Pro-vitamin A biofortified cassava improves serum retinol, Hb concentrations in children

Daily intake of β-carotene from biofortified cassava leads to modest improvements in serum retinol and haemoglobin (Hb) concentrations, a study of Nigerian preschool children has shown.

“Consumption of yellow cassava can therefore be considered as an efficacious strategy to improve vitamin A concentration in cassava-consuming populations, and especially so in areas and population groups in which vitamin A sufficiency is even more critical,” the researchers said.

A total of 176 preschool children (aged 3–5 years) were included in this open-label randomized controlled trial conducted in southwestern Nigeria. Participants were randomly assigned to an experimental group (n=88), fed foods prepared from biofortified (yellow) cassava, or a control group (n-88), fed foods prepared from white cassava, twice daily, 6 days a week for 93 days.

Of the children, 159 completed the trial (yellow cassava group: n-80; white cassava group; n=79). Participants consumed 221 and 74 µg/d retinol activity equivalents from intervention foods in the yellow and white cassava groups, respectively. [Am J Clin Nutr 2021;113:221-231]

At the end of the feeding trials, treatment effect of consuming yellow versus white cassava on serum retinol concentrations was 0.06 µmol/L (95 percent confidence interval [CI], 0.004–0.124), after adjustment for baseline retinol concentrations, inflammation, and asymptomatic malaria status.

There were no significant treatment effects found for serum β-carotene (adjusted effect, 3.9 percent, 95 percent CI, –0.6 to 8.6) and gut permeability (adjusted effect, 0.002, 95 percent CI, –0.089 to –0.092). However, there was a significant effect seen for Hb concentrations (adjusted effect, 3.08 g/L, 95 percent CI, 0.38–5.78).

“Much to our surprise, we did find a small but significant treatment effect on the modified primary study outcome: serum retinol concentration,” the researchers said. “This was unexpected because we did not base our sample size on this outcome.”

Moreover, serum retinol concentration was thought to be not responsive to intervention when the vitamin A status of the population is in the sufficient range. Previous studies also failed to show an effect of intervention on this outcome measure, while some did. [Am J Clin Nutr 2014;100:1541-1550; Am J Clin Nutr 2005;81:1080-1087; Am J Clin Nutr 2016;103:258-267; Am J Clin Nutr 1998;68:1058-1067]

“Unexpectedly, we did not find any evidence of iron deficiency in the population even at baseline,” the researchers said. “Possible explanations could be the consumption of foods that are voluntarily fortified or the presence of iron in drinking water, but we currently do not have evidence for either explanation.”

In earlier studies, provision of vitamin A appeared to increase iron indicators and Hb concentrations, which could be explained by the role of vitamin A in stimulating erythropoiesis, thus mobilizing iron to be incorporated into Hb. [Nutrients 2013;6:190-206; Eur J Clin Nutr 2004;58:1223-1230; Am J Clin Nutr 2006;84:580-586]

“However, in a malaria endemic region such as Nigeria, the real effect of such interventions may be masked due to the confounding effect of malaria on serum Hb: Malaria infection initiates haemolysis of both parasitized and nonparasitized red blood cells, which leads to a depletion of Hb concentrations, thus leading to anaemia,” the researchers said. [Trans R Soc Trop Med Hyg 2010;104:175-184]

“In the current study, we found a significant effect of yellow cassava on Hb, but only after adjusting for malaria infection,” they noted.