These are cooking bananas, common in Africa, typically eaten steamed or fried. And that's where the bananas ultimately are headed, if all goes well. They're intended for Uganda, where bananas are a staple food and many people suffer from vitamin A deficiency.

Yet if the experience of similar "biofortified" crops is any guide, this banana faces a path strewn with obstacles and uncertainty.

More than a decade ago, for instance, researchers created a kind of "golden rice" with high levels of beta carotene — and immediately found themselves in the middle of controversy. In the Philippines, anti-biotech activists destroyed a test plot of the genetically engineered grain. When researchers carried out a feeding trial of golden rice in China, using children as subjects, it turned into a national scandal. The researchers were denounced for not disclosing, in all cases, the fact that the new rice was genetically engineered. No government has approved widespread cultivation of golden rice.

The trial in Iowa is not likely to stir up similar controversy. Yet Wendy White, the researcher at Iowa State University who is carrying it out, is reluctant to discuss it. In an e-mail to NPR, she wrote that disclosing details about the study "could preclude me from publishing our findings in a peer-reviewed scientific journal."

Even if, as expected, the Iowa experiment confirms that beta carotene in the bananas does boost vitamin A levels in the volunteers' blood samples, this doesn't mean that the "super banana" really is a solution to the problem of vitamin A deficiency in Uganda.

Many regulatory and practical obstacles remain. For the banana to have any impact at all, governments would have to approve it, farmers would have to grow it, and ordinary people would have to be persuaded to eat orange-tinted bananas.

Even if all that happened, the benefits of eating high-beta-carotene bananas, in a real-world African village, are likely to be subtle. That impact "is a very hard thing to measure," says Erick Boy, a specialist on nutrition at the International Food Policy Research Institute. Boy works with an initiative called HarvestPlus, which is working to create biofortified crops through traditional breeding.

Michael Grusak, a specialist on the nutritional quality of food with the USDA's Agricultural Research Service, is convinced that crops with higher nutritional levels are worth the effort, even if their effects are difficult to measure. "We know that people are not getting enough" crucial nutrients, such as vitamin A and iron, he says. "You have to get more in their mouths and hope for the best after that."

HarvestPlus's biggest success so far is the deep-orange sweet potato, which was introduced in Mozambique and Uganda. That crop requires no regulatory approvals, since it was created by cross-breeding existing varieties, rather than through genetic engineering. This sweet potato also packs a dose of beta carotene several times bigger than what's in the new super banana.

A village-by-village promotional campaign succeeded in persuading farmers and consumers to adopt the orange sweet potato. And according to Boy, scientists are now seeing evidence that people who eat it regularly are, in fact, healthier.

Copyright 2014 NPR.

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Globe-Trotting GMO Bananas Arrive For Their First Test In Iowa