Zakiya Lathan, News Editor, Digital and Audio
Coffee does more than help us feel awake. On National Coffee Day, research into caffeine offers a fascinating glimpse at the chemistry underlying attention — and the everyday ways we alter our own state of consciousness.
For millions of people, changing their state of consciousness is one of the first things they do every morning.
They call it having coffee.
Today, Sept. 29, 2026, is National Coffee Day in the United States and Canada. The National Coffee Association identifies Sept. 29 as the U.S. observance, while the Coffee Association of Canada has likewise recognized the date as National Coffee Day. It is not, however, a worldwide coffee holiday. The International Coffee Organization observes International Coffee Day on Oct. 1, noting that individual countries celebrate national coffee days on different dates.
Coffee’s hold on North American culture is difficult to overstate. According to the National Coffee Association’s September 2026 National Coffee Data Trends report, 66% of American adults drank coffee during the previous day. The nationally representative survey of 1,882 adults was conducted in June.
But behind that familiar morning ritual is an intriguing fact: Coffee changes how we experience being awake.
A 2025 systematic review and meta-analysis published in Psychopharmacology examined 31 randomized, double-blind, placebo-controlled trials involving 1,455 participants. Researchers found that caffeine acutely improved both reaction time and accuracy on tests of attention in healthy, rested adults. Higher doses did not simply produce unlimited improvement; accuracy increased only to a point before declining.
A separate 2025 scientific review found that caffeine may affect alertness, cognition and memory, while noting that coffee also contains polyphenols and numerous other compounds whose neurological effects remain under investigation. The mechanisms behind some of coffee’s effects are still not completely understood.
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That uncertainty matters.
Coffee does not provide evidence for exotic states of consciousness, nor does current research establish that it expands consciousness (despite what this coffee-drinker may believe). What the evidence does demonstrate is something subtler: A common chemical substance can measurably alter attention, fatigue and our subjective sense of alertness.
And there are limits. The U.S. Food and Drug Administration says 400 milligrams of caffeine per day — roughly two to three 12-ounce cups of brewed coffee — is an amount not generally associated with negative effects for most adults, although individual sensitivity varies. Excessive caffeine can contribute to insomnia, anxiety, jitters and other effects.
So on National Coffee Day, that ordinary cup on the desk offers an unusually accessible reminder: Even everyday consciousness is partly chemical — and remarkably easy to nudge.
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