Scientists say your daily coffee habit may do more than give you an energy boost. New research suggests that drinking a moderate amount of caffeinated coffee or tea could help lower the risk of dementia as people age. However, the benefits appear to level off after a certain point, meaning more caffeine is not necessarily better for the brain.
A large US study followed 131,821 nurses and healthcare professionals for as long as 43 years, beginning when participants were in their early 40s. Over the course of the study, 11,033 participants, about 8%, developed dementia. Researchers found that people who regularly consumed moderate amounts of caffeinated coffee or tea were less likely to develop the condition.
The strongest benefit appeared in adults age 75 and younger. In that group, consuming about 250mg-300mg of caffeine per day, equal to roughly two to three cups of coffee, was linked to a 35% lower dementia risk. Drinking more caffeine than that did not provide additional protection.
At the start of the study, women reported drinking an average of about four and a half cups of coffee or tea daily, while men averaged roughly two and a half cups. Participants who consumed more caffeinated coffee were often younger, but they also tended to drink more alcohol, smoke more, and consume more calories, all of which are associated with a higher risk of dementia.
Researchers also noticed an unexpected trend involving decaffeinated coffee. People who drank more decaf experienced faster memory decline. The researchers believe this may be because some people switched to decaf after developing sleep issues, high blood pressure, or heart rhythm problems, conditions that are themselves tied to cognitive decline and dementia.
Why Caffeine May Help Protect the Brain
Scientists say there are several biological explanations for caffeine’s potential brain benefits. Caffeine blocks adenosine, a chemical that slows the activity of important brain messengers such as dopamine and acetylcholine. These neurotransmitters naturally become less active with age and in diseases like Alzheimer’s, so caffeine may help counteract that decline.
Caffeine may also support brain health by reducing inflammation and helping regulate blood sugar metabolism. Studies have shown that people who regularly drank more than two cups of coffee daily throughout their lives, but did not have dementia (yet?), had lower levels of amyloid plaques in the brain. These toxic plaques are commonly found in people with Alzheimer’s disease.
Coffee and tea contain other compounds beyond caffeine that may benefit the brain as well. Antioxidants and substances that support healthy blood vessels could also play a role in protecting the aging brain.
The study found that one to two cups of tea per day offered the strongest protection against dementia. Researchers noted that tea consumption in the US is generally lower than coffee consumption, which may influence the results. Green tea was not examined separately, although many previous studies have suggested it may also help reduce dementia risk.
Why More Coffee Is Not Better
Researchers say there are several reasons why very high caffeine intake may stop being beneficial. One possibility is that the body processes caffeine differently at higher doses. Excessive caffeine can also interfere with sleep and increase anxiety, both of which may negatively affect brain health.
This idea fits with a psychological principle known as the Yerkes-Dodson law, first proposed in 1908. The law suggests that mental performance improves with stimulation only up to a point. Once stimulation becomes too high, whether from stress, anxiety, or too much caffeine, performance begins to decline.
Although the study focused on healthcare professionals, researchers found similar patterns when they analyzed results from 38 additional studies. Across those studies, caffeine drinkers had a 6%-16% lower dementia risk compared to non-drinkers, with one to three cups of coffee appearing to provide the greatest benefit. Tea drinkers also showed promising results, with higher tea intake linked to greater protection.
Moderate Caffeine Intake May Be Best
Moderate caffeine consumption does not appear to raise long-term blood pressure risk and may even lower the risk of cardiovascular disease, which shares many risk factors with dementia. Still, experts advise people with very high blood pressure to limit themselves to around one cup of coffee per day.
Researchers also caution that measuring caffeine intake by “cups” is not exact. The amount of caffeine can vary widely depending on how coffee is prepared. Freshly brewed coffee made from whole beans may contain very different caffeine levels compared to instant coffee, and preparation methods can also affect cholesterol levels.
Even relatively small amounts of caffeine can have noticeable effects. Studies show that doses as low as 40mg-60mg may improve mood and alertness in middle-aged adults who normally consume little or no caffeine. The findings suggest that when it comes to coffee and brain health, moderation may be the key.