Efficacy of Yellow Cassava to Improve Vitamin A Status of Kenyan School Children (CASSAVITA)

Efficacy of Yellow Cassava to Improve Vitamin A Status of Mildly Deficient Primary School Children in Kenya: a Randomized Controlled Trial

The overall aim of the project is to provide proof-of-principle that biofortification of cassava with vitamin A is a viable strategy to improve vitamin A status of deficient populations.

Rationale: Vitamin A deficiency is still common in developing countries and has been proven difficult to combat. A promising approach is to replace common crops with varieties that are naturally richer in vitamin A, which is referred to as biofortification. For cassava, yellow β-carotene rich varieties have recently been introduced in Kenya, and these varieties are now ready to be tested for their efficacy to improve vitamin A status in humans. Objective: The primary objective is to measure the effect of daily consumption of provitamin A biofortified cassava (providing 50% of the age-specific RDA) on vitamin A status in children aged 5-13 years with mild to moderate vitamin A deficiency in Kenya. To determine the bioefficacy of provitamin A carotenoids from biofortified cassava relative to that of a daily B-carotene supplement (comparison with positive control group). Secondary objectives are: 1) to measure the effect of the intervention on immune function indicators and morbidity; 2) to determine to what degree the serum retinol response to the intervention depends on serum concentrations of retinol and zinc at baseline; 3) to determine the effect of the intervention on functional indicators such as dark adaptation capacity, gut integrity, hematology indicators and thyroid status; 4) to determine the mediating effect of SNP's in the BCMO1 gene on treatment outcome. Study design & Study population : In this randomized controlled trial, school children aged 5-13 years living in the Kibwezi area, Kenya. Children will be selected from three (or four) primary schools in the area that have been pre-selected based on the prevalence of vitamin A deficiency, location and willingness to participate. Intervention: After screening for eligibility and a 2-week run-in period (n=360) Children will be randomly allocated to three different treatments: 1) 400 g of yellow cassava providing ~50% of the RDA for vitamin A; and a placebo capsule; 2) 400 g of white cassava; and a placebo capsule; 3) 400 g of white cassava and a capsule containing 100 RAE of all-trans β-carotene. Main study parameters/endpoints: The main outcome measure will be differences in serum retinol concentrations between groups. Other outcome measures include other vitamin A status indicators (β-carotene, retinol binding protein, transthyretin), immune function indicators, dark adaptation, iron status indicators, anthropometrics, gut integrity, and thyroid function.

Daily provision of 375 g boiled yellow cassava for 18 weeks, 6 days/week Daily provision of placebo capsule for 18 weeks, 6 days/week

Daily provision of 375 g boiled white cassava for 18 weeks, 6 days/ week Daily provision of placebo capsule for 18 weeks, 6 days/ week

Daily provision of 375 g boiled white cassava for 18 weeks, 6 days/week Daily provision of B-carotene capsule (1400 µg B-carotene)

Comparison of change in serum retinol between yellow cassava group and positive control (B-carotene supplement group)

Inclusion Criteria: Low vitamin A status (retinol binding protein (RBP) at the lowest end of the distribution will be included in the study) Exclusion Criteria: History or signs of infectious or systemic diseases (e.g. tuberculosis, sickle cell anaemia) Anaemia, malaria or acute inflammation at the day of baseline measurements

Talsma EF, Brouwer ID, Verhoef H, Mbera GN, Mwangi AM, Demir AY, Maziya-Dixon B, Boy E, Zimmermann MB, Melse-Boonstra A. Biofortified yellow cassava and vitamin A status of Kenyan children: a randomized controlled trial. Am J Clin Nutr. 2016 Jan;103(1):258-67. doi: 10.3945/ajcn.114.100164. Epub 2015 Dec 16.

Talsma EF, Melse-Boonstra A, de Kok BP, Mbera GN, Mwangi AM, Brouwer ID. Biofortified cassava with pro-vitamin A is sensory and culturally acceptable for consumption by primary school children in Kenya. PLoS One. 2013 Aug 30;8(8):e73433. doi: 10.1371/journal.pone.0073433. eCollection 2013.

Talsma EF, Borgonjen-van den Berg KJ, Melse-Boonstra A, Mayer EV, Verhoef H, Demir AY, Ferguson EL, Kok FJ, Brouwer ID. The potential contribution of yellow cassava to dietary nutrient adequacy of primary-school children in Eastern Kenya; the use of linear programming. Public Health Nutr. 2018 Feb;21(2):365-376. doi: 10.1017/S1368980017002506. Epub 2017 Oct 2.