A new study has found that older women who consume more than about three regular coffee cups-worth of caffeine per day are less likely to be diagnosed with dementia. A similar amount of caffeine can be obtained from roughly five cups of black tea or eight cans of Coke.

The potential benefits of caffeine on brain health have been hinted at by previous studies, which have found that the drug helps protect mice from developing Alzheimer’s disease and other forms of cognitive impairment. However, very little research has been conducted into its neuroprotective effects in humans.

Reporting their work in the Journals of Gerontology Series A, the study authors explain how they recruited just under 6,500 postmenopausal women aged 65 and older to complete a questionnaire regarding the amount of caffeine-containing drinks – such as coffee, tea, and cola – they consume each day.

Based on the answers given by these women, the researchers were able to split them into two groups: those who consumed more than the median daily intake of caffeine – who, between them, had an average intake of 261 milligrams – and those who drank less than the median amount, with an average of 64 milligrams per day.

Over the following decade, 388 of these women were diagnosed with probable dementia. Interestingly, however, the majority of those diagnosed were from the group that consumed less caffeine, with those who ingested more than the average daily amount being 36 percent less likely to suffer from the condition.

Although the researchers can’t be sure why this is the case, they suggest that the explanation may reside in the way that caffeine blocks adenosine receptors. Since adenosine is involved in regulating a number of neurological processes, such as sleep, anxiety, memory, and cognitive performance, the study authors claim that future research should probably focus on the relationship between caffeine, adenosine, and dementia.