Ecological variation of intake of cassava food and dietary cyanide load in Nigerian communities.
OBJECTIVE
To study the ecological variation of intake of cassava foods and dietary cyanide load.


METHODS
Ecological study design.


METHODS
Five communities in south-western Nigeria where tropical ataxic neuropathy (TAN) was described as endemic (area A), 11 communities in south-western Nigeria where TAN was described as absent (area B), and five communities in northern Nigeria (area C).


METHODS
Subjects were randomly sampled from selected communities. Intake of cassava foods was estimated from dietary history and dietary cyanide load was estimated from urine thiocyanate concentrations. Residual cyanogens in cassava food samples from the community markets were determined.


RESULTS
In total, 1272 subjects from 21 communities - 238 from area A, 659 from area B and 375 from area C - were selected. Intake of cassava food per person per week was 17 meals in area A, 10 meals in area B, and one meal in area C. Geometrical mean urine thiocyanate concentrations were 73 micromol l(-1), 51 micromol l(-1) and 17 micromol l(-1) in areas A, B and C, respectively. Mean residual cyanogen content in cassava food samples was 16 mg HCN eq kg(-1) (confidence interval (CI) 13-18) in area A, and 13 mg HCN eq kg(-1) in area B (CI 11-14).


CONCLUSIONS
This study shows that the intake of cassava foods and dietary cyanide load is high in several communities in south-western Nigeria, predominantly in communities where TAN has been reported. Dietary cyanide load in these communities appears to be determined by the combination of frequency of intake and cyanogen content of cassava foods. Measures to improve the effectiveness of removal of cyanogen from cassava roots during processing are needed in the affected communities.
Onabolu
A O
AO
International Institute of Tropical Agriculture, c/o LW Lambourn & Co., Croydon, UK. aonabolu@hotmail.com
Oluwole
O S
OS
Bokanga
M
M
Rosling
H
H
D002648:Child; D003430:Cross-Sectional Studies; D003486:Cyanides / Q000008:administration & dosage* / Q000032:analysis; D003906:Developing Countries; D019353:Endemic Diseases; D005260:Female; D005511:Food Handling / Q000379:methods; D006801:Humans; D008297:Male; D002365:Manihot / Q000009:adverse effects / Q000737:chemistry*; D009549:Nigeria / Q000453:epidemiology; D011115:Polyneuropathies / Q000453:epidemiology / Q000209:etiology; D013861:Thiocyanates / Q000652:urine
D003486:Cyanides; D013861:Thiocyanates; C031760:thiocyanate