Selenium and iodine in soil, rice and drinking water in relation to endemic goitre in Sri Lanka

Endemic goitre has been reported in the climatic wet zone of south-west Sri Lanka for the past 50 years, but rarely occurs in the northern dry zone. D espite government-sponsored iodised Salt programmes, endemic goitre is stil l prevalent. In recent years, it has been suggested that Se deficiency may be an important factor in the onset of goitre and other iodine deficiency d isorders (IDD). Prior to the present study, environmental concentrations of Se in Sri Lanka and the possible relationships between Se deficiency and e ndemic goitre had not been investigated. During the present study, chemical differences in the environment (measured in soil, rice and drinking water) and the Se-status of the human population (demonstrated by hair samples fr om women) were determined for 15 villages. The villages were characterised by low (< 10%), moderate (10-25%) and high (> 25%) goitre incidence (NIDD, MIDD and HIDD, respectively). Results show that concentrations of soil tota l Se and iodine are highest in the HIDD villages, however, the soil clay an d organic matter content appear to inhibit the bioavailability of these ele ments. Concentrations of iodine in rice are low (less than or equal to 58 n g/g) and rice does not provide a significant source of iodine in the Sri La nkan diet. High concentrations of iodine (up to 84 yg/l) in drinking water in the dry zone may, in part, explain why goitre is uncommon in this area. This study has shown for the first time that significant proportions of the Sri Lankan female population may be Se deficient (24, 24 and 40% in the NI DD, MIDD and HIDD villages, respectively). Although Se deficiency is not re stricted to areas where goitre is prevalent, a combination of iodine and Se deficiency could be involved in the pathogenesis of goitre in Sri Lanka. T he distribution of red rice cultivation in Sri Lanka is coincident with the HIDD villages. Varieties of red rice grown in other countries contain anth ocyanins and procyanidins, compounds which in other foodstuffs are known go itrogens. The potential goitrogenic properties of red rice in Sri Lanka are presently unknown and require further investigation. It is likely that the incidence of goitre in Sri Lanka is multi-factorial, involving trace eleme nt deficiencies and other factors such as poor nutrition and goitrogens in foodstuffs. (C) 2000 Elsevier Science B.V. All rights reserved.