The current study, by researchers at the University of North Dakota School of Medicine and Health Sciences, has found that caffeine equivalent to just one cup of coffee a day could protect the blood-brain barrier (BBB) from damage that occurred with a high-fat diet. The barrier protects the brain from the blood that flows around the rest of the body. A leak in this barrier occurs in disorders such as Alzheimer's.
In the new study, the researchers gave rabbits three milligrammes of caffeine each day, the equivalent of a cup of coffee for an average person. The animals were also fed a cholesterol-enriched diet.
The scientists also studied a group of rabbits that were not given any caffeine.
Tests after 12 weeks showed that the blood-brain barrier was significantly more intact with the animals that had the caffeine.
"Caffeine appears to block several of the disruptive effects of cholesterol that make the blood-brain barrier leaky," said lead author Jonathan Geiger.
"High levels of cholesterol are a risk factor for Alzheimer's disease, perhaps by compromising the protective nature of the blood-brain barrier. For the first time we have shown that chronic ingestion of caffeine protects the BBB from cholesterol-induced leakage," he added.
Caffeine appears to protect BBB breakdown by maintaining the expression levels of tight junction proteins. These proteins bind the cells of the BBB tightly to each other to stop unwanted molecules crossing into the central nervous system.
The findings confirm and extend results from other studies showing that caffeine intake protects against memory loss in aging and in Alzheimer's disease.
"Caffeine is a safe and readily available drug and its ability to stabilise the blood-brain barrier means it could have an important part to play in therapies against neurological disorders," said Geiger.
The study appears in the open access publication, Journal of Neuroinflammation.