A 4‐Month Intervention with Daily Consumption of Yellow Cassava by Kenyan School Age Children Does Not Affect Thyroid Function Negatively

Abstract

Cassava is a goitrogenous food due to the presence of cyanide, which interacts negatively with thyroid metabolism. Pro‐vitamin A rich yellow cassava has recently been developed as a biofortification strategy to tackle vitamin A deficiency in poor resource areas. We assessed the effect of daily consumption of white or yellow cassava on thyroid function within a randomized controlled trial conducted among Kenyan school children in an area where cassava is not commonly consumed. School children (6‐13 years) were randomized to three treatment groups: 1) White cassava and placebo supplement (n=113); 2) White cassava and β‐carotene supplement (n=113); and 3) Yellow cassava and placebo supplement (n=109). Urinary iodine concentration (UIC) was assessed at baseline; concentrations of thyrotropin (TSH), thyroglobulin (Tg) and free thyroxine (fT4) in serum were assessed before and after the study; and antibodies of thyroid peroxidase (TPO‐Abs) were assessed after the study. At baseline, median UIC was 622 µg/L, 6% of the children had elevated concentrations of TSH (>5.6 mIU/L), 39% had low fT4 concentrations (<10 pmol/L), and 21% had high concentrations of Tg (>40 ng/L). This remained largely unchanged after the study. Serum concentrations of TSH, fT4 and Tg did not differ between groups after intervention. Only one child had raised TPO‐Abs (>9 IU/ml). The children included in the study had excessively high iodine intake and were hypothyroidic at baseline. Thyroid function did not deteriorate further upon cassava intervention.