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

ObjectiveDietary fiber and physical activity are independent determinants of blood pressure. However, their interaction regarding hypertension remains poorly understood. This study examined the association between dietary fiber intake and hypertension. It also aimed to determine if this relationship is modified by physical activity in a representative sample of U.S. adults.MethodsThis cross-sectional study used data from 26,556 U.S. adults (National Health and Nutrition Examination Survey 2007-2018). Dietary fiber intake was assessed via two 24-h recalls and categorized into quartiles. Hypertension was defined by measured blood pressure, self-reported diagnosis, or antihypertensive medication use. Physical activity was quantified and divided into three levels. Missing covariate data were addressed using multiple imputations. Survey-weighted multivariable logistic regression was used to examine the association. A multiplicative interaction term was introduced to assess effect modification by physical activity. An XGBoost was also developed and interpreted using SHapley Additive exPlanation to explore nonlinear associations.ResultsIn the fully adjusted model, lower dietary fiber intake was associated with increased odds of hypertension (OR for Q3 vs. Q4: 1.25; 95% CI [1.08, 1.44]). This relationship showed a potential interaction with physical activity (<i>p</i> for interaction = .067). Stratified analysis showed no association in the low or moderate physical activity groups. 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]). The machine learning model confirmed that higher fiber intake was protectively associated with hypertension, an effect most prominent in physically active individuals.ConclusionThe protective association of dietary fiber with hypertension was observed primarily in highly active adults, but not in less active individuals. These findings highlight the importance of the diet-activity interplay for hypertension prevention.