Objectives To investigate the association between adherence to the dietary approach to stop hypertension (DASH) diet and risk of heart failure in a Swedish population. We will use a standard statistical analysis approach (Cox models, etc.) followed by advanced statistical methods (causal inference models). Methods We will use data from the Cohort of Swedish Men (COSM) and the Swedish Mammography Cohort (SMC). We will use data from the 1997 and 2008-2009 assessment of diet and lifestyle. Our exposure will be adherence to the DASH diet and the outcome is heart failure. Heart failure will be ascertained using the Swedish Patient Register. The standard analysis include multivariable Cox proportional hazards regression of the association between adherence to the DASH diet and risk of heart failure. The advanced statistical analysis include the use of the g-formula to take time-varying treatment, confounding and censoring into account. We will use this approach to simulate a hypothetical intervention of the entire cohort adhering to the DASH diet compared with no change on risk of heart failure.