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Review
. 2021 Apr;10(2):101-108.
doi: 10.1159/000512971. Epub 2021 Jan 27.

Iodine, Seaweed, and the Thyroid

Peter P A Smyth  1
Affiliations
Review

Iodine, Seaweed, and the Thyroid

Peter P A Smyth. Eur Thyroid J. 2021 Apr.

Abstract

Backgound: Even a minor iodine deficiency can result in adverse thyroidal health consequences while excess iodine intake can also result in thyroid function disorders. One source of iodine is seaweed which as a foodstuff is enjoying an increasing profile in Western countries. Apart from its potential involvement in thyroidal health, gaseous iodine released from seaweeds plays a significant role in influencing coastal climate through cloud formation.

Summary: Sources of dietary iodine, its assessment, recommended dietary intake, and consequences of iodine excess are outlined. The benefits and possible dangers of dietary intake of iodine-rich seaweed are described. Studies linking seaweed intake to breast cancer prevalence are discussed as is the role of gaseous iodine released from seaweeds influencing weather patterns and contributing to iodine intake in coastal populations.

Key messages: Universal salt iodization remains the optimum method of achieving optimum iodine status. Promoting increased dietary iodine intake is recommended in young women, in early pregnancy, and in vegan and vegetarian diets. Even where iodine intake is enhanced, regular assessment of iodine status is necessary. Caution against consumption of brown seaweeds (kelps) is required as even small amounts can have antithyroid actions while product labelling may be insufficient. Gaseous iodine produced from seaweeds can have a significant effect on cloud formation and associated global warming/cooling. Increased overall iodine deposition through rainfall and apparent uptake in populations dwelling in seaweed-rich coastal regions may provide a partial natural remedy to global iodine deficits.

Keywords: Atmospheric iodine; Iodine; Iodine deficiency; Seaweed; Thyroid; Urinary iodine.

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Conflict of interest statement

The author has no conflicts of interest to declare.

Figures

Fig. 1
Fig. 1
Iodide (I−) and iodine (I2) uptake and deposition. I− in seaweed reacts with O3 to produce I2 gas leading to atmospheric aerosol generation resulting in cloud formation which reflects sunlight partially offsetting global warming. Iodinated compound can be deposited in rain, and gaseous I2 can be taken up by respiration.
See this image and copyright information in PMC

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