Supermarket lighting enhances nutrient level of fresh spinach

Gene Lester, Donald J. Makus, and D. Mark Hodges note that fresh spinach is a nutritional powerhouse, packed with vitamin C, vitamin E, folate (a B vitamin), and healthful carotenoid antioxidants. Supermarkets often display fresh spinach in clear plastic containers at around 39 degrees Fahrenheit in showcases that may be exposed to fluorescent light 24 hours a day. Lester, Makus, and Hodges wondered how this continuous light exposure might affect spinach's nutritional value.

The scientists exposed fresh spinach leaves to continuous light or darkness during simulated retail storage conditions for three to nine days. Spinach stored in light for as little as three days had significantly higher levels of vitamins C, K, E, and folate. They also had higher levels of the healthful carotenoids (plant pigments) lutein and zeaxanthin. During continuous light exposure after nine days, levels of folate increased between 84 and 100 percent, for instance. Levels of vitamin K increased between 50 and 100 percent, depending on the spinach variety tested. By contrast, spinach leaves stored under continuous darkness tended to have declining or unchanged levels of nutrients, the scientists say.