Ultraviolet LEDs Make Lettuce Healthier

Darker leafy greens are known to be higher in nutrients, including antioxidants, than light colored greens. Using ultraviolet electronic light sources, researchers have recently found a way to make lettuce both darker and redder, potentially laying the foundations for a new, and healthier, form of vegetable consumption.

The red color found on the tips of some lettuce greens act as a protection against ultraviolet (UV) sun-light, which has the ability to damage plant DNA, limiting its nutrients. With this protection, these types of lettuces are able to produce “UV-absorbing polyphenolic compounds,” such as the antioxidant compounds, flavonoids and cyanidin. Antioxidants have been shown in past research to help guard against a wide range of conditions, from heart disease, diabetes, and kidney disease, to cancer.

Light-emitting diodes (LEDs) are based on a semiconductor diode, and can range in brightness from very weak low-intensity red light, to bright visible and ultraviolet light. LEDs consume less energy than normal electrical light sources, but are currently too expensive for general commercial usage.

The current study used low power UVB light (a component of sun-light) LEDs, focused at approximately 10 milliwatts per square meter. Compared to plants only being exposed to white light, after 43 hours, lettuces being exposed to the UVB LEDs were redder, darker, and more packed with nutrients. This effect was especially strong at wavelengths between 282 and 296 nanometers.

This research is the first step for potentially more profound results to come. Further research to confirm the best tactic for UVB LED exposure is currently being performed by Dr. Steven Britz and his team, who says, “we’ve been pleasantly surprised to see how effective the LEDs are, and are now testing how much exposure is required, and whether the light should be pulsed or continuous.” It’s believed by the researchers that the above technique can be used not only to improve nutritional quality of lettuce, but also to “preserve nutrient” in other fruits and vegetables, such as keeping apples redder for longer.

Source: Defeat Diabetes Foundation: Britz, Steven. Morrison, Colleen. Optical Society of America news release. May 2009.

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