Final answer:
Documenting what a stroke patient eats is essential, as it assists in monitoring nutrition, which is vital in post-stroke recovery and prevention of further strokes.
Step-by-step explanation:
The most important instruction by the nurse to the nurse's aide for an older client who has had a stroke would be: "Please document what the client eats in the chart." This is crucial as it helps track the patient's nutrition intake, which is a key component of post-stroke care. Nutrition directly impacts a stroke patient's recovery and helps in preventing another stroke. Additionally, proper documentation ensures that all members of the healthcare team are aware of the patient's nutritional status and can plan care accordingly.
While the other options presented, such as brushing teeth after meals, weighing the client daily, and helping the client choose preferred foods are also important aspects of care, the documentation of food intake takes precedence because it impacts the immediate management of the patient's health needs.