Caffeinated energy drinks and stimulant supplements showed up disproportionately often in federal reports of serious heart problems — including cardiac arrest and heart attacks — particularly among adults between 18 and 34, according to preliminary research presented at the American Heart Association's Scientific Sessions 2026. The meeting runs Nov. 6–9 in Chicago, and www.heart.org reported the findings on Nov. 2.
The study was led by Sai Samayamanthula, a fourth-year medical student at the University of Virginia School of Medicine in Charlottesville. The work is described as independent and preliminary, and it has not yet been published as a full manuscript in a peer-reviewed journal.
Why it matters
Sales of caffeinated energy drinks have more than doubled in the past decade, topping $20 billion in 2024, according to www.heart.org. These products sit on shelves beside soda and bottled water, and the study's author said that placement shapes how people perceive them.
"These products are marketed as everyday pick-me-ups and sold next to soda and bottled water, so most people assume they carry no real risk," Samayamanthula said, according to www.heart.org.
The research arrives as clinicians increasingly encounter irregular heart rhythms and sudden cardiac death in people who had used these products — many of them young adults with no known heart disease risk factors, www.heart.org reports.
How the study was built
The researchers drew on a government safety database, comparing adverse-reaction reports tied to caffeine- and stimulant-containing products against reports involving other FDA-regulated foods and dietary supplements. The comparison group included soft drinks, meal replacement shakes, protein bars, smoothies and vitamins. The data covered reports from people aged 13 and older filed between 2017 and 2025.
The gap in oversight is central to the picture. Because the FDA treats energy drinks and stimulant supplements as foods or dietary supplements rather than medications, they skip the premarket safety testing that drugs must undergo, according to www.heart.org.
Concentration matters as much as quantity. A 2026 American Heart Association Scientific Statement on caffeine and cardiovascular disease found that up to 400 mg of caffeine a day — roughly five 8-ounce cups of regular black coffee — is generally safe for most adults. But ounce for ounce, some energy drinks carry as much as three times the caffeine of brewed coffee, and certain pre-workout supplements pack more than twelve times as much, www.heart.org reports.
Samayamanthula noted that occasional use likely carries little risk for many healthy people, but regular consumers can blow past the daily caffeine limit quickly. "It's important for people to know that there may be a risk of cardiovascular harm with these products," the author said.
An association, not proof of cause
The researchers do not fully understand why the reports clustered among younger adults. www.heart.org reports several possible explanations: young people may simply consume these products more often; they may use them in risky ways, such as before intense exercise or mixed with alcohol or drugs; or some may carry an undiagnosed heart condition.
Gregory M. Marcus, M.D., M.A.S., FAHA, who chairs the 2026 American Heart Association scientific statement on caffeine and cardiovascular disease and was not involved in the study, cautioned against reading the results as proof of causation.
"This study raises concerns that products with very high amounts of caffeine may be harmful to the cardiovascular system," Marcus said, according to www.heart.org. "Although there are biological reasons why that connection could be possible, the study does not prove that caffeine products cause these events, because other factors may have influenced the results found in this analysis."
Marcus, a professor of medicine at the University of California, San Francisco School of Medicine and associate chief of Cardiology for Research at UCSF Health, added that further research is needed to determine whether the stimulant products are truly responsible for the reported heart events.
The American Heart Association notes that statements and conclusions from studies presented at its scientific meetings belong to the authors and do not necessarily reflect the organization's policy or position. Abstracts presented at the meetings are not peer-reviewed; they are selected by independent review panels and remain preliminary until published in full in a peer-reviewed journal.
What to watch
Samayamanthula said the findings make the case for closer, more systematic safety monitoring of caffeine- and stimulant-containing products. The author also urged clinicians to ask younger patients who report palpitations, chest pain or fainting whether they use these products recently or regularly.
For consumers, the practical takeaway from the research and the association's guidance is arithmetic: check caffeine content per serving and per container, and count it against the 400 mg daily threshold. For regulators and researchers, the open question is whether the pattern in the reports reflects a true biological effect or the circumstances in which these products are used. Watch for the study's full manuscript and peer review, which will determine how much weight the findings carry.
