3 published verifications about caffeine caffeine ×
“Consuming caffeine while cortisol levels are elevated reduces the stimulant effect of caffeine compared to when cortisol levels are not elevated.”
The available evidence does not support this claim as stated. Studies show that habitual caffeine use can blunt caffeine's ability to further raise cortisol levels — but this is a different outcome from caffeine's stimulant effect on alertness, which is primarily mediated through adenosine receptor blockade. No source in the evidence pool directly measures whether pre-existing elevated cortisol reduces caffeine's wakefulness or alertness properties. The claim conflates two distinct physiological pathways, creating a materially misleading impression.
“Taking caffeine before a period of sleep deprivation can fully restore social memory function that would otherwise be impaired.”
A 2026 peer-reviewed study did show caffeine reversed social memory deficits in male mice via a specific hippocampal CA2 mechanism. However, the claim's unqualified language — "fully restore social memory function" — overgeneralizes from a single animal model and one narrow social-recognition assay. No human evidence confirms this effect. Broader research shows caffeine often only partially rescues cognition under sleep deprivation and can disrupt recovery sleep. The core finding is real but the claim's framing is misleading.
“Drinking coffee causes dehydration in humans.”
This claim is false. The scientific consensus, supported by peer-reviewed meta-analyses and major health authorities like the NHS, is clear: moderate coffee consumption does not cause dehydration in healthy adults. Coffee's mild diuretic effect is transient and far outweighed by the water content of the beverage itself. The only studies showing negative fluid balance used extreme caffeine doses in caffeine-deprived subjects—conditions irrelevant to normal coffee drinking. Regular consumers develop tolerance to caffeine's diuretic effects.