UV Exposure Makes Lettuce Healthier

Scientists at the US Department of Agriculture (USDA) have found a way to nutritionally enhance lettuce: by forcing them to produce their version of suntan lotion. Plants produce powerful flavonoid antioxidants, such as quercetin and cyanidin, when they are exposed to the sun's harmful ultraviolet (UV) rays. These compounds act as the plants' suntan, protecting them from the mutation-causing UV rays. Flavonoids are thought to provide a variety of health benefits to human beings, from fighting cancers to improving brain functions.

The USDA researchers created lettuce plants with increased flavonoid levels by exposing them to ultraviolet light emitting diodes (LEDs). The LED-exposed plants are noticeably redder than their counterparts that only saw white light. While the researchers have yet to quantify this effect, they said that it appears to increase as the intensity of the light increases.

In addition to increasing the amount of flavonoids contained in lettuce leaves, the researchers said that the UV LEDs could help crops grown in winter in the northern climates that receive very little exposure to ultraviolet light. The UV LEDs can also be used to preserve nutrients in fruits and vegetables that have already been harvested. Studies have shown that the peel of a picked apple stays redder for a longer period of time when exposed to ultraviolet light.

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