If tasked to design a randomized controlled trial to test whether a high-phytochemical diet reduces systemic inflammation, which feature is most essential to strengthen causal inference?

Random assignment of participants to a well-defined whole-food dietary pattern high in diverse phytochemical-rich foods versus a control diet matched for macronutrients and energy, with objective inflammatory biomarkers measured longitudinally and adherence monitored by biomarkers.

Using a single phytochemical supplement given at very high doses without matching macronutrient content, because isolating one compound is always superior to testing whole-diet patterns for making dietary recommendations.

Recruiting participants and asking them to self-report their diet once at the end of the trial while using subjective wellness surveys as the only outcome measure to capture the broadest range of effects.

Selection of only participants who already have the lowest baseline inflammation and allowing them to choose whether to eat phytochemical-rich foods so that uptake is voluntary and more naturalistic.