Light Cannot Destroy the Super Powers of Spinach

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Environmental factors such as light and heat can affect the quality of many foods, but U.S. government researchers have found that light actually benefits spinach, keeping it fresh and allowing it to continue to retain vitamin quality.

Supermarkets often display fresh lettuce in clear plastic bags or containers in a produce case set at around 39 degrees. In some grocers, fluorescent lights shine on the bags 24 hours a day. Gene Lester of the U.S. Department of Agriculture’s Agricultural Research Service decided (while doing some personal shopping) to test the leaves to see if the lighted storage had any effect on nutritional quality.

His team of researchers kept fresh spinach leaves under either continuous light or continuous darkness for three to nine days. The spinach kept under the lights even for just three days had significantly higher levels of vitamins C, K, E, and folate. They were also more colorful, reflecting high amounts of carotenoids lutein and zeaxanthin. The leaves stored in the dark actually lost nutrients.

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Lester said that he shouldn’t have found the results surprising. The leaves of plants use light from the sun as energy to make fuel. The green pigment chlorophyll is the primary pigment involved. Even when picked, the leafy greens will continue to photosynthesize “as long as there is moisture in the leaves and as long as there is gas exchange and light.”

Spinach is particularly high in chlorophyll, as are most leafy greens including kale, collards, and romaine lettuce. Other green vegetables would also likely benefit from lighted storage conditions, such as broccoli, bell peppers, asparagus, Brussels sprouts, and green beans.

The researchers noted that one of the carotenoids in spinach did not increase during the study – betacarotene – so orange fruits and vegetables may not receive the same benefits from light.

Keep in mind, thought, that fresh leafy greens shouldn’t be kept longer than three days, even in these conditions, because they will begin to wilt and lose both aesthetic and taste quality.

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