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Selenium Content of Scottish Soil and Food Products

Institutions
Central Science Laboratory
Start date
2008
End date
2009
Objective
This feasibility study was designed to investigate the link between the underlying geology and the concentrations of selenium both in the overlying soils and in the foods produced on them in order to assist the development of food policy in Scotland.
More information
Research Approach:
A map predicting higher and lower selenium soils in the main agricultural growing areas of Scotland was developed based on geology. Farms growing the foods of interest in areas of predicted higher or lower soil selenium concentrations were identified for sampling. Foods chosen for sampling were commonly consumed foods representative of Scottish agriculture; wheat, broccoli, potatoes, beef and milk. Soil, grass and food products were all sampled according to a strict protocol.

Additional Information:
Key findings:

  • it was generally possible to predict ‘higher’ and ‘lower’ total soil selenium concentrations, based on soil parent material geological information. However, the actual difference in soil selenium concentrations between the two soil types was small (0.48 and 0.37 mg kg-1, average values, respectively).
  • the majority of soil samples (90%) could be classed as selenium deficient , i.e., below the 0.6 mg kg-1 recommended threshold for grazing livestock, irrespective of which predicted soil selenium area they were from.
  • the concentrations of selenium in broccoli, wheat, beef and grass (from the beef farms) were statistically higher in the predicted ‘higher’ selenium regions than in comparable commodities grown in ‘lower’ regions. The concentrations of selenium in milk, grass (from the milk farms) and potatoes showed a similar trend, but were not statistically different.
  • wheat and between-farm potato sample selenium concentrations were significantly correlated with the total soil selenium concentration.
  • selenium concentrations of broccoli, potatoes and milk were comparable to the 2006 Total Diet Study, beef selenium concentrations were marginally lower.
  • the concentrations of selenium in wheat were comparable to data reported previously for Scottish wheat, but were lower than samples from other parts of the UK.
  • broccoli, wheat and potato selenium concentrations were significantly lower (10x, 20x and 5x respectively) than published values for potatoes imported into the UK and published values for broccoli and wheat originating from North America.

    Conclusions:
    The results demonstrated that the concentrations of selenium in the soil were, in general, reflected in the concentrations measured in the resulting plant material.

    Care must be taken however if attempting to estimate how particular plants/animals may respond in a predicted high or low selenium location as the uptake of selenium is affected by many complex environmental and physiological processes.

    Overall, given the limitations of the size of the sample, the data would suggest that consumption of the locally-produced commodities studied here might result in lower dietary selenium intakes compared to consuming similar foods produced in other areas of the UK.

    Given the evidence of a decline in both blood levels of selenium and dietary intake in the UK and the current move to procure locally-produced foods, further investigations to more fully characterise the selenium content of Scottish produce may be warranted if a link between current selenium intakes and health is established. The UK Scientific Advisory Committee on Nutrition (SACN) is in the process of scoping the literature on selenium and health. The Agency is awaiting SACN to complete their work before conclusions on the health consequences of current selenium intakes can be made.

    Results and findings:

  • Higher and lower totals of soil selenium concentrations could usually be predicted from geological data
  • The vast majority of soil samples were low in selenium
  • In general concentrations of selenium in soil were reflected in the food products.

    Find more about this project and other FSA food safety-related projects at the Food Standards Agency Research webpage.

  • Funding Source
    Food Standards Agency
    Project number
    S14042
    Categories
    Legislation and Regulations
    Sanitation and Quality Standards
    Chemical Contaminants
    Food Defense and Integrity
    Commodities
    Produce