Most people think of caffeine as the pick-me-up in their morning coffee or tea, but new research suggests it could have surprising effects on something much more serious: blood transfusions.
A study from the University of Colorado Anschutz Medical Campus has found that caffeine may reduce the quality of donated blood and make transfusions less effective for patients—especially for those with certain genetic traits.
“Caffeine’s effects on the brain and nervous system are well known, but this is the first time we’ve seen how it can change the biology of red blood cells,” said Angelo D’Alessandro, Ph.D., senior author of the study.
“That morning cup of coffee could actually influence how well donated blood works in patients who need it.”
The study, published in Haematologica, was part of a large project called REDS RBC-Omics, which analyzed samples from more than 13,000 blood donors.
The results showed that higher caffeine levels in donated blood were linked to red blood cells that broke down more easily during storage.
When this blood was later transfused, patients had smaller increases in hemoglobin—the protein that carries oxygen—and showed more evidence of cell damage.
These effects were even more pronounced in people with common variations in the ADORA2B gene, which helps red blood cells function in low-oxygen conditions.
This suggests that both genetics and lifestyle choices may determine how well a blood transfusion works.
The researchers say the findings could change the way blood banks think about donations. In Europe, some countries already advise donors to limit caffeine before giving blood. In the U.S. and elsewhere, however, caffeine is not discouraged.
In fact, it may even be seen as helpful, since caffeine can temporarily raise blood pressure and improve circulation, which can make blood donation easier. But caffeine is also a mild diuretic, meaning it can dehydrate donors and slow blood flow—potentially making collection more difficult.
“Caffeine consumption is one of the most common dietary habits in the world,” D’Alessandro said. “Because its effects are short-lived, simply adjusting intake around the time of donation could reduce its negative impact on blood quality.”
The study also connects transfusion medicine to sports science. Caffeine is known to boost athletic performance, partly by increasing oxidative stress in red blood cells. This stress comes from two actions: blocking the ADORA2B receptor and inhibiting a key enzyme called G6PD. While this stress can damage cells in transfusions, in exercise it may actually help trigger beneficial adaptations.
“These insights show how something as ordinary as caffeine links together blood donation, human genetics, and even sports performance,” said Travis Nemkov, Ph.D., a co-author of the study.
The researchers say more work is needed, but their findings highlight a simple idea with big implications: your morning coffee may affect not just you, but also the patients who depend on donated blood.
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Source: KSR.
