Library.

“Coffee consumption causes miscarriage.”

Coffee has not been established as a cause of miscarriage. Moderate caffeine intake—generally under 200 mg per day—has not been shown to raise miscarriage risk, while some observational studies associate higher intake with greater pregnancy-loss risk. Those studies cannot reliably separate caffeine’s effect from other factors and therefore do not prove causation.

“Scientists at the University of Alaska discovered that drinking three cups of coffee per day allows humans to communicate telepathically with penguins.”

No evidence supports this alleged University of Alaska discovery. Official university sources, PubMed, Nature, Science, and other credible records show no study finding that three cups of coffee enable telepathic communication with penguins. The claim combines ordinary caffeine research with a paranormal assertion that has no accepted scientific basis.

“Coffee consumption stunts human growth (reduces height growth).”

Available evidence does not support the idea that drinking coffee reduces human height growth. Clinical guidance from major pediatric and medical sources treats this as a debunked myth, and studies in adolescents have not shown lower height growth from caffeine intake. Caffeine can still be a problem for children and teens because it can disrupt sleep and cause other health effects, but that is different from stunting height.

“Consuming caffeine via energy drinks is worse for health than consuming an equivalent amount of caffeine via coffee.”

The evidence indicates that energy drinks generally cause more adverse acute cardiovascular effects than the same amount of caffeine from coffee. Randomized trials show larger changes in blood pressure and electrical heart measures after energy drinks, including one direct caffeine-matched coffee comparison. But the claim is broader than the evidence: most studies are short-term, use surrogate markers, and do not prove worse overall or long-term health outcomes in every circumstance.

“Drinking coffee stains teeth yellow.”

Coffee is a well-established cause of extrinsic tooth staining, and the discoloration often appears yellow-brown over time. The evidence from dental studies is strong, but the effect is not uniform or inevitable for every coffee drinker. Staining depends on exposure, enamel condition, and oral hygiene, and some studies use lab conditions that can overstate real-world effects.

“Daily coffee consumption, when the coffee is consumed at least 8 hours before bedtime, is bad for health.”

The evidence does not support the claim. High-quality reviews generally find moderate daily coffee consumption is associated with neutral or favorable health outcomes, not broad harm. The main bedtime-caffeine studies examined 0, 3, and 6 hours before sleep, so they do not establish that coffee consumed at least 8 hours before bed is harmful overall.

“People need to drink extra water to compensate for dehydration caused by drinking coffee.”

The evidence does not support the idea that coffee generally dehydrates people enough to require extra water. In typical amounts, coffee contributes to daily fluid intake and does not cause meaningful net dehydration in most adults. A mild diuretic effect can occur at high caffeine doses, but that does not justify a blanket rule that people must compensate with extra water after drinking coffee.

“Consumption of coffee increases blood pressure.”

Coffee can temporarily raise blood pressure for one to three hours after consumption, particularly in non-habitual drinkers — but the unqualified claim that coffee "increases blood pressure" overstates the evidence. Multiple high-quality meta-analyses, a 2026 Mendelian randomization study, and large-scale population data consistently show that habitual coffee consumption does not produce sustained blood pressure elevation and may even be associated with lower hypertension risk. The claim captures a real but transient effect while omitting the tolerance and long-term context that most readers would need.

“Drinking 3 to 5 cups of coffee per day reduces the risk of cardiovascular disease.”

Large meta-analyses of prospective cohort studies consistently find that drinking 3–5 cups of coffee per day is associated with the lowest observed cardiovascular disease risk — but the claim's causal framing ("reduces the risk") overstates what observational evidence can establish. Residual confounding, variation in cup size and caffeine content, individual genetic differences, and inconsistent findings for specific endpoints like coronary heart disease all represent material omissions. The direction of the evidence is favorable, but the certainty implied by the claim is not warranted.

“Drinking coffee late in the day can disrupt sleep for many people.”

The claim is well-supported by peer-reviewed evidence. A 2023 systematic review found caffeine reduces total sleep time by ~45 minutes, cuts sleep efficiency by 7%, and decreases deep sleep. Multiple clinical and academic sources corroborate these findings. The one dissenting source (NHLBI) is narrowly scoped. The claim's hedged language — "can disrupt" and "many people" — aligns with the evidence, though effects vary by dose, timing, genetics, and tolerance, which the claim doesn't specify.

“Coffee is the most widely consumed psychoactive drug in the world.”

The claim is mostly true but slightly imprecise. Peer-reviewed research consistently identifies caffeine — not coffee specifically — as the world's most widely consumed psychoactive substance. Coffee is caffeine's dominant delivery vehicle (~69% of global intake), but caffeine is also consumed through tea, energy drinks, and soft drinks. In regions like Asia and the UK, tea is the primary caffeine source. No study directly counts unique global coffee drinkers to compare against alcohol (2.4 billion users) or tobacco (1.14 billion). The claim is well-supported in spirit but oversimplifies the picture.

“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.