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Monday March 6 20006

Traditional NZ foods set antioxidant standards

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Marilyn Head for ABC Science Online

Plants traditionally eaten by Maori people are the world's richest source of antioxidants, New Zealand scientists say.

"Until now blueberries have been regarded as the 'king of the antioxidants', the best source of antioxidants in a Western diet and the standard by which they're measured," Associate Professor Kevin Gould, of the University of Otago, said.

"But almost half the plants we tested had concentrations many times higher."

Associate Professor Gould measured levels in both native and introduced plants.

Puha, a plant similar to watercress and still commonly eaten by Maori people, has over three times the concentration of antioxidants of blueberries.

New Zealand honeysuckle has 10 times more.

But the fruit of the Syzygium maire or swamp maire tops the lot, with 18 times the concentration.

Associate Professor Gould says the study, published in the New Zealand Journal of Botany, opens up several exciting avenues for further research.

"It may account for the low incidence of non-infectious disease in pre-European Maori," he said.

"Even now Maori are less at risk from colon and rectal cancers than New Zealanders of European descent.

"But it may also reflect the way New Zealand plants are responding to global warming and other environmental stresses."

Plants are particularly susceptible to stress from too much ultraviolet (UV) radiation.

New Zealand has one of the highest levels of UV radiation in the world because of the hole in the ozone layer above Antarctica.

All organisms produce free radicals when they are stressed.

Normally the organism can deal with them by producing its own antioxidants to mop up them up.

But too many antioxidants can cause damage.

A free radical is an unstable molecule that behaves irrationally," Associate Professor Gould said.

"It's a bit like a jilted lover, bent on revenge, wanting to attack the first thing it sees.

"It's unstable because it's lacking an electron, or it's got too many, so it just wants to grab one from anywhere, including the tissue from your lung or your bowels."

Finding plants with such high concentrations of antioxidants may prove doubly beneficial, the researchers say.

They are potentially rich sources of dietary antioxidants and could provide a better understanding of how plants respond to environmental stress.


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