Guarana, an Amazonian seed used for energy and focus, is mainly a caffeine source, not a distinct longevity tool. Its most consistent effect is a small, short-lived gain in reaction speed and alertness after a single serving, plus modest gains in some endurance tasks. Main risks are caffeine's: poorer sleep, restlessness, higher blood pressure, dependence and harm during pregnancy. Caffeine content varies widely between products. No human lifespan studies exist. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Blood pressure (home, seated) | 110–120 / 70–80 mmHg | Caffeine raises it |
| Resting heart rate | 50–70 bpm | Detects stimulant-driven rapid heartbeat |
| Electrocardiogram | Normal heart rhythm; QTc <450 ms (men), <460 ms (women) | Screens for rhythm disorders caffeine can unmask |
| Total sleep time (wearable or diary) | ≥7 hours per night; sleep efficiency ≥85% | Detects caffeine-related sleep loss |
| Fasting glucose | 75–90 mg/dL | Tracks metabolic effects; caffeine can transiently raise glucose |
| HbA1c | <5.4% | Longer-term blood sugar marker |
| LDL cholesterol | <100 mg/dL (many longevity clinicians target <70) | Tracks the observational cholesterol association |
| Ferritin | 50–150 ng/mL | Monitors iron stores given theoretical tannin-iron binding |
Cadence: Blood pressure and heart rate before and one hour after dosing during the first two weeks; sleep data review at 2 weeks and 3 months; blood work every 6–12 months