European food safety officials issued a warning on Tuesday about potential health problems, including an increased risk of some cancers, linked to long-term use of laxatives such as senna and rhubarb extract.

Laxatives often contain hydroxyanthracenes, a class of substances found in roots, outer leaves, seed and bark of plants such as aloe, rhubarb or senna.

Evidence from animal studies suggests some of these substances can cause cancer of the intestine, the European Food Safety Agency (EFSA) said in a statement.

It said it was not able to set a safe daily intake limit, but repeated its earlier advice against long-term use and consumption at high doses.

In 2013, EFSA found that hydroxyanthracene derivatives in food can improve bowel function, but warned against overuse.