Selenium in rice (Oryza sativa) from different geographic and climatic regions of Sri Lanka
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Date
2015-11-06
Authors
Diyabalanage, S.
Navarathna, T.
Chandrajith, R.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya, Sri Lanka
Abstract
Rice is the main staple food in Sri Lanka as in many other Asian countries. It has been identified that people who consume rice as a staple food are inevitably exposed to significant amounts of different trace elements. Among these trace elements, selenium (Se) is one of the least known, but essential element for both humans and animals. Deficiency of Se can increase the susceptibility of the kidney’s to oxidative damage, but Se becomes toxic to humans when the intake exceeds 900 μg/kg per day. Availability of Se and other bio-important trace elements in rice from Wet Zone (WZ), Dry Zone (DZ) and Intermediate Zone (IZ) were investigated in this study. Concentrations of 19 trace elements in 200 rice samples, including improved (n=188) and traditional rice varieties (n=12) were measured with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after microwave aided acid digestion. The Se contents in improved rice varieties ranged from 0.03 to 261 μg/kg with mean values of 35.4 μg/kg, 42.8 μg/kg and 22.1 μg/kg for WZ, DZ and IZ, respectively. Comparatively higher Se levels were recorded in white polished rice varieties from the DZ and IZ than brown rice varieties from the same regions. Comparatively higher Se levels were observed in traditional rice varieties that varied from 77.51 to 163.8 μg/kg with the mean of 116.4 μg/kg. Among them, the highest Se content was reported in “Maa Vee”, which is widely recommended for diabetes, tuberculosis, constipation, hemorrhoids and cardiovascular diseases in traditional medicine. Based on the average daily consumption of rice by a person, the total daily intake (TDI) of Se was calculated. The TDI are 10.04 μg, 12.14 μg and 6.26 μg from rice of WZ, DZ and IZ, respectively. Results of the study also demonstrate that the Se concentration does not vary significantly among climatic zones. Though Se is available in other foods such as garlic and other vegetables, the recorded values for Se in rice are far below the recommended daily Se intake. Although some early studies indicated higher arsenic (As) contents in Sri Lankan rice, this study reveals that it is well below the Codex Alimentarius recommended maximum allowable limit.
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Keywords
Selenium , Rice , Trace Elements , Traditional rice varieties
Citation
Proceedings of the Peradeniya University International Research Sessions, 5th & 6th November 2015, Vol.19, University of Peradeniya