Cases of dementia are set to explode in the coming decades as populations around the world get older. Age is not the only driver of brain decline, however. Research published late last year in the journal Nutritional Neuroscience found a worrying association between coffee intake and a heightened risk of brain decline.

The research makes a strong case for stopping at five or six cups per day – drinking more than that could harm your brain.

Researchers looked at about 400,000 people who regularly drank coffee (either caffeinated or decaffeinated).

Daily intake was divided into several categories, from one to two cups to more than six cups.

Approximately 18,000 people had their brain volume measured with MRI. At the 11-year follow-up, the investigators found that compared with light coffee drinkers (one to two daily cups), heavy coffee drinkers (more than six cups per day) tended to have smaller amounts of total brain volume, especially in the hippocampus, the region responsible for short- and long-term memory.

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Researchers in this study found that drinking tea and coffee was linked to a lower risk of having an ischaemic stroke (caused by a blocked blood vessel) and vascular dementia, rather than a haemorrhagic stroke (caused by a burst blood vessel) or Alzheimer’s disease.

Commenting on the findings at the time, Doctor Rosa Sancho, Head of Research at Alzheimer’s Research UK, said: “For most of us, our risk of dementia depends on the complex interaction of our age, genetics and lifestyle. We know that stroke increases the risk of developing vascular dementia. Understanding which aspects of our lifestyle have the greatest effect on our brain health is key to empowering people to make informed decisions about their lives.

“Studies like this one are not able to pinpoint cause and effect, and while the researchers attempted to control for other factors that could affect a person’s risk of stroke and vascular dementia, no firm conclusions can be made about whether tea or coffee cause this lower risk. Participants only reported tea and coffee consumption at the beginning of the study, and there is no data on long-term habits, so it’s not clear how relevant the findings are to long-term brain health.

“While previous studies have looked at associations between tea and coffee consumption and better brain health, there has been inconsistency in findings. Future research with participants of a range of ages and ethnicities will be needed to fully understand what types of dementia and stroke are associated with tea and coffee drinking. Participants in this study reported themselves to be mainly White British (96 percent), therefore we cannot infer an association that is relevant to everyone in the UK.”