Dietary Iron Intake and Mental and Behavioral Disorders Due to Use of Tobacco: A Cross-Sectional and Longitudinal Study Based on the UK Biobank

IntroductionOver 1 billion smokers worldwide, one-third of whom have mental and behavioral disorders, exist. However, factors influencing mental and behavioral disorders due to use of tobacco remain unexplored. We aim to investigate the relationship between dietary iron intake and mental and behavioral disorders due to use of tobacco. MethodsUsing large population cohort data from the UK Biobank, we employed logistic and Cox regression to explore the cross-sectional and longitudinal associations between dietary iron intake and mental and behavioral disorders due to use of tobacco. Additionally, we assessed the nonlinear relationship between dietary iron intake and mental and behavioral disorders due to use of tobacco using restricted cubic spline plots. ResultsThe cross-sectional analysis included 50,991 participants. The logistic regression results indicated that dietary iron intake was negatively associated with mental and behavioral disorders due to use of tobacco. A total of 50,921 participants were included in the cohort study. The Cox regression results supported the protective effect of increased dietary iron intake against mental and behavioral disorders due to use of tobacco. The stratified and sensitivity analysis results were consistent with the main results. The restricted cubic spline plots showed a nonlinear relationship between dietary iron intake and mental and behavioral disorders due to use of tobacco. The risk reduction rate initially accelerated and then slowed in the total sample, the two age, and the male groups. In contrast, it declined rapidly at first and then leveled off in the female group. ConclusionThis study found that dietary iron intake has a protective effect against mental and behavioral disorders due to use of tobacco, revealing a nonlinear association between the two. These findings offer valuable insights for the prevention and treatment of mental and behavioral disorders due to use of tobacco in the future. What is already known on this topicExisting research primarily focuses on tobacco as a risk factor for physical diseases. In contrast, the factors influencing mental and behavioral disorders due to use of tobacco have not been adequately explored. Furthermore, findings regarding the relationship between dietary iron intake and mental health in the general population are inconsistent, highlighting the need for this study to clarify the potential association between dietary iron intake and mental and behavioral disorders due to use of tobacco among smokers. What this study addsIn this combined cross-sectional and longitudinal study, we assessed the association between dietary iron intake and mental and behavioral disorders due to use of tobacco using data from UK Biobank. We found that high dietary iron intake was protective against mental and behavioral disorders due to use of tobacco. In the fully adjusted model, the OR (95% CI) and HR (95% CI) for the highest intake group compared to the lowest intake group were 0.41 (0.18 - 0.98) and 0.50 (0.43 - 0.58), respectively. In addition, we found a similar L-shaped nonlinear association between dietary iron intake and mental and behavioral disorders due to use of tobacco utilizing restricted cubic spline plots. How this study might affect research, practice or policyOur study provides evidence of a negative association between dietary iron intake and mental and behavioral disorders due to use of tobacco. For groups that find it difficult to quit smoking, increasing iron intake to an appropriate level may alleviate the discomfort associated with mental and behavioral disorders due to use of tobacco. National mental health is crucial for every country, and this becomes especially important in a modern context where mental stress is increasingly recognized.