Managing the internal clocks of the food that you eat in order to make it healthier? Sounds a bit strange, or perhaps unbelievable? Well, such a practice does seem to have a notable effect on insect resistance, and perhaps human health and product shelf life, according to new research from Rice University and the University of California at Davis.
By manipulating the internal clocks — circadian rhythms — of various vegetables and fruits the researchers were able to increase the plants’ production of various anti-insect compounds, ones which may benefit human health — such as 4-MSO, a known anti-cancer compound.
“Vegetables and fruits don’t die the moment they are harvested,” stated Rice University biologist Janet Braam, the lead researcher of the new study, and a professor and chair of Rice’s Department of Biochemistry and Cell 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.”
For the new work, the researchers simulated day-night cycles of light and dark as a means to control the internal clocks of various vegetables and fruits, including cabbage, blueberries, carrots, and squash. This new research builds upon the team’s 2012 study of the various means by which plants utilize their internal clocks to regulate their anti-insect defenses. “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.”
According to Braam, the idea for the new research was inspired by a conversation that she had with her 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!’ 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.”
Since arabidopsis and cabbage are relatively closely related, the researchers started their work by trying 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.”
By utilizing controlled lighting within a sealed chamber, the researchers found that they “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.”
“We were able to entrain each of them, even the root vegetables,” said lead author Danielle Goodspeed said. According to her and the other researchers “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 stated. “What we have shown is that keeping the internal clock ticking is advantageous with respect to insect resistance and could also yield health benefits.”
With regards to the cabbage, the researchers found that “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.”
The researchers have already begun follow-up research on this subject, which is investigating “whether light and other stimuli, like touch, may be used to enhance pest resistance of food crops.”
“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 said.
Th new research was just published in the journal Current Biology.