Yellow cassava's vitamin A trial

Eating yellow cassava bred to be richer in beta-carotene
increased the level of vitamin A in children's blood by only a
small amount, according to new results.
But some experts, including the scientist leading the trial,
say there is potential for growing yellow cassava in Africa
and parts of Asia to correct vitamin A deficiency - which
leads to blindness and death in many thousands of
children.
Elise Talsma conducted the randomised trial involving 342
children in rural Kenya as part of her PhD at Wageningen
University, the Netherlands, and plans to submit the results
to a peer-reviewed journal.
She measured both beta-carotene, a molecule that the body
can turn into vitamin A, and vitamin A itself in blood
samples of children who consumed 350 grams of cooked
yellow cassava a day for four months, in 2012. Nearly a
quarter (24 per cent) of the children had vitamin A
deficiency, which is defined as having a vitamin A blood
level lower than 0.7 micromoles per litre.
Yellow cassava increased beta-carotene concentration in
children's blood by five times compared with a control
group who ate traditional white cassava.
But the vitamin A concentrations improved on average only
by 0.04 micromoles per litre - not enough to significantly
reduce the number of children with vitamin A deficiency.
Despite the limited result, Talsma believes the effect is
likely to increase when larger volumes are consumed for a
longer period, and with better varieties that are currently
being bred to double the current concentration of beta-
carotene.
She says biofortification is needed to complement other
approaches such as supplementation and fortification of
food, which are not reaching enough people. In the district
she worked in, existing supplementation reached only 31
per cent of children, according to a paper published this
year in the Journal of Epidemiology and Global Health.
And Talsma found through laboratory tests that seven out
of eight bottles of different brands of cooking oil bought in
Kenya that claimed to be fortified with vitamin A did not
contain any more vitamin A than conventional cooking oil.
Talsma previously reported that the majority of children and
their caretakers in her survey in three Kenyan primary
schools prefer the sweeter yellow cassava to white
cassava, in a study she led that was published in PLOS
One.
'Major step' for proof of concept
Erick Boy, nutrition manager at the HarvestPlus programme,
a joint venture between the International Center for Tropical
Agriculture (CIAT) and the International Food Policy
Research Institute (IFPRI), welcomes the results.
"The efficacy of biofortified cassava has been proved for the
first time," he says. "Demonstrating a biologically important
effect under strictly controlled conditions, as in this trial, is
a major step towards proof of concept for biofortification of
cassava with beta-carotene as a potential public nutrition
alternative."
Richard Sayre, who leads a group at the New Mexico
Consortium that has researched high beta-carotene
transgenic cassava, says the results are promising and
consistent with previous studies on transgenic cassava.
But Marianne van Dorp, a food and nutrition specialist at
the Wageningen University and Research centre, is more
critical.
"It is good that the real potential of biofortification in terms
of impact on human nutritional situation is assessed," she
says. "This research shows that the effect is modest, and
that other complementary interventions are needed, such as
supplementation, fortification and dietary diversification,
especially if micronutrient deficiencies are deep."