Physical activity modifies the association between dietary fiber and hypertension: A cross-sectional study of U.S. adults from NHANES 2007-2018.

Lower dietary fiber intake was associated with increased odds of hypertension in the fully adjusted model.

• Cross-sectional study of 26,556 U.S. adults from NHANES 2007-2018
• Dietary fiber intake was assessed via two 24-h dietary recalls and categorized into quartiles
• OR for Q3 vs. Q4: 1.25; 95% CI [1.08, 1.44] in the fully adjusted model
• Hypertension was defined by measured blood pressure, self-reported diagnosis, or antihypertensive medication use
• Missing covariate data were addressed using multiple imputations

Physical activity showed a potential interaction with the dietary fiber–hypertension relationship.

• A multiplicative interaction term was introduced to assess effect modification by physical activity
• p for interaction = .067
• Physical activity was quantified and divided into three levels: low, moderate, and high
• The interaction did not reach conventional statistical significance (p < .05) but was considered a potential modifier

The association between lower dietary fiber intake and higher odds of hypertension was significant only among individuals with high physical activity.

• Among individuals with high physical activity, lower fiber intake was associated with significantly higher odds of hypertension: OR for Q1 vs. Q4: 1.50; 95% CI [1.10, 2.04]
• Stratified analysis showed no statistically significant association in the low or moderate physical activity groups
• This suggests the protective effect of dietary fiber on hypertension is concentrated in highly active adults

An XGBoost machine learning model with SHAP interpretation confirmed that higher fiber intake was protectively associated with hypertension, most prominently in physically active individuals.

• XGBoost was developed and interpreted using SHapley Additive exPlanation (SHAP) values to explore nonlinear associations
• The machine learning model corroborated findings from the survey-weighted multivariable logistic regression
• The protective effect of higher fiber intake was described as 'most prominent in physically active individuals'
• The machine learning approach was used to capture potential nonlinear relationships between dietary fiber and hypertension

Dietary fiber and physical activity are described as independent determinants of blood pressure whose interaction regarding hypertension has been poorly understood.

• The study was designed to address the gap in understanding the interaction between dietary fiber and physical activity on hypertension
• The sample was drawn from six cycles of NHANES (2007–2018), representing U.S. adults
• Survey-weighted multivariable logistic regression was used to account for the complex survey design of NHANES