Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway

Aakre, Inger; Evensen, Lidunn Tveito; Kjellevold, Marian; Dahl, Lisbeth; Henjum, Sigrun; Alexander, Jan; Madsen, Lise; Markhus, Maria Wik

doi:10.3390/nu12113483

Cited by 34 publications

(26 citation statements)

References 48 publications

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“…While iodine deficiency causes hypothyroidism, iodine excess can cause both hyperthyroidism and hypothyroidism [ 141 ]. Studies in euthyroid humans have observed an increase in TSH levels after seaweed consumption [ 142 , 143 , 144 ] ( Table 1 ). However, Noahsen et al, observed a transient 150% increase in TSH levels in euthyroid individuals after consumption of seaweed (while fT4 levels remained unchanged) that returned to normal within three days [ 145 ].…”

Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelsmentioning

confidence: 99%

“…Although most healthy people tolerate high iodine intake well, in vulnerable individuals, it can lead to the development of hyperthyroidism and even hypothyroidism (reviewed in [ 233 ]). Causes of excess iodine are the consumption of overiodized salt, seaweeds (as already mentioned) [ 141 , 144 , 145 ], consumption of excess iodine through water and milk and taking diary supplements that contain iodine [ 234 ]. Most studies investigating the effect of high iodine intake on TSH and thyroid hormone levels in healthy adults observed an increase in TSH levels and a decrease in the levels of thyroid hormones after excess iodine [ 141 , 144 , 145 , 235 , 236 , 237 , 238 , 239 , 240 , 241 ].…”

Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelsmentioning

confidence: 99%

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Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Leko

Gunjača

Pleić

et al. 2021

IJMS

132

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Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene–environment interactions underlying the pathology of thyroid diseases.

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Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelsmentioning

confidence: 99%

Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelsmentioning

confidence: 99%

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Leko

Gunjača

Pleić

et al. 2021

IJMS

132

View full text Add to dashboard Cite

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“…However, both deficiency and excess iodine can increase the risk of developing thyroid disorders. It is known that excessive iodine intake can result in both hypothyroidism and hyperthyroidism, with or without a goiter [27]. Therefore, it is important to monitor these different types of contaminants in seaweeds and seaweed extracts before consumption or use as ingredients in food, health, and cosmetic products.…”

Section: Introductionmentioning

confidence: 99%

Multi-Step Subcritical Water Extracts of Fucus vesiculosus L. and Codium tomentosum Stackhouse: Composition, Health-Benefits and Safety

et al. 2021

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Mental health and active aging are two of the main concerns in the 21st century. To search for new neuroprotective compounds, extracts of Codium tomentosum Stackhouse and Fucus vesiculosus L. were obtained through multi-step (four step) subcritical water extraction using a temperature gradient. The safety assessment of the extracts was performed by screening pharmaceutical compounds and pesticides by UHPLC-MS/MS, and iodine and arsenic levels by ICP-MS. Although the extracts were free of pharmaceutical compounds and pesticides, the presence of arsenic and high iodine contents were found in the first two extraction steps. Thus, the health-benefits were only evaluated for the fractions obtained in steps 3 and 4 from the extraction process. These fractions were tested against five brain enzymes implicated in Alzheimer’s, Parkinson’s, and major depression etiology as well as against reactive oxygen and nitrogen species, having been observed a strong enzyme inhibition and radical scavenging activities for the step 4 fractions from both seaweed species. Regarding the variation of the chemical composition during the extraction, step 1 fractions were the richest in phenolic compounds. With the increase in temperature, Maillard reaction, caramelization and thermo-oxidation occurred, and the resulting products positively affected the antioxidant capacity and the neuroprotective effects.

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“…This is in accordance with another study, where the estimated iodine content of commercial macroalgae products is estimated to be 6,000 μg/g, and the estimated iodine content per serving was exceeding 10,000 μg for several products ( 6 ). Excessive iodine status was observed in a study of Norwegian macroalgae consumers, where the median UIC was 1,200 μg/L, and the estimated iodine intake from macroalgae was 2,200 μg per day ( 36 ). A long-term excessive iodine intake has been associated with hypothyroidism, goitre, autoimmune thyroid disease and iodine-induced hyperthyroidism in epidemiological studies ( 37 , 38 ).…”

Section: Discussionmentioning

confidence: 99%

Commercially available kelp and seaweed products – valuable iodine source or risk of excess intake?

Aakre

Solli

Markhus

et al. 2021

Food & Nutrition Research

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Background: Seaweeds and kelps, also known as macroalgae, have long been common in the East-Asian diet. During recent years, macroalgae have entered the global food market, and a variety of macroalgae products are now available for consumers. Some macroalgae species are known to be particularly rich in iodine, but little data regarding the iodine content of macroalgae-containing foods exists. Objective: The aim of this research study was to analyse the iodine content in a large variety of commercially available macroalgae-containing foods and supplements and to evaluate whether such products are sources of adequate dietary iodine. Design: Ninety-six different products were collected after surveying the Norwegian market for commercially available macroalgae products, collected from three categories: 1) wholefood macroalgae products (n = 43), 2) macroalgae-containing foods (n = 39), and 3) dietary supplements containing macroalgae (n = 14). All products were analysed for iodine content by inductively coupled plasma-mass spectrometry (ICP-MS). Results: The iodine content in one portion of wholefood macroalgae products ranged from 128 to 62,400 μg. In macroalgae-containing foods, the iodine content ranged from 30 to 25,300 μg per portion, and in supplements it ranged from 5 to 5,600 μg per daily dose. The species with the highest analysed iodine content were oarweed, sugarkelp and kombu, with mean iodine levels of 7,800, 4,469 and 2,276 μg/g, respectively. For 54 products, the intake of one portion or dose would exceed the tolerable upper intake level (UL) for iodine. Discussion and conclusion: The iodine content in the included products was variable and for most products high, exceeding the tolerable upper intake level (UL) if consumed as a serving or portion size. The labelling of macroalgae species included, and declaration of iodine content, were inadequate or inaccurate for several products. As macroalgae-containing products are unreliable iodine sources, inclusion of such products in the diet may pose a risk of consuming excessive amounts of iodine.

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Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway

Cited by 34 publications

References 48 publications

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Multi-Step Subcritical Water Extracts of Fucus vesiculosus L. and Codium tomentosum Stackhouse: Composition, Health-Benefits and Safety

Commercially available kelp and seaweed products – valuable iodine source or risk of excess intake?

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