Adult Dietary Patterns and Their Association With Iodine Nutrition Levels and Thyroid Function: A Cross-Sectional Study.

Objective: To understand the dietary patterns of adults and explore their association with iodine nutritional levels and thyroid function in adults.

Design: We randomly collected 5 ml of adult urine samples and measured urinary iodine concentration by cerium arsenate-catalyzed spectrophotometry. A serum sample of 5 ml was collected for the determination of free triiodothyronine (FT3), free thyroxine (FT4) and thyrotropin (TSH), and diet-related information was collected through a food frequency questionnaire. Dietary patterns were extracted by principal component analysis and the relationship between dietary patterns and iodine nutrition levels and thyroid function was explored.

Settings: A cross-sectional study involving adults in Xinjiang, China was conducted.

Participants: A total of 435 adults were enrolled in the study.

Results: The overall median urinary iodine of the 435 respondents was 219.73 μg/L.The dietary patterns were PCA1 (staple food pattern), PCA2 (fruit, vegetable, and meat pattern), PCA3 (fish, shrimp, and legume pattern), and PCA4 (Dairy-based protein pattern). The correlation analyses showed that PCA1 and PCA3 were positively correlated with the urinary iodine concentration (UIC). The results of the multivariable analysis showed that PCA1, Q1, Q2, and Q3 were associated with an increased risk of iodine deficiency compared with Q4 [ (OR): 260.41 (95%CI: 20.16, 663.70)], 59.89 (5.64, 335.81), and 2.01 (0.15, 26.16), respectively]. In PCA2, Q3 was associated with an increased risk of iodine deficiency compared with Q4 [OR: 0.16 (0.05, 0.53)]. In PCA3, Q3 was associated with an increased risk of iodine deficiency compared with Q4 [OR: 0.23 (0.06, 0.90)]. In PCA4, Q1 was associated with an increased risk of iodine deficiency compared with Q4 [OR: 31.30 (4.88, 200.64)].

Conclusion: This study demonstrated that of the four dietary patterns, the least dependent staple food pattern (Q1) had a higher risk of iodine deficiency compared to the most dependent staple food pattern (Q4). However, the current evidence on the effect of dietary patterns on thyroid function needs to be validated by further longitudinal studies that include long-term follow-up, larger sample sizes, and repeated measures.