Go bananas for vitamin A

Bananas genetically modified to beef up their vitamin and iron content have been unveiled by Australian researchers.

The problem that Queensland University of Technology's James Dale and his colleagues were trying to address is chronic vitamin A and iron deficiencies amongst the populations of some countries, Uganda among them, where bananas are a food staple.

"People there might cook and eat up to a kilo of bananas a day," says Dale.

"But the native fruit can be very poor sources of certain micronutrients including vitamin A, so people eating them frequently can become deficient, leading to a range of diseases including blindness."

The approach taken by the team was to produce a banana rich in the chemical precursor for vitamin A, an orange-coloured molecule called beta-carotene. When eaten, this beta-carotene is split into two vitamin A molecules in the body, in proportion to a person's vitamin A requirements, so there is no risk of vitamin A poisoning.

To do this, the team borrowed genes from other banana strains, including the Asupina from Papua New Guinea, which, owing to the presence of an altered form of a gene called phytoene synthase, naturally contain much higher levels of beta-carotene.

At the same time, to pep up the iron content of the fruit to help consumers fend off anaemia, the researchers increased the expression of a molecule called ferritin, which works like a molecular cage capable of trapping iron. By also increasing the mobilisation of iron in the plant through other genetic manipulations, the result is far more iron finding its way into the fruit, where it lodges in the ferritin until eaten.

Dale doesn't know if his modified bananas still taste okay - or at least he's not admitting to a sly bite or two - but he's about to find out thanks to the granting of a license to commence a human feeding shortly.

Meanwhile, data from gerbils, which metabolise beta-carotene and vitamin A very similarly to humans, suggests that the fruits pack an effective nutritional vitamin punch. But are the bananas safe, and could there be any risks?

Banana plants don't release pollen and generally need to be propagated by taking cuttings, so environmental control of the modified strains shouldn't be a problem. As to the chemistry of the fruits themselves, having tested them with chromatography techniques, Dale is confident that the chemical make up has not been altered beyond the enhancement of iron and beta-carotene.

But will it work? The proof really will be in the eating...