NPR logo

How Circadian Rhythms Give Vegetables A Healthy Boost

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript
How Circadian Rhythms Give Vegetables A Healthy Boost

Eating And Health

How Circadian Rhythms Give Vegetables A Healthy Boost

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


Now, a far less contentious story about the food that we grow. Scientists are trying to understand the secret life of vegetables, including cabbages, sweet potatoes and leafy greens. Understanding these secrets may help us get more nutritional bang for our buck.

NPR's Allison Aubrey has this report on some new research.

ALLISON AUBREY, BYLINE: It's not news that fresh produce contains lots of healthy compounds or that cruciferous vegetables - like cauliflower and cabbage - are nutritional superstars. But why are these plant chemicals so good for us? And why are they there in the first place? To make sense of this, I have dragged my colleague Dan Charles, who covers agriculture, along with me to the grocery store.

DAN CHARLES, BYLINE: Cabbage, cabbage, cabbage to our left.

AUBREY: All right.

Now, this is kind of hokey. But what I'm asking Dan to do is to pretend that he is a cabbage, to sort of channel his inner cabbage.

You ready, Dan?

CHARLES: I've got my cabbage.

AUBREY: All right, you wear it well.

Now, it turns out that all these good compounds are produced because plants have a pretty tough life out in the field. There are bugs to battle, severe heat and cold. And plants can't just get up and walk away from these challenges.

CHARLES: It's a problem because I'm a cabbage. I've got no hands to slap insects. I can't put up an umbrella to protect myself from the sun. I'm stuck. I'm stuck in the ground.

AUBREY: Yeah, I can see that. Your options are very limited here.

CHARLES: But what I can do is I'm a plant, what I do is I make chemicals. So what I and what my ancestors have done for millennia is to create chemical compounds inside myself to protect myself, to make myself unappetizing to insects, to detoxify the effects of the sun.

AUBREY: Now, it turns out that scientists have discovered that some of these same compounds that help plants defend themselves are good for us too.

PAUL TALALAY: We have studied at great length how these compounds protect human cells.

AUBREY: That's Paul Talalay of Johns Hopkins University. He says that compounds called glucosinolates found in cabbages and other cruciferous vegetables work like little detox agents in our cells.

TALALAY: What the protective effect of these vegetables is, is that they rev up the capacity of cells to dispose of damaging compounds.

AUBREY: In other words, they help our bodies get rid of toxins. Now, as vegetables go from the field to the store to our plates, the levels of these compounds start to fizzle out. So researcher Janet Braam of Rice University had a question: Was there a way for these plants to keep producing these beneficial chemicals after they'd been harvested?

JANET BRAAM: So we went to the grocery store and we just bought some cabbage.

AUBREY: And they tried to recreate some of the conditions in the field, in particular, the light-dark cycle.

BRAAM: So what we knew was that plants can use their circadian clock to turn on defenses at particular times of day.

AUBREY: So they put the cabbages under light for 12 hours a day, followed by 12 hours of darkness.

BRAAM: And sure enough, we found that when we put the plants under light-dark cycles so that they had good circadian rhythms, we found periodic accumulation of those chemicals.

AUBREY: Especially in the afternoon, in the hours before dusk.

BRAAM: Generally, they're significantly higher in the day than they are at night.

AUBREY: Wow. So, really, there's a lot going on there. I mean, who knew, right?

BRAAM: Who knew? Right.


AUBREY: It was as if the plants were still alive even though they're no longer attached to their roots or the earth.

BRAAM: This very much surprised us.



BRAAM: We decided to do the experiment because we thought it was possible that it could work. And yet when it worked, I think we were all taken by surprise.

AUBREY: And they went on to find similar responses in more crops from lettuce and spinach to carrots and blueberries.

Now, Braam is quick to point out that these were just lab experiments. But if the findings carry over into real-life situations, they could have implications for how and when we harvest and store produce.

BRAAM: I think it just opens up the door to many possibilities.

AUBREY: Braam says it might make sense for grocery stores or for us at home to think about storing our produce under light-dark cycles. Or maybe it's time for a vegetable happy hour, eating our produce in the hours before dusk when some of the most beneficial compounds are at their peak.

Allison Aubrey, NPR News.

Copyright © 2013 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.