Patients taking beta blockers are advised to avoid which of the following?

Patients taking beta blockers are advised to avoid caffeine due to its potential to counteract the medication's effects. Beta blockers are generally prescribed to manage conditions such as hypertension and heart rhythm disorders by reducing heart rate and the force of heart contractions. Caffeine is a stimulant that can increase heart rate and blood pressure; thus, consuming it may diminish the therapeutic efficacy of beta blockers.

Additionally, caffeine can lead to jitteriness and anxiety, which can be particularly problematic for patients with cardiovascular conditions. By avoiding caffeine, patients can help ensure that beta blockers work more effectively to control their heart rate and blood pressure.

While the other options listed might have varying interactions or effects, they do not present the same direct conflict with the action of beta blockers as caffeine does. For instance, green leafy vegetables and dietary supplements can generally be consumed without much concern, as long as they do not contain stimulatory ingredients or significant amounts of potassium or other electrolytes that could affect heart function, and antacids can be used, although timing of their use relative to medication doses might be advised in some cases.