Which statement about caffeine in nutrition and performance is most accurate?

Which statement about caffeine in nutrition and performance is most accurate?

• A. It has no effect on performance.
• B. Caffeine can improve alertness and performance, but effects vary between individuals.
• C. The safe daily limit is 800 mg for most adults.
• D. Caffeine can improve alertness and performance; typical safe limit is up to 400 mg/day for most adults, with variability by sensitivity.

Answer: (D)