The study tested so-called Golden Rice against both spinach and supplements in providing vitamin A to 68 six- to eight-year-olds in China.

Researchers found that the rice was as effective as the capsules in giving kids a boost of vitamin A, based on blood tests taken over three weeks.

And it worked better than the natural beta-carotene in spinach, the researchers report in the American Journal of Clinical Nutrition.

Normally, rice plants produce beta-carotene - a precursor to vitamin A - in their green parts, but not the grain that people eat. Golden Rice is genetically engineered to produce beta-carotene in the edible part of the plant.

The product has been around for years, but it has yet to come into real-world use for a number of reasons. Because it's genetically modified, it has faced opposition from environmental groups and others.

There have also been questions about how efficiently the beta-carotene in Golden Rice can be converted into vitamin A, especially in children.

But the new study suggests the rice works as well as synthetic beta-carotene given in capsules, according to lead researcher Guangwen Tang, of Tufts University in Boston.

"While further study is needed, our results suggest that Golden Rice could be one useful way to combat vitamin A deficiency in areas where rice is a staple food crop and where vitamin A deficiency is still common," Tang said in an email.

As many as 250 million children worldwide are vitamin A deficient, according to the World Health Organization.

Vitamin A deficiency can cause blindness and, because it dampens immune system function, leaves children more vulnerable to becoming severely ill from infections.

If all children in deprived areas were given enough vitamin A, up to 2.7 million deaths could be prevented each year, according to Tang's team.

"We know vitamin A deficiency is a huge problem," said Keith P. West, a professor of infant and child nutrition at Johns Hopkins Bloomberg School of Public Health in Baltimore.

"We know that some children are going to die who shouldn't have died, because of this one nutrient," said West, who was not involved in the study.

He said the findings are encouraging. "The beta-carotene is absorbed at a level that should affect the vitamin A status of young children," West said.

NOT A ‘PANACEA'

Golden Rice has been held up as a relatively cheap and simple way to provide vitamin A to children in countries where rice is already a staple, including China and many other Asian countries.

Based on the current findings, Tang's team says a 100- to 150-gram bowl of Golden Rice (3.5 to 5 ounces) should give children about 60 percent of the daily vitamin A they need.

But West said there are many issues beyond whether the beta-carotene in Golden Rice is absorbed.

As a genetically modified food, it has to face regulatory hurdles. It also has to be "grown by and accepted by different cultures," West said. And of course, young children have to be convinced to eat it.

The issue of cultural acceptance is not unique to Golden Rice, West pointed out. But, he said, it underscores the fact that no single food is a "panacea."

There are other "biofortified" foods being studied for combating vitamin A deficiency, including ones conventionally bred to be rich in beta-carotene.

West and his colleagues are beginning a study of "orange maize" in rural villages in Zambia - a country where vitamin A deficiency is common and white corn is a dietary staple.

Research has already suggested that the beta-carotene in the bright-orange corn is converted to vitamin A in the body at a higher rate than the beta-carotene found naturally in vegetables like spinach and carrots.

West noted that UNICEF has a program to give young children vitamin A capsules twice a year (one capsule is good for a six-month supply of the vitamin).

But only some countries with widespread vitamin A deficiency take part in the program, and UNICEF considers "diversifying" diets and fortifying already commonly-eaten foods to be key to combating vitamin A deficiency.

In wealthy countries, people may take food fortification for granted, West pointed out. But in developing countries, there may be no systems in place to provide such foods, or the costs may be out of reach for the poor.

A range of foods naturally contain vitamin A or vitamin A precursors - from liver, fish oil and eggs to spinach, carrots, mango and red peppers. But again, West noted, those foods may either be locally unavailable, depend on season, or be priced beyond what most families in developing nations can afford.

SOURCE: bit.ly/PYRPv7 American Journal of Clinical Nutrition, online August 1, 2012.

• A Permanent Economic Emergency