Good to Eat

A feeding trial confirms that the provitamin A in “orange maize” is abundantly bioavailable to healthy subjects from porridge prepared using traditional African methods.

Maize is probably the most important food in African diets. Maize consumption per capita is higher in Africa than in any other region. Much of this maize is enjoyed by young and old alike in the form of porridge, the African equivalent of polenta. In many parts of Africa, maize porridge is the first solid food given to children.

New varieties of orange maize with higher amounts of beta-carotene are being developed to provide vitamin A for malnourished people in poorer countries. Thee varieties of maize are being bred using conventional methods. Photo: Robyn Allscheid Stevens.

The HarvestPlus Challenge Program leads a global effort to breed “orange maize” varieties that are rich in beta-carotene, or provitamin A. The beta-carotene is converted to vitamin A by the body when eaten. Given the high prevalence of vitamin A deficiency in Africa, especially in children, using a food as popular as maize to deliver this much-needed nutrient could greatly improve nutrition. Even though white maize is preferred in most of Africa, HarvestPlus research has shown that orange maize is acceptable, especially when its benefits are explained (See Vitamin A Breakthrough in the May 2008 edition of CGIAR eNews). First, however, nutritionists have to answer two questions: How much of the beta-carotene in the maize is retained during processing into porridge? And to what extent is it absorbed from the porridge when eaten? In a 2007 study supported by HarvestPlus, a team led by Wendy White of Iowa State University found that 75% of the beta-carotene was retained in maize porridge that was prepared using traditional African methods — a rate that  is considered very good.

For this and subsequent studies, White used orange maize hybrids rich in beta-carotene that were conventionally bred for HarvestPlus by Torbert Rocheford, who was then at the University of Illinois and now at Purdue University.

In an article recently published in the American Journal of Clinical Nutrition, White was able to answer the second question. Her team found that the beta-carotene in orange maize porridge is indeed bioavailable for conversion into vitamin A in the body. “The conversion rate of the beta-carotene in the biofortified maize to vitamin A was much higher than what had been assumed,” says White, “and higher than from vegetable sources such as spinach and carrots.”

These findings were from a feeding trial with healthy female subjects between the ages of 18 and 30 who consumed traditionally prepared African-style porridges made from both white maize and the new biofortified orange maize. “Now that we know that the beta-carotene from biofortified maize can be effectively used as a source of vitamin A in healthy subjects, we need to evaluate how well the beta-carotene can be utilized in a real world setting.”

“HarvestPlus will conduct further studies in Zambia to see if biofortified maize can improve the vitamin A status of young children,” says Erick Boy, head of nutrition at HarvestPlus. In some parts of Zambia, where HarvestPlus and its partners plan the first release of biofortified maize to take place in 2012, more than half the children under 5 are vitamin A deficient. “It’s possible that, all other things being equal, vitamin A-deficient individuals might absorb even more beta-carotene than healthy individuals in a research setting,” Boy adds.

These advances on the nutrition side of the equation, coupled with recent breakthroughs in maize breeding, mean that orange maize could provide more dietary vitamin A than previously thought possible — and every additional bit of vitamin A in the diet goes a long way toward improving health.

Note: The First Global Conference on Biofortification on 9-11 November 2010 in Washington, DC, was a showcase of the latest progress in research on biofortified maize and other crops.