The juicy tonic combo that could cause ‘serious heart issues’ - potentially ‘deadly’

 By inhibiting the metabolism of enzymes in the body, some fruits may increase the risk of side effects from supplements and drinks.

Grapefruit juice has long been enjoyed for its sensory properties and low-calorie profile. Its popularity, however, was dented after scientists discovered it could have deleterious interactions with an extensive list of drugs. Some studies have suggested the fruit may also interact dangerously with tonic water when consumed by certain people.

The main problem with grapefruit is that it inhibits the enzyme CYP3A4, which metabolises more than 65 percent of all drugs.

“A considerable number of drugs are affected, but the most important causes of concern are probably some of the statins, extensively prescribed as cholesterol reducers,” explains Science Direct.

According to various bodies of research, mixing grapefruit with tonic water containing quinine - a naturally occurring substance - may spur similar effects.

“People who have a heart rhythm disorder should avoid taking grapefruit juice and tonic water together. That combination might worsen some heart conditions,” cautions Medline Plus.

“Also, don’t drink red wine and grapefruit juice together if you take any medications. This combination can make grapefruit juice interact with medications even more.”

Science Direct explains that the tonic and grapefruit combination is dangerous because the juice may inhibit enzymes responsible for the metabolism of quinine.

Thus, the concomitant use of grapefruit juice with quinine may increase concentrations of the nutrient in the blood, and increase the risk of quinine side effects.

In 2003, the American Journal of Medicine highlighted the risk in a report titled "Grapefruit and tonic: a deadly combination in a patient with the long QT syndrome".