future."
To reach those conclusions, Farnham evaluated the mineral content of 14 broccoli cultivars with two other scientists: USDA-ARS plant physiologist and Baylor College of Medicine professor, Michael Grusak, and Clemson University scientist, Anthony Keinath. After growing the 14 cultivars in two field trials in 2008 and 2009, and testing the florets, the team found that despite being released to growers over a span of more than 50 years, the varieties differed little in nutritional quality over time.
More specifically, broccoli florets in the study were tested for levels of calcium, copper, iron, potassium, magnesium, manganese, molybdenum, sodium, phosphorous, sulfur and zinc. Results indicated significant differences between cultivars in floret concentrations of calcium, copper, iron, magnesium, sodium, phosphorous and zinc, but not of potassium, manganese, molybdenum or sulfur. At the same time, there was no clear relationship between mineral concentration and release year.
"Our studies show that not much has changed in terms of mineral content in the last 35 years in a crop that has undergone significant improvement from a quality standpoint and that was not widely consumed in the United States before the 1960s," Farnham says.

Source:

Summarized from a USDA-ARS news release and the research article:
Mineral Concentration of Broccoli Florets in Relation to Year of Cultivar Release
Mark W. Farnham, Anthony P. Keinath, and Michael A. Grusak
Crop Science
https://www.crops.org/publications/cs/abstracts/51/6/2721