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Health & Science

Houston Biologist: Put Your Veggies ‘On the Clock’ For Better Nutrition

Compared to animals, plants don't get enough respect. That’s according to Rice University biologist Janet Braam. Her new research shows that common vegetables are even more responsive than previously believed, even after they've been harvested and shipped to the store.


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That’s Conner Clifton, a rather obliging radio intern. He’s eating a baby carrot. But did he eat that carrot at the right time? 

Not the right time of day for Conner. I mean the right time of day for the carrot, the time at which the carrot is most nutritious.

That’s the question Janet Braam raises in her new paper in the journal Current Biology.

“Plants are – they don’t move around, so they look like they’re not responding to things that are happening around them but actually they are very responsive and active: they can sense wind; they can sense light; they can sense temperature.”

In a previous experiment, Braam showed that some plants, like animals, have internal body clocks that react to light and dark. 

And that internal plant clock has a role in regulating the rise and fall of chemicals that fight off insects.

Does your salad know what time it is?

In the new experiment, Bramm and her lab partners at Rice looked at edible plants like cabbage, lettuce, carrots and blueberries.

They used light and dark cycles to manipulate the circadian clocks in the fruits and veggies, to see if they could adjust the levels of insect-fighting chemicals. They could.

Not only that, they found that the process continues even after the cabbage is cut, the blueberries picked, and carrots pulled from the ground.

Now this might all be just academic, except for the fact that the insect-fighting chemicals are also good for humans to eat.

That’s because they contain cancer-fighting compounds.

“There may be ways to store our vegetables in a way that can enhance nutritional quality. If we can use simple light-dark signals, simple light-dark changes in storage, to get these post-harvest vegetables and fruits to accumulate more nutritional components and chemicals, then it’s a way to optimize the amount of nutrition you get from your vegetables.”

It’s not hard to imagine some sort of technology to take advantage of this discovery, like a produce drawer with lights that switch on and off with a timer.

“And then you get a signal that this is the time to eat it, or cook it, or freeze it, so you can trap that nutritional quality.”

But Braam says more research is needed, and inventing such technologies is up to others.

And she wouldn’t comment on how soon farmer’s markets will start advertising produce whose internal clocks have been tenderly calibrated for maximum nutrition. 

undergraduate researcher Zhengji Sheng
Rice University undergraduate researcher Zhengji “Jim” Sheng prepares to place samples of lettuce and caterpillars in a chamber with controlled lighting. The notation DL refers to the dark-light circadian rhythm of the caterpillar. When the circadian clock of the lettuce matches that of the caterpillar, the leaves are less likely to be eaten. [Photo credit: Jeff Fitlow/Rice University]


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