A study published in the American Journal of Clinical Nutrition has established that ‘orange’ vitamin A maize increases vitamin A storage in the body. This maize has been conventionally bred to have higher levels of beta-carotene, a naturally occurring plant pigment that the body then converts into vitamin A. The participating research centres were from the U.S., Zambia, and the international Maize and Wheat Improvement Centre – CIMMYT. The study was supported by HarvestPlus, a global effort to improve nutrition and public health by developing and deploying staple food crops that are rich in vitamins and minerals. HarvestPlus is part of the Consultative Group for International Agricultural Research (CGIAR).
Lack of sufficient vitamin A blinds up to 500,000 children annually and increases the risk of death from disease (such as diarrhoea in children). Vitamin A deficiency is widely prevalent in sub-Saharan Africa. In many African countries, people eat large amounts of staple foods like cassava or maize. However, white maize and cassava provide no beta-carotene. Switching to orange maize, which is rich in beta-carotene, could potentially provide maize-dependent populations with up to half their daily vitamin A needs.
In the controlled efficacy study, children from the Eastern Province of Zambia were randomly assigned to three feeding groups and received either white maize, orange maize, or a daily vitamin A supplement. After three months, the groups that received either the orange maize or vitamin A supplements both showed significant increases in their total body stores of vitamin A, while no changes were observed in the group that received white maize.
The scientists are confident that orange maize would be especially effective in increasing body stores of vitamin A in populations suffering from vitamin A deficiency. Unlike the form of vitamin A found in supplements and fortified foods, the body regulates conversion of beta-carotene into vitamin A, so that consuming high levels of beta-carotene is not harmful to health.
Major Breakthrough in Breeding for Vitamin A in Maize
At the U.S. Purdue University, West Lafayette/Indiana, researchers have identified a set of genes that can be used to naturally boost the vitamin A content of maize kernels.
Identifying the genes that determine carotenoid levels in maize will help plant breeders develop novel biofortified maize varieties for Africa and the U.S. The dark orange colour of these corn varieties also makes them more culturally acceptable to consumers in African countries, where yellow maize is generally fed only to animals.
According to Torbert Rocheford, professor of agronomy at Purdue University, the researchers used a combination of statistical analysis and prediction models to identify and assess the potential usefulness of genes associated with carotenoid levels in maize. They evaluated data sets from about 200 genetically diverse lines of maize at varying scopes of investigation - from the entire maize genome to stretches of DNA surrounding small sets of genes. They uncovered four genes that had not previously been linked to carotenoid levels in maize kernels.
Their study found that a combination of visually selecting corn with darker orange kernels and using a number of these favourable genes could be an effective way to rapidly convert white and yellow maize varieties to orange maize with higher levels of vitamin A and total carotenoids.
"We now have the genetic information needed to begin developing a major public-private sector collaboration with the goal of providing orange maize with high levels of vitamin A to farmers throughout sub-Saharan Africa," said Rocheford. According to the scientist, the study also showed that using a more targeted approach to predicting the usefulness of a small set of genes was as effective as evaluating the whole maize genome.
Their research - with support from the U.S. National Science Foundation, HarvestPlus and CIMMYT - has yielded varieties of orange maize with markedly higher amounts of vitamin A carotenoids. But further efforts to produce even higher levels will be necessary to offset degradation of nutrients after harvest and reduce the amount of corn African consumers would need to eat to attain enough vitamin A, Rocheford said.
Study on orange maize: Biofortified orange maize is as efficacious as a vitamin A supplement in Zambian children even in the presence of high liver reserves of vitamin A: a community-based, randomized placebo-controlled trial, American Journal of Clinical Nutrition; December 2014 ajcn.087379; First published online October 8, 2014. doi:10.3945/ajcn.114.08737.