WASHINGTON, UNITED STATES: Grapefruit, orange and apple juices can harm the body's ability to absorb certain medications and make the drugs less effective, said a recent study.

The research by Canadian scientists showed that these juices can decrease the effectiveness of certain drugs used to treat heart disease, cancer, organ-transplant rejection and infection, 'potentially wiping out their beneficial effects'.

The study's lead author David Bailey, a professor of clinical pharmacology with the University of Western Ontario, was the first researcher to identify grapefruit juice's potential to increase the absorption of certain drugs two decades ago, possibly turning some doses toxic.

The new findings came as part of his continuing research on the subject, and were presented at the 236th annual meeting of the American Chemical Society in Philadelphia, Pennsylvania, on Tuesday.

'Recently, we discovered that grapefruit and these other fruit juices substantially decrease the oral absorption of certain drugs,' said Prof Bailey.

'The concern is the loss of benefit of medications essential for the treatment of serious medical conditions.'

Volunteers took an antihistamine along with either grapefruit juice, water with naringin (which gives the bitter taste to grapefruit juice), or plain water.

Those who drank the grapefruit juice absorbed only half the amount of the drug, compared to those who drank plain water. Researchers said the water with naringin served to block 'a key drug uptake transporter, called OATP1A2, involved in shuttling drugs from the small intestine to the bloodstream'.

Prof Bailey said: 'This is just the tip of the iceberg. I'm sure we'll find more and more drugs that are affected this way.'

AGENCE FRANCE-PRESSE