Are we sacrificing nutrition for convenience when we buy prewashed salad greens?
They’ve become wildly popular in recent years. It’s so easy to open the bag and have greens ready to be tossed into a salad. No more washing. No more drying with paper towels or using “salad spinners.”
They’ve turned healthy food into convenience food.
But it does come with a downside. Studies have found that prewashing and chopping of commercially packaged greens accelerates nutrient loss. The vitamins that are stripped out the fastest are water-soluble ones. They include vitamins B and C, and carotenoids.1
The washing causes immediate vitamin C loss. The mechanical chopping of the leaves increases this loss.2 3
Folate (vitamin B9): Ohio State researchers found that washed spinach retained only 53% of its folate (vitamin B9) after eight days.
A recent Norwegian study shows that chopped, washed lettuce loses up to 40% of its folate within just four hours.4
Vitamin C: Researchers at the University of Edinburgh revealed that by the time you eat prewashed lettuce, 59% of its vitamin C is lost.5
The same study, published in the journal Food Chemistry, found that mature spinach lost 80% of its vitamin C. Baby spinach lost up to 45%.
Carotenoids: The Ohio State study found that prewashed spinach retained only 54% of its carotenoids after eight days.
The University of Edinburgh study found that chopping greens also increased the content of an anti-nutrient called oxalate (oxalic acid). It binds to minerals in the gut and can stop the body from absorbing them. This makes the greens less nutritious.6
Get the Most Nutrients from Your Greens
Prewashed greens are still super-healthy, even with the vitamin loss caused by washing and chopping.
But if you want maximum nutrition go for whole—not chopped—greens. And buy greens that are not prewashed.
If you don’t want to give up the convenience of prewashed, be sure to check the sell-by date on the bag. The fresher the better.
And whether you prewashed or not, go for organic greens. They are higher in nutrition than conventionally grown varieties. And more important, they contain no harmful pesticide residues
One more thing… Farmers markets are a great place to get fresh, organic greens. If possible, buy them the day you are going to eat them.
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References:
1 https://www.nytimes.com/2017/11/03/well/eat/do-prepackaged-salad-greens-lose-their-nutrients.html?em_pos=small&emc=edit_hh_20171103&nl=well&nl_art=2&nlid=79817619&ref=headline&te=1
2 http://www.sciencedirect.com/science/article/pii/S0308814617306556
3 http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.2004.tb09919.x/full
4 http://www.tandfonline.com/doi/full/10.1080/17482970701284510
5 http://www.sciencedirect.com/science/article/pii/S0308814617306556
6 https://www.healthline.com/nutrition/oxalate-good-or-bad#section3