People tend to frown on frozen vegetables and fruits, but fresh isn't always best. In a paper published in the June 2017 issue of the Journal of Food Composition and Analysis, researchers measured the nutritional content (vitamin C, vitamin A, and folate) of three types of produce--fresh, frozen, and fresh-stored (purchased fresh and then refrigerated for 5 days)--over a 2 year span. Items examined were broccoli, green beans, blueberries, and strawberries.
In the majority of cases, vitamin content did not vary among the three categories, but when there were significant differences, frozen fruits and veggies bested fresh-stored versions more often than not. While fresh produce is typically most nutrient-dense at harvest, nutrients degrade during shipping, while foods sit on store shelves and until we retrieve the items from our refrigerators. On the flipside, the frozen counterparts are flash-frozen almost immediately after harvest, which locks in nutrients and keeps them from degrading.
The takeaway? Buying fresh fruits and veggies from local sources and eating them immediately is probably still best, but convenient and budget-friendly subzero produce is a nutritious fallback. Besides, people who work subzero fruits and vegetables into their diets have been shown to benefit from higher produce intakes overall than those who shun them, and the former also have higher intakes of essential nutrients like potassium and calcium.