Downing one-and-a-half large cans of energy drink almost halves blood flow in young adults, a study suggests.
Researchers found the beverages – laden with caffeine and sugar, and popular with children – may lead to vessels contracting.
The narrowing of certain arteries over time can lead to a stroke.
In the small study, 44 non-smoking students in their 20s had blood vessels tested before and 90 minutes after consuming one-and-a-half 500ml cans of energy drink.
At first, vessel dilation was 5.1% in diameter on average. It fell to 2.8% when measured the second time.
Lead researcher Dr John Higgins, of the University of Texas Health Science Centre in Houston in the US, said this suggested “acute impairment in vascular function”.
Makers say the drinks have been confirmed as safe by authorities around the world. In a victory for the Mirror’s Can It! campaign, in June the Government announced proposals to ban the sale of energy drinks to children.
The drinks have previously been linked to health problems associated with the heart. Caffeine can cause blood vessel walls to contract.
The drinks can contain 160mg of caffeine, despite 105mg being the safe daily limit for 11-year-olds.