Environmental Geochemistry and Health

, Volume 39, Issue 4, pp 835–845 | Cite as

Elemental composition of Malawian rice

  • Edward J. M. Joy
  • E. Louise Ander
  • Martin R. Broadley
  • Scott D. Young
  • Allan D. C. Chilimba
  • Elliott M. Hamilton
  • Michael J. Watts
Original Paper


Widespread potential dietary deficiencies of calcium (Ca), iron (Fe), iodine (I), selenium (Se) and zinc (Zn) have been identified in Malawi. Several deficiencies are likely to be compounded by high phytic acid (PA) consumption. Rice (Oryza sativa) is commonly consumed in some Malawian populations, and its mineral micronutrient content is important for food security. The considerable irrigation requirements and flooded conditions of paddy soils can also introduce or mobilise potentially toxic elements including arsenic (As), cadmium (Cd) and lead (Pb). The aim of this study was to determine the mineral composition of rice sampled from farmers’ fields and markets in Malawi. Rice was sampled from 18 extension planning areas across Malawi with 21 white (i.e. polished) and 33 brown samples collected. Elemental composition was determined by inductively coupled plasma-mass spectrometry (ICP-MS). Arsenic speciation was performed using high-performance liquid chromatography (HPLC)-ICP-MS. Concentration of PA was determined using a PA-total phosphorus assay. Median total concentrations (mg kg−1, dry weight) of elements important for human nutrition in brown and white rice, respectively, were: Ca = 66.5 and 37.8; Cu = 3.65 and 2.49; Fe = 22.1 and 7.2; I = 0.006 and <0.005; Mg = 1130 and 265; Mn = 18.2 and 9.6; Se = 0.025 and 0.028; and Zn = 17.0 and 14.4. In brown and white rice samples, respectively, median PA concentrations were 5438 and 1906 mg kg−1, and median PA:Zn molar ratios were 29 and 13. Concentrations of potentially toxic elements (mg kg−1, dry weight) in brown and white rice samples, respectively, were: As = 0.030 and 0.006; Cd  ≤ 0.002 and 0.006; Pb = 0.008 and 0.008. Approximately 95 % of As was found to be inorganic As, where this could be quantified. Malawian rice, like the more widely consumed staple grain maize, contains inadequate Ca, I, Se or Zn to meet dietary requirements. Biofortification strategies could significantly increase Se and Zn concentrations and require further investigation. Concentrations of Fe in rice grain varied greatly, and this was likely due to contamination of rice samples with soil. Risk of As, Cd or Pb toxicity due to rice consumption in Malawi appears to be minimal.


Arsenic Micronutrient deficiencies Phytic acid Rice Selenium Zinc 



EJMJ, MRB, ADCC, ELA, SDY and MJW conceived the study; EJMJ and ADCC collected samples; MJW and EMH analysed the samples; EJMJ drafted the text and figures; all authors read, contributed to and approved the final manuscript. EJMJ’s PhD studentship was funded by the University of Nottingham, UK and the British Geological Survey. The authors would like to thank Paul Williams (Queens University Belfast) and Andy Meharg (University of Aberdeen) for providing valuable advice, references and supplementary data during the manuscript drafting.

Supplementary material

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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • Edward J. M. Joy
    • 1
    • 2
    • 3
  • E. Louise Ander
    • 2
  • Martin R. Broadley
    • 3
  • Scott D. Young
    • 3
  • Allan D. C. Chilimba
    • 4
  • Elliott M. Hamilton
    • 2
  • Michael J. Watts
    • 2
  1. 1.Department of Population HealthLondon School of Hygiene & Tropical MedicineLondonUK
  2. 2.Inorganic Geochemistry, Centre for Environmental GeochemistryBritish Geological SurveyKeyworth, NottinghamUK
  3. 3.School of BiosciencesUniversity of Nottingham, Sutton Bonington CampusLoughboroughUK
  4. 4.Department of Agricultural Research ServicesMinistry of Agriculture, Irrigation and Water DevelopmentLilongwe 3Malawi

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