What do the traditional Maori diet, autumn leaves, and red wine have in common? That's what three very different scientists from Auckland University have begun to piece together. They all share a common interest - the colour red. They've shed light on why plants could help us live longer and healthier by solving a mystery that has puzzled botanists for centuries - why on earth do leaves turn red? Their research has not only solved the mystery but also revealed that when it comes to human health red is the new green.

TRANSCRIPT

Narration
The colour red... it's the colour of danger...the colour of love... it means stop...look at me...eat me.

But here in New Zealand, red is the colour that has brought three very different scientists together.

Botanist Kevin Gould, nutritionist Lynne Ferguson, and chemist Paul Kilmartin are in Rotorua to answer one question...

When it comes to health, is red the new green?

It all started several years ago with a simple botanical conundrum - why leaves turn red.

Kevin Gould
Believe it or not people have looked at red leaves for over a century and nobody knows why leaves turn red.

Narration
The germ of an idea came from an experiment suggesting that red wine was good for you because it was full of antioxidants.

Jonica Newby, reporter
Well Paul here has agreed to be a human guinea pig, and have his antioxidant levels tested while drinking red wine, and so he doesn't feel lonely, I'm going to join him - cheers.

Narration
We're testing chemist Paul Kimlmartin's blood before he drinks anything.

Jonica Newby, reporter
You ready?

Narration
And again in 2 hours to see how many antioxidants from the wine make it into the body.

Paul Kilmartin
We wanted to see do the anti-oxidants carry through into the blood and give some benefit to human healt.

Narration
More on that later.

Meanwhile it was the antioxidants in red wine that gave botantist, Kevin Gould, an idea about red leaves.

He's taking me to Rangitoto Island, an extinct volcano just off Auckland to test his theory.

We've got a half hour trek up the volcano to get to the plants.

Jonica Newby, reporter
So how did you go from humans drinking red wine to plants?

Kevin Gould
It sounds a bit strange I guess but you know red wine is believed to have very potent anti-oxidant properties and we have lots and lots of plants that produce red leaves and I wondered hey maybe these red pigments do the same thing in plants as they do in humans.

Jonica Newby, reporter
So something in it for the plant.

Kevin Gould
There might be.

Narration
Until now the vast range of situations that cause plants to turn red has defied a single explanation.

Kevin Gould
Well plants go red when they're droughted, when they experience freezing temperatures or really high temperatures, when they're flooded, when they get high ultra violet radiation ... when they're eaten by an animal

Narration
Here on the barren basaltic rock of Rangitoto we're looking for a primitive plant that experiences all these stresses.

Kevin Gould
So there's a patch of liverwort just around here... 470 million years old.

Jonica Newby, reporter
Oh really?

Kevin Gould
And it's red.

Jonica Newby, reporter
That must be one of the most ancient plants then.

Kevin Gould
It's absolutely the first plant to colonise the earth yeah.

Narration
But these primitive plants aren't always red, in less extreme conditions they can be green.

Kevin Gould
In this sheltered sort of gully here there's patches of the very same species but it's green.

Narration
This gave Kevin the idea for his first experiment.

Kevin Gould
In essence it's a kind of stressometer what I thought we'd do today is compared green populations of liverworts with red populations of liverworts.

Narration
We're measuring how healthy the different populations of liverwort are under stressful conditions.

Kevin Gould
Well the data are really conclusive. What they said is the red plants are much better able to withstand harsh stressful environments than the green plants

Narration
So if you're a stressed out plant it seems you're better red than dead. But why?

Kevin Gould
Almost all these stresses that a plant can encounter; drought, high temperatures, low temperatures, ultra violet radiation all produce free radicals

Narration
Free radicals are atoms or molecules that have lost an electron.

Kevin Gould
Electrons like to spin around in pairs and if there isn't a pair of electrons they become like jilted lovers. They're out for revenge and they're desperate to snatch electrons from anywhere they can see possible including the tissues in your body and that can lead to cancers and other degenerative ailments.

Narration
Antioxidants are natures defence force, able to mop up dangerous free radicals.

Kevin suspected that the red pigment in plants was a powerful antioxidant protecting it from free radicals.

To be sure, Kevin put his hunch to the test.

His assistant is attacking green and red leaves of the same species.

Kevin Gould
He's going to stab it with a needle.

Narration
Stabbing the leaves produces free radicals.

Kevin Gould
It's going to fluoresce green when free radicals are produced.
I'll flick it over to fluorescence and that's what we've got. This is your leaf tissue. Here are the cells. Here's the wound, here's the stab wound that James has punctured and the green fluorescence is a free radical that has been produced simply as a result of him piercing the leaf.

Narration
Kevin was able to follow the green fluorescence over time. As it darkens the free radicals are being mopped up.

Jonica Newby, reporter
What did you find?

Kevin Gould
The red leaves sponged them up much, much faster than the green leaves

Narration
In fact the red leaves got rid of the free radicals 10 times faster than the green.

Kevin had found the solution to the red leaf mystery.

He discovered whenever a plant needs extra protection they produce one of nature's most potent antioxidants - which just happen to be red.

Kevin Gould
The secret ingredient is a red pigment and it's called anthocyanin and you might not have heard perhaps of the molecule anthocyanin but you're certainly aware of the compound. Anthocyanin causes red in plums and apples and the purples in blueberries and it's anthocyanins that cause the red colour in red wine.

Narration
So will the anthocyanins have the same protective effect in people as they do in plants?

Jonica Newby, reporter
Well we're 3 bottles down and I don't know what it's doing to my antioxidants but we're all feeling pretty good.

Narration
It's time for Paul's second blood test.

Paul Kilmartin
It's two hours since having the wine and we're ready to see have the antioxidants increased or not.

Narration
We'll find out the results soon.

Meanwhile Kevin's work on plants had an unexpected flow on effect when he met nutritionist Lynne Ferguson two years ago.

Lynne was trying to solve what seemed, at the time, to be an unrelated puzzle.

Lynne Ferguson
For many years it's been observed that the Maori people have had very low colon cancer rates. New Zealand Europeans are the highest in the world and yet the Maori have been traditionally amongst the, you know, the lowest of the groups.

Narration
But in recent years colon cancer in the Maori population has soared so Lynne suspected it wasn't genetic but something to do with the traditional diet.

Then while giving a talk on Maori foods Lynne met Kevin.

Lynne Ferguson
I didn't know anything about anthocyanins. I had no clues about the colour but as I was finishing my talk and starting to walk away Kevin came in and spoke to me and he said I'm sure it's because of the anthocyanins

Kevin Gould
While she was talking it occurred to me that well a lot of these things are red.

Narration
Could it be the anthocyanins in traditional foods were protecting the Maori from bowel cancer?

Lynne decided to test the theory using a mainstay of the Maori diet.

Jonica Newby, reporter
These look interesting, what are these?

Lynne Ferguson
They're sweet potato, but the Maori call them kumara.Um.. they're quite a sweet starch sauce, but have got quite a number of interesting properties, but particularly the ones that have got the reddish colour in the middle. That's not a particularly good one, this one he's been cutting here is much better, you can see much more of a deep reddish streak through them.

Jonica Newby, reporter
Oh yeah it's full of red. And this is the good stuff is it?

Lynne Ferguson
That's the red pigment that's really got the high anti-oxidant properties.

Narration
These are the anthocyanins.

Jonica Newby, reporter
So you took these into the lab

Lynne Ferguson
We wanted to see if they might play the same sort of protective role in animals or in humans that they can do in plants, so we've taken them into the lab and done a number of tests.

Narration
Lynne tested the kumera on mice with a predisposition to bowel cancer.

She fed half of them a regular diet and half of them a diet enriched with kumera.

The results were staggering.

Lynne Ferguson
Okay well here's a gut of a mouse that's likely to develop colon cancer and you can see it's a bit of a mess. We've got a very irregular sort of pattern. Now that's not cancer yet but it's highly likely to develop cancer. Here we've got the gut of a mouse that's been fed kumara and you can see it looks quite different. You've got a very regular sort of pattern. This is what a gut should look like.

Jonica Newby, reporter
So what does this mean? Does this mean the kumara actually is protecting against the cancer?

Lynne Ferguson
Well it's certainly protecting against these early stages in this particular model so if this, if it does this in humans this is really good news for us.

Narration
Free radicals in humans have been implicated in everything from premature aging, to cancer and even dementia.

Anthocyanin is four times more potent against free radicals than the more famous antioxidant, vitamin C.

Kevin Gould
You know for something so fundamental, so academic such as why leaves turn red we've come up with research that can have profound implications for human health. I think it's great.

Narration
But does all this mean it's good news for the red wine drinkers out there?

Jonica Newby, reporter
So two hours in how much have your anti-oxidants gone up?

Paul Kilmartin
About 10% increase.

Jonica Newby, reporter
That's a lot.

Paul Kilmartin
So that is quite significant and that will keep going for a few hours. It will then taper off so maybe we don't need any more wine today.

Narration
And red wine is not the only way to up your anthocyanins.

According to Lynne when it comes to food the message is simple.

Lynne Ferguson
More red. More red wine, more kumera, more red berries, strawberries, raspberries.

Narration
And ironically, the best red food of all is blue...blueberries.

Blueberries have so much anthocyanin they actually appear purple or blue.

But almost all red or purple foods should pack an anthocyanin punch.

Lynne Ferguson
Any of those are going to be useful to you in terms of health, and good to eat and possibly protect against cancer.

Narration
So don't forget to eat your reds, as well as your greens.

Story Contacts

Prof. Kevin Gould
Botanist
University of Auckland

Professor Lynne Ferguson
Nutritionist
University of Auckland

Dr Paul Kilmartin
University of Auckland

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