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Give your vegetables 12 hours of light and 12 hours of night for antioxidants

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Almost everybody knows vegetables, fruits, and other plants can tell night from day. But did you know that when you give vegetables and fruits daylight and dark hours, just like people have when they sleep, the plants keep more of their antioxidants and dense nutrition? Sacramento and Davis scientists are studying the way vegetables can tell time by their circadian clocks. If you want more antioxidants in your vegetables, let those plants know when it's day and when it' night. For example, you can give your vegetables and fruits 12 hours of daylight and 12 hours of darkness.

Researchers locally at the University of California, Davis and also at Rice University have found that by keeping produce in day/night conditions, rather than in a dark box, the produce takes on more healthful properties with more antioxidants saved in the plant for your nourishment.

If your vegetables and fruits need refrigeration, keep them in the cooler, for example if your vegetables are cut rather than in a planter. Tomatoes, onions, most root vegetables, bananas, and lemons or potatoes and avocados don't have to be always in the refrigerator if there are not cuts on them and if they're not peeled or in other ways always need to be kept cold. But refrigerate what needs to be kept cold. But some vegetables do need to be in the cooler 24 hours a day.

Researchers are altering the biological clock of vegetables to see why a salad knows what time it is

Vegetables want to discern day from night in cycles. Biologists from Sacramento and Davis from the University of California, Davis and at Rice University have found there may be potential health benefits to storing fresh produce under day-night cycles of light. You may wish to check out the article, "Want More Antioxidants? Let Your Vegetables Know When It's Night."

Don't store plant foods day and night in bright light, and don't store them day and night in the dark, or they'll lose their nutrients. They want wake and sleep cycles just like humans. Vegetables make cancer-fighting antioxidants at certain times of the clock for days after they're harvested.

In a new study published the week of June 20, 2013 in the journal Current Biology, researchers used lighting to alter the circadian rhythms of cabbage, lettuce, spinach, zucchini, carrots, sweet potatoes and blueberries. The scientists showed how manipulation of circadian rhythms caused cabbage to produce more phytochemicals, including antioxidants. Locally, UC Davis maintains a Vegetable Research and Information Center.

If your salad knows what time it is, then you have a way of managing vegetables’ ‘internal clocks’ post-harvest that could have health benefits. Does your salad know what time it is? It may be healthier for you if it does, according to new research from Rice University and the University of California at Davis.

“Vegetables and fruits don’t die the moment they are harvested,” explains Rice biologist Janet Braam, in the June 20, 2013 news release, "Does your salad know what time it is?" Braam is the lead researcher on a new study this week in the journal Current Biology. “They respond to their environment for days, and we found we could use light to coax them to make more cancer-fighting antioxidants at certain times of day.” Braam is professor and chair of Rice’s Department of Biochemistry and Cell Biology.

Braam’s team simulated day-night cycles of light and dark to control the internal clocks of fruits and vegetables, including cabbage, carrots, squash and blueberries

The research is a follow-up to her team’s award-winning 2012 study of the ways that plants use their internal circadian clocks to defend themselves from hungry insects. That study found that Arabidopsis thaliana — a widely used model organism for plant studies — begins ramping up production of insect-fighting chemicals a few hours before sunrise, the time that hungry insects begin to feed.

Braam says in the news release that the idea for the new research came from a conversation with her teenage son

“I was telling him about the earlier work on Arabidopsis and insect resistance, and he said, ‘Well, I know what time of day I’ll eat my vegetables.’ Braam said. “That was my ‘aha!’ moment. He was thinking to avoid eating the vegetables when they would be accumulating the anti-insect chemicals, but I knew that some of those chemicals were known to be valuable metabolites for human health, so I decided to try and find out whether vegetables cycle those compounds based on circadian rhythms.”

Vegetables go through jet lag, too and need to reset their internal clocks to the day-night cycle of their new environment

Arabidopsis and cabbage are related, so Braam’s team began their research by attempting to “entrain” the clocks of cabbage in the same way they had Arabidopsis. Entrainment is akin to the process that international travelers go through as they recover from jet lag. After flying to the other side of the globe, travelers often have trouble sleeping until their internal circadian clock resets itself to the day-night cycle in their new locale.

Using controlled lighting in a sealed chamber, Rice graduate student and study lead author Danielle Goodspeed found she could entrain the circadian clocks of postharvest cabbage just as she had those of Arabidopsis in the 2012 study. Following the success with cabbage, Goodspeed and co-authors John Liu and Zhengji Sheng studied spinach, lettuce, zucchini, carrots, sweet potatoes and blueberries.

The storage of vegetables in cold, dark trucks reduces their ability to keep up their daily biorhythms and produce more nutrients for human consumption: Produce needs to be 'entrained' to help them to produce more nutritious micronutrients and phytonutrients

“We were able to entrain each of them, even the root vegetables,” Goodspeed says in the news release. She and Braam explain in the news release that the findings suggest that storing fruits and vegetables in dark trucks, boxes and refrigerators may reduce their ability to keep daily rhythms.

“We cannot yet say whether all-dark or all-light conditions shorten the shelf life of fruits and vegetables,” Braam observes. “What we have shown is that keeping the internal clock ticking is advantageous with respect to insect resistance and could also yield health benefits.”

In the cabbage experiments, Braam, Goodspeed and Rice co-authors John Liu, Zhengji “Jim” Sheng and Wassim Chehab found they could manipulate cabbage leaves to increase their production of anti-insect metabolites at certain times of day. One of these, an antioxidant called glucoraphanin, or 4-MSO, is a known anti-cancer compound that has been previously studied in broccoli and other vegetables.

Can light enhance pest resistance of food crops?

Braam’s team has already begun follow-up research, which is supported by the Bill and Melinda Gates Foundation, into whether light and other stimuli, like touch, may be used to enhance pest resistance of food crops in developing countries. “It’s exciting to think that we may be able to boost the health benefits of our produce simply by changing the way we store it,” Goodspeed explains in the news release.

Additional co-authors include Marta Francisco and Daniel Kliebenstein, both of the University of California at Davis. The National Science Foundation and a 2011 Medical Innovation Award from the Rice University Institute of Bioscience and Bioengineering supported the research. Also, you may want to check out the article, "UC Davis ranks No. 1 in the world for agricultural teaching and research." Or see, "Nutrition Experts Urge Americans to Hold the Line on Weight" and "Couch potatoes no more: Video game will fight obesity."

You also may be interested in check out the news releases, "Preventing the “Freshman 15” via the Web – New study reports process improvements to improve college student weight-related health behaviors (July/August 2013)," and "Do Food Blogs Serve as a Source of Nutritionally Balanced Recipes? An Analysis of Six Popular Food Blogs -- Reported in the Current Issue of the Journal of Nutrition Education and Behavior (November/December 2013)."



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