Produce growers are starting to switch from HID lights to energy-efficient LED lights due to cost.
Aside from saving money on energy bills, crops grown under LED lights have tested to include higher nutritional content.
Plant growth and development are a result of how plants respond to stimuli from their environment. Part of this interaction is caused by specific proteins that interact with light wavelength, causing the plant to respond.
Light quantity, quality and duration inform the plant of conditions that contribute to plant productivity and produce quality.
Sensing the important ramifications and commercial applications of the flavor and nutritional benefits of LED light on plants, a number of researchers have conducted in-depth studies that demonstrate the benefits of proper dosage of LED light in specific wavelengths.
For example, a study conducted by Wageningen UR Greenhouse Horticulture studied several tomato varieties with different intensities of light. The study concluded that certain varieties of tomatoes who received extra light from LED grow lights, contained up to twice as much vitamin C as the tomatoes not exposed to the LEDs .
Japanese researchers published a scientific study in 2011, demonstrating increased antioxidant levels in Satsuma mandarin (Citrus unshiu Marc.), Valencia orange (Citrus sinensis Osbeck), and Lisbon lemon (Citrus limon Burm.f.) when exposed to blue light (470nm) .
Vilnius University, located in Lithuania, performed research and found that a pre-harvest LED light treatment remarkably enhanced antioxidant and nutritional properties of certain green vegetables. This result is due to the increased activity of the metabolic system for the protection from a mild photo-oxidative stress.
For example, application of supplemental LED lighting to dill and parsley resulted in the accumulation of vitamin C, carbohydrates and the enhancement of free radical binding activity and the activity of nitrate-reducing enzyme, according to this study from Vilnius University in Lithuania .
Thomas Colquhoun from the University of Florida published a report in 2013, demonstrating that fruit volatile profiles of tomato, strawberry and blueberry can be manipulated with specific light treatments. (Volatiles are the chemicals emitted by a piece fruit that allow you to smell and taste it. These compounds are really important in providing flavor to fruit and vegetables.) 
The University of Florida research team also found that post-harvest food stored under LED lights improved in appearance and flavor.
Additional research on whether LED lights improve flavor and nutrition is ongoing but the results thus far has helped to convince numerous growing operations to switch to LED lights.
-  https://www.wageningenur.nl/en/show/Tomatoes-with-extra-vitamin-C-via-LED-lamps.htm
-  Zhang, L. (2011) “Regulation of carotenoid accumulation and the expression of carotenoid metabolic genes in citrus juice sacs in vitro.” Journal of Experimental Botany, doi:10.1093/jxb/err318.
-  Bliznikas Z. (2012) “Effect of supplementary pre-harvest LED lighting on the antioxidant and nutritional properties of green vegetables.” Acta horticulturae, 939:85-91.
-  Colquhoun, T. (2013) “Light modulation of volatile organic compounds from petunia flowers and select fruits.” Postharvest Biology and Technology, 86:37–44.