World Food Day
Easing the burden of vitamin A deficiency
developing countries offers more than just a glimmer of hope in
finding a solution to vitamin A deficiency, but funding must
continue to come from the developed world to help with the science.
According to the FAO, foreign aid for agriculture and rural development has continued to decline since the early 1980s, falling from an annual US$9bn to less than US$5bn by the late 1990s. Meanwhile, 854 million people are estimated to be undernourished worldwide.
One of the most serious of these deficiencies is vitamin A deficiency (VAD), a public health problem in more than 50 per cent of all countries, especially in Africa and South-East Asia, according to the World Health Organisation, and causes blindness in up to 500,000 children each year. The human body converts beta-carotene in the diet into vitamin A.
Programs to deliver supplements and fortified foods to those at risk have achieved much but such programs are not sustainable and dependent on continued corporate generosity. But weak market and functional health infrastructures in many developing countries have diminished the impacts of such initiatives.
This has led to more and more research into the biofortication of plants to explore ways of increasing the vitamin A status. Several humanitarian agencies like Harvest Plus, a global alliance of research institutions and implementing agencies, are actively funding biofortified crop breeding in developing countries.
According the HarvestPlus, "Biofortified varieties have the potential to provide ongoing benefits year after year throughout the developing world at a lower recurring cost than either supplementation or postproduction fortification."
This has seen interest in crops such as maize, cassava and rice, staples of many diets, being identified as potential and important targets for biofortification, either by conventional cross-breeding techniques or genetic modification.
Biofortification of such crops have focussed on breeding crops to contain high concentrations of the pro-vitamin A carotenoid, beta-carotene, which is subsequently converted to vitamin A (retinol) in the human body.
In crops such as sweet potato, cassava and maize, beta-carotene is not involved in any photosynthetic processes and is found bound to proteins or in lipid droplets and is release during cooking.
Maize is the preferred staple food of more than a billion people ranging from Latin America to Sub-Saharan Africa, and with an estimated 50 million people in these regions being vitamin A deficient biofortification of this crop could have profound effects.
Using traditional cross-breeding techniques, scientists working with HarvestPlus have reported strains with between 5.0 and 8.6 micrograms of beta-carotene per gram of maize, and some lines have reported to have beta-carotene levels of about 15 micrograms per gram.
These enhanced beta-carotene-containing crops do indeed have an impact on vitamin A status after consumption. A study, published in the October issue of the Journal of Nutrition (Vol. 136, pp. 2562-2567), reported that concentrations of vitamin A in the liver of gerbils eating the high-beta-carotene maize group was 150 per cent that of the control group (0.25 versus 0.10 micromoles/gram, respectively), and equalled that of the group receiving the beta-carotene supplements.
Similar studies are needed to test if such bioavailability is repeated in humans, said the University of Wisconsin (UoW) researchers, who were funded by HarvestPlus.
Rice, a food that provides up to 80 per cent of energy intake in some Asian countries is the obvious vehicle for biofortification in these areas.
However, numerous studies have concluded that polished rice contains practically no pro-vitamin A carotenoids, making traditional cross-breeding techniques redundant. The work in this area, most notably by Syngenta has been in producing transgenic beta-carotene-rich rice.
The company announced in 2005 that a new GM rice, called Syngenta Golden Rice II, produces up to 23-times more provitamin A nutrients than the original beta-carotene-rich Golden Rice This gives the rice a maximum carotenoid level of 37 micrograms per gram of rice and a preferential accumulation of beta-carotene.
Many challenges remain in this area, most notably, said HarvestPlus, "convincing the undernourished to consume biofortified staples."
"Improved mineral content, which generally does not alter appearance, taste, texture or cooking quality, is far less complicated than improving pro-vitamin A content that may alter the colour of the food," said the organisation.
Adding a "transgenic" or "GM" tag to rice also poses challenges to acceptance, as well as attracting attention from anti-GM campaigners in the developed world.
Indeed, Greenpeace have been very vocal in criticising the lack of information given on the bioavailability of beta-carotene from the rice in the body, noting that the original variety was also designed to increase intake of this nutrient but children could not get their daily requirement from eating normal quantities of rice.
The promising results from these programs is an important step in alleviating the burden of vitamin and mineral deficiencies worldwide, and offers a valuable contribution to existing nutrition interventions.
"It is an essential first step in enabling rural households to improve family nutrition and health in a sustainable way," says HarvestPlus.
