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. 2020 Jan 1;12(1):121.
doi: 10.3390/nu12010121.

Dietary Relationship with 24 h Urinary Iodine Concentrations of Young Adults in the Mountain West Region of the United States

Demetre E Gostas  1 , D Enette Larson-Meyer  1 , Hillary A Yoder  2 , Ainsley E Huffman  3 , Evan C Johnson  4
Affiliations

Dietary Relationship with 24 h Urinary Iodine Concentrations of Young Adults in the Mountain West Region of the United States

Demetre E Gostas et al. Nutrients. .

Abstract

Background: Iodine deficiency is not seen as a public health concern in the US. However certain subpopulations may be vulnerable due to inadequate dietary sources. The purpose of the present study was to determine the dietary habits that influence iodine status in young adult men and women, and to evaluate the relationship between iodine status and thyroid function.

Methods: 111 participants (31.6 ± 0.8 years, 173.2 ± 1.0 cm, 74.9 ± 1.7 kg) provided 24 h urine samples and completed an iodine-specific Food Frequency Questionnaire (FFQ) for assessment of urinary iodine content (UIC) as a marker of iodine status and habitual iodine intake, respectively. Serum Thyroid Stimulating Hormone (TSH) concentration was evaluated as a marker of thyroid function. Spearman correlational and regression analysis were performed to analyze the associations between iodine intake and iodine status, and iodine status and thyroid function.

Results: 50.4% of participants had a 24 h UIC < 100 µg/L). Dairy (r = 0.391, p < 0.000) and egg intake (r = 0.192, p = 0.044) were the best predictors of UIC, accounting for 19.7% of the variance (p ≤ 0.0001). There was a significant correlation between UIC and serum TSH (r = 0.194, p < 0.05) but TSH did not vary by iodine status category (F = 1.087, p = 0.372).

Discussion: Total dairy and egg intake were the primary predictors of estimated iodine intake, as well as UIC. Iodized salt use was not a significant predictor, raising questions about the reliability of iodized salt recall. These data will be useful in directing public health and clinical assessment efforts in the US and other countries.

Keywords: Food Frequency Questionnaire; Iodine Status; adults; dairy intake; iodine intake; iodized salt.

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Conflict of interest statement

The authors declare no conflict of interest. Data collection, analyses, interpretation of results and the writing of the manuscript occurred independently.

Figures

Figure 1
Figure 1
Iodine status based on the World Health Organization (WHO) criteria for urinary iodine concentration (UIC) [15]: <20 µg/L (Severe Deficiency); 20–49 µg/L (Moderate Deficiency); 50–99 µg/L (Mild Deficiency); 100–199 µg/L (Adequate); 200–299 µg/L (More than Adequate); ≥300 µg/L (Excessive).
Figure 2
Figure 2
Estimated iodine intake by Food Frequency Questionnaire versus Urinary Iodine Concentration (a) and Iodine Intake Prediction (using the equation of Zimmerman) [26,27] where Daily Iodine Intake = Urinary iodine (µg/L) × 0.0235 × body weight (kg) (b).
See this image and copyright information in PMC

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