Nutrient-boosted foods protect against blindness

Editorial: "Nutrient-boosted Golden Rice should be embraced"

THERE'S a new weapon in the battle against blindness, and it's bright orange. A sweet potato bred naturally to contain loads more beta carotene than its traditional counterparts has helped stave off vitamin A deficiency in thousands of Ugandans. The announcement comes as other results confirm that beta-carotene-packed genetically modified rice can also boost dietary vitamin A effectively. Beta carotene is converted into vitamin A in the body.

About half a million children in Africa and Asia go blind every year because their diet contains too little vitamin A, which is vital for vision and the immune system. Of those who lose their sight, two-thirds die within months.

Aid agencies currently treat the deficiency by giving children high-dose capsules of vitamin A twice a year, but supplying the missing vitamin through locally grown food would be more practical and sustainable.

Enter the sweet potato. The orange flesh of a standard sweet potato betrays its beta-carotene content - the same stuff responsible for the carrot's hue. The new strain has four to six times the beta-carotene of an average sweet potato.

A two-year project involving 10,000 households in Uganda found that vitamin A intake doubled in women and in children aged 6 to 35 months who ate the improved sweet potatoes compared with families that continued eating regular varieties. By the end of the project almost 90 per cent of the kids eating the new strain had escaped vitamin A deficiency, compared with just 50 per cent in a control group.

"There's great potential for these potatoes," says Christine Hotz of the International Food Policy Research Institute in Washington DC, who headed the Ugandan project (Journal of Nutrition, DOI: 10.3945/jn.111.151829).

More controversial than the naturally bred sweet potatoes is Golden Rice - genetically engineered to contain 30 micrograms of beta-carotene per gram. Ordinary rice has none.

Critics had claimed that the rice is impractical. According to calculations by Greenpeace, people would need to eat huge amounts - as much as 18 kilograms of cooked rice a day - to obtain enough vitamin A.

A study involving 68 Chinese children demolishes the criticism. Guangwen Tang of Tufts University in Boston, Massachusetts, and colleagues have demonstrated that just 100 to 150 grams of the rice - about half the children's daily intake - provided 60 per cent of the recommended daily intake of vitamin A.

The children were given beta-carotene either in the rice, in pure form in oil, or in spinach. All the beta carotene they received contained isotopes enabling any vitamin A made from it to be distinguished from vitamin A that was already circulating in their blood.

Analyses showed that it took 2.3 grams of beta-carotene derived from rice to make a single gram of vitamin A - only marginally less efficient than making it from oil, which took 2 grams (American Journal of Clinical Nutrition, DOI: 10.3945/ajcn.111.030775).

"The conversion rate can't get better than that," says Adrian Dubock, project manager for the Golden Rice Project. He hopes that Golden Rice will eventually become widely available, despite objections. "It's been a long haul, but the new results give us confidence we're on the right track," he says.

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