It depends, of course. The experts cite many, many variables. But perhaps we're asking the wrong questions.
Most frozen produce is picked at peak season and then immediately frozen to retain nutrients and freshness. Fresh produce from faraway places, on the other hand, loses some of its nutrient value while traveling and then sitting on a shelf for days or longer.
But the amount of nutrient loss varies greatly depending on the type of produce, says Jeff Blumberg, professor of nutrition science and policy at Tufts University.
"If you are looking at something like fresh spinach, you are losing up to half the folates after about eight days," Blumberg says.
In general green, leafy vegetables are the most delicate and susceptible to nutrition loss, while vegetables and fruit with a skin or shell (think oranges or squash) are more robust and stay nutritionally intact longer, he says.
That being said, even the green leafy varieties don't lose nutrients across the board, nutritionist Kristen Ciuba says.
"You are not going to lose the fiber or the minerals," Ciuba says.
And even when nutrients are lost, Blumberg adds, some produce, such as spinach, is so rich in folates that "you can afford to lose some of it." Spinach is so nutrition-dense that it's good for you either way you eat it, he says.
And this is generally the story on produce. Get your five to nine servings a day in whatever form you can.
Just make sure, Ciuba says, that the frozen variety doesn't include added salt (vegetables) or added sugar (fruit and berries).
Another thing to keep in mind is to buy whole frozen or fresh fruits and vegetables whenever possible. "Avoid buying chopped, peeled and crushed produce if at all possible," Blumberg says. "Because whenever you accelerate the degradation process, you lose nutrients."
The way produce is prepared actually is more important for nutrition retention than picking the absolute freshest of fresh spinach, for example.
"If you were to boil spinach you would lose much more folate than if you had it sitting in the fridge a few days," Blumberg says, adding that lightly steamed or raw is preferable.
Both Ciuba and Blumberg emphasize that the main message, though, should be to eat more produce, whether fresh or frozen.
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