Korean J Intern Med.  2020 Mar;35(2):392-399. 10.3904/kjim.2017.375.

Association between urinary sodium levels and iodine status in Korea

• Ahn J
• Lee JH
• Lee J
• Baek JY
• Song E
• Oh HS
• Kim M
• Park S
• Jeon MJ
• Kim TY
• Kim WB
• Shong YK
• Kim WG

• KMID: 2502025
• DOI: http://doi.org/10.3904/kjim.2017.375

Abstract

Background/Aims
To evaluate the association between the urinary sodium concentration and iodine status in different age groups in Korea.
Methods
This nationwide, population-based, cross-sectional study used data from the Korean National Health and Nutrition Examination Survey (VI 2-3, 2014 to 2015). We included 3,645 subjects aged 10 to 75 years with normal kidney function and without a history of thyroid disease. Adequate iodine intake was defined as a urinary iodine/creatinine (I/Cr) ratio of 85 to 220 µg/g. The urinary sodium/ creatinine (Na/Cr) ratios were classified as low (< 47 mmol/g), intermediate (47 to 114 mmol/g), or high (> 114 mmol/g).
Results
The median urinary iodine concentration (UIC) was 292 µg/L (interquartile range [IQR], 157 to 672), and the median urinary I/Cr ratio was 195 µg/g (IQR, 104 to 478). Iodine deficiency (< 100 µg/L) and iodine excess (> 300 µg/L) were observed in 11.3% and 49.0% of subjects, respectively. The UIC was significantly associated with the urinary sodium concentration, and the urinary I/Cr ratio was significantly correlated with the urinary Na/Cr ratio (both p < 0.001). The distributions of UIC, urinary I/Cr ratio, and Na/Cr ratio varied among age groups. Low urinary I/Cr and Na/Cr ratios were most common in young adults (age, 19 to 29 years), while high urinary I/Cr and Na/Cr ratios were most common in elderly people (age, 60 to 75 years).
Conclusions
Iodine intake was significantly associated with sodium intake in the Korean population. Our study suggested that an adequately low salt intake might be helpful for preventing iodine excess in Korea.

Keyword

Iodine; Sodium; Diet; Urine; Korea