Scientists say your daily coffee habit may do more than boost your energy. A new study suggests that drinking moderate amounts of caffeinated coffee and tea may reduce the risk of age-related dementia. However, the effects seem to level off after a certain point, and more caffeine isn’t necessarily better for your brain.
A large US study followed 131,821 nurses and health professionals for 43 years, starting when participants were in their early 40s. During the study period, 11,033 participants, or about 8%, developed dementia. Researchers found that people who regularly consumed moderate amounts of caffeinated coffee or tea were less likely to develop this condition.
The effects were greatest for adults under 75 years of age. The group found that consuming about 250mg to 300mg of caffeine per day, equivalent to about 2 to 3 cups of coffee, was associated with a 35% lower risk of dementia. Ingesting higher amounts of caffeine does not provide additional protection.
At the start of the study, women were drinking an average of about four and a half cups of coffee or tea each day, compared to men who were drinking an average of about two and a half cups. Participants who consumed more caffeinated coffee were more likely to be younger, but they also tended to drink more alcohol, smoke more, and eat more calories, all of which are associated with a higher risk of dementia.
Researchers also noticed an unexpected trend regarding decaffeinated coffee. Those who consumed more decaf had faster memory decline. Researchers believe this may be because some people switched to decaf after developing symptoms associated with cognitive decline and dementia, such as sleep problems, high blood pressure, and heart rhythm problems.
Why caffeine helps protect your brain
Scientists say there are several biological explanations for caffeine’s potential effects on the brain. Caffeine blocks adenosine, a chemical that slows down the activity of important brain messengers such as dopamine and acetylcholine. These neurotransmitters naturally become less active with age and diseases such as Alzheimer’s disease, so caffeine may help prevent that decline.
Caffeine may also support brain health by reducing inflammation and helping regulate blood sugar metabolism. Studies have shown that people who regularly drink two or more cups of coffee a day throughout their lives, but do not develop dementia (yet?), have lower levels of amyloid plaques in their brains. These toxic plaques are common in Alzheimer’s patients.
Besides caffeine, coffee and tea contain other compounds that may benefit the brain. Antioxidants and substances that support healthy blood vessels may also play a role in protecting the aging brain.
This study found that one to two cups of tea per day had the strongest protective effect against dementia. The researchers noted that tea consumption in the United States is generally lower than coffee consumption, which may have influenced the results. Although green tea was not studied separately, many previous studies suggest that green tea may also help reduce dementia risk.
Why drinking too much coffee is bad
Researchers say there are several reasons why consuming very high amounts of caffeine may no longer be beneficial. One possibility is that your body processes caffeine differently when you consume more of it. Excess caffeine can disrupt sleep and increase anxiety, both of which can negatively impact brain health.
This idea is consistent with a psychological principle known as the Yerkes-Dotson Law, first proposed in 1908. This law suggests that mental performance only improves with stimulation up to a certain point. When you become overstimulated, such as through stress, anxiety, or too much caffeine, your performance begins to decline.
Although this study focused on medical professionals, the researchers found a similar pattern when they analyzed the results of 38 additional studies. Across these studies, caffeine drinkers had a 6% to 16% lower risk of dementia than non-drinkers, and one to three cups of coffee seemed to have the greatest effect. Tea drinkers also showed promising results, with higher tea intake associated with greater protection.
Moderate caffeine intake may be best
Moderate caffeine intake does not appear to increase 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 coffee to just one cup a day.
Researchers also cautioned that measuring caffeine intake by “cup” is not accurate. The amount of caffeine varies greatly depending on how the coffee is made. Brewed coffee made from whole beans can have significantly different levels of caffeine compared to instant coffee, and the method of preparation can also affect cholesterol levels.
Even relatively small amounts of caffeine can have noticeable effects. Studies have shown that doses as low as 40mg to 60mg may improve mood and alertness in middle-aged adults who typically consume little or no caffeine. The findings suggest that moderation may be key when it comes to coffee and brain health.
