Feed-derived iodine overrides environmental contribution to cow milk

McKernan, Claire; Meharg, Caroline; Carey, Manus; Donaldson, E.; Savage, Laurie; Meharg, Andrew A.

doi:10.3168/jds.2019-17446

Cited by 10 publications

(9 citation statements)

References 35 publications

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“…Results from this study report soil selenium concentrations are in uenced by soil characteristics and re ect in the grass selenium concentration. Despite the strong environmental relationship, a disconnect in relation to milk selenium concentration and the agricultural land, similar ndings were reported investigating iodine in agronomic environment (McKernan et al 2020). The variable milk selenium concentrations reported in this study is attributable to inconsistent farm management practices where the fodder provided to herds is variable.…”

Section: Discussionsupporting

confidence: 76%

“…Water samples were not collected and analysed in this study, as reported water selenium concentrations are < 10µg/L, subsequently are unlikely to in uence milk selenium concentrations (WHO, 2011). Further details of the sample collection approach have already been reported in McKernan et al, (2020).…”

Section: Sample Collectionmentioning

confidence: 99%

“…Sample preparation and analysis follows that of McKernan et al (2020) in an associated study on iodine.…”

Section: Sample Analysismentioning

confidence: 99%

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The dynamics of selenium in dairy agroecosystems.

McKernan

Meharg

Carey

et al. 2022

Preprint

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Environmental selenium deficiency and toxicity can result in Keshan disease and selenosis, respectively. Due to dietary preferences, milk is considered a primary source of selenium, where, in controlled environments milk selenium concentration reflects the selenium provided in fodder to lactating cows. However, the movement of selenium through agroecosystems is not well understood, and the aim of this current study was to investigate the variables that me responsible for transfer of selenium from soil to milk. Investigated parameters include spatial variability, soil selenium status, season, herd diet and husbandry of cattle. Farm-based sample collections were carried out, where soil, grass, silage and milk were collected over 48 geographically spaced locations over Northern Ireland during both summer and winter. Selenium concentrations were determined using ICP-MS. Median selenium concentrations for soil (0.46 mg/kg DM), grass (0.06 mg/kg DM) silage (0.03 mg/kg DM) and milk (0.23 mg/kg DM). Results showed that soil selenium concentrations were significantly affected by the pH and organic matter composition of soil. Additionally, a statistically significant relationships between soil and grass selenium concentrations were also found. Despite these strong environmental relationships with grass, these relationships were not reflected in the milk selenium concentrations, indicating a disconnect between the selenium concentration in the agricultural environment and the milk from which it is derived. Selenium was higher in milk in winter months as compared to summer, related to supplemental feed practices over the winter when cows are housed.

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Section: Discussionsupporting

confidence: 76%

Section: Sample Collectionmentioning

confidence: 99%

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The dynamics of selenium in dairy agroecosystems.

McKernan

Meharg

Carey

et al. 2022

Preprint

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“…With no formal iodine food fortification programme in the UK or ROI, good dietary sources are essential to meet requirements. Food content varies with season and soil content with coastal areas having higher levels [ 21 ]. Dietary habits may change during pregnancy, but it is not known how this affects iodine nutrition.…”

Section: Introductionmentioning

confidence: 99%

Thyroglobulin levels among iodine deficient pregnant women living in Northern Ireland

et al. 2022

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Background Iodine deficiency has re-emerged among pregnant cohorts in the UK. Thyroglobulin (Tg) is a protein produced uniquely by the thyroid gland which appears to mount a U-shaped response to extremes of iodine status. Tg has been suggested as an alternative marker for chronic iodine deficiency but the value of Tg in pregnancy has not been fully elucidated. A recent non-European study suggested a median Tg ≤10 µg/L with <3% of values >44 µg/L was indicative of sufficiency in the second trimester of pregnancy. Methods We measured serum Tg levels in each trimester in 241 pregnant women living in Northern Ireland, a population with mild iodine deficiency at all stages of pregnancy as defined by urinary iodine concentration (UIC) and iodine: creatinine ratio (ICR). Women with Tg antibodies (6% in 1st trimester) were excluded. Results The median UIC in this cohort was in the deficient range at 73, 94 and 117 µg/L in sequential trimesters (adequacy ≥ 150 µg/L). Corresponding median Tg levels were 19, 16 and 16 µg/L respectively. Median Tg for all samples was 17 μg/L (IQR 11–31) suggestive of iodine deficiency. Tg was >44 μg/L in 14.3%, 9.4% and 12.4% of women in sequential trimesters respectively. Women with either UIC/ICR below the cut-offs 150 µg/L and 150 µg/g creatinine had higher Tg concentrations in 1st and 2nd trimester (p < 0.01; p < 0.001) but not in 3rd trimester. Conclusion This study adds to the evolving evidence that Tg measurement is of value in reflecting iodine status in pregnancy.

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“…The flow of iodine through agro‐ecosystems including milk, soil, silage, grass and different animal feeds is not well understood 48 . A recent UK report suggested that natural iodine inputs into the environment are dominated by atmospheric deposition, especially sea spray, and so the location of farms relative to the coast and prevailing wind direction is important 49 . The levels of iodine in supplemental feeds were approximately 10‐fold higher than those in forage‐derived feeds and the practice of feed supplementation led to elevated milk iodine 49 …”

Section: Changes In Farming Practicesmentioning

confidence: 99%

Iodine status in UK–An accidental public health triumph gone sour

Woodside

Mullan

2020

Clinical Endocrinology

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The improvement in iodine status among the UK population from the 1930s onwards has been described as an ‘accidental public health triumph’ despite the lack of any iodine fortification program. However, iodine deficiency in the UK has re‐emerged in vulnerable groups and is likely due to a combination of changing farming practices, dietary preferences and public health priorities. The UK is now among only a minority of European countries with no legislative framework for iodine fortification. The experience of folic acid fortification and the 28‐year delay in its implementation lays bare the political difficulties of introducing any fortification program in the UK. If iodine fortification is not an imminent possibility, then it is important to explore other options: how to change farming practice especially on organic farms; encourage dairy intake; protect and expand our public health programs of milk provision for vulnerable groups and embark on education programs for women of childbearing potential and healthcare professionals. This review explores how the UK may have arrived at this juncture and how the iodine status of the nation may be improved at this time of major political and public health upheaval.

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Feed-derived iodine overrides environmental contribution to cow milk

Cited by 10 publications

References 35 publications

The dynamics of selenium in dairy agroecosystems.

The dynamics of selenium in dairy agroecosystems.

Thyroglobulin levels among iodine deficient pregnant women living in Northern Ireland

Iodine status in UK–An accidental public health triumph gone sour

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