Ultra-processed food consumption and thyroid hormone profiles: a cross-sectional analysis of NHANES 2007-2012

Ultra-processed foods (UPFs) have been increasingly linked to adverse metabolic outcomes. The aim of this study was to assess the association between UPF consumption and thyroid hormone levels in a nationally representative sample of U.S. adults.

A cross-sectional analysis was conducted using data from 5,961 adults aged ≥ 18 years participating in NHANES 2007-2012. Dietary intake was assessed using two 24-hour dietary recall and categorized using the NOVA classification system. UPF intake was expressed as a percentage of total daily energy consumption and divided into tertiles. Serum levels of thyroid-stimulating hormone (TSH), free and total triiodothyronine (FT3, TT3), and thyroxine (FT4, TT4) were measured using standardized immunoassays. Weighted linear regression, adjusting for covariates, was used to evaluate associations.

Participants had a mean age of 46.8 years and 51.9% were men. Higher UPF intake was linked to younger age, lower income, and greater obesity prevalence (P < 0.001). In fully adjusted models, higher UPF intake was associated with small decreases in FT4 and TT4 and small increases in TSH. Each tertile increase in UPF intake was associated with lower FT4 (β = -0.01 ng/dL, 95% CI - 0.015 to - 0.007) and TT4 (β = -0.12 µg/dL, 95% CI - 0.16 to - 0.09), alongside a modest increase in TSH (β = 0.02, P = 0.012). FT3 associations were weaker and less consistent.

Higher UPF consumption was associated with small differences in thyroid hormone levels in this cross-sectional analysis. Given the modest effect sizes and cross-sectional design, these findings should be interpreted cautiously.