Grapefruit – healthy refreshment and the possible cause of deadly interactions

Citrus paradisi, a beautiful looking fruit with a bitter taste and an undisputable beautiful appearance. This of course is not everything that the grapefruit has to offer. Ample health benefits, which are derived from its low glycemic index, high vitamin and antioxidant content.

This citrus fruit is very present in pop health, most prominently with the citrus diet, popularized due to its low glycemic index and seeming ability to encourage weight loss. These claims aren’t just hot air, and overblown claims. In one study[1], 91 obese patients were given various combinations of grapefruit (juiced, capsuled, fresh) and placebo. During 12 weeks, without other change to their diet the patients suffering from metabolic syndrome consuming fresh grapefruit lost 1.6kg the grapefruit capsule group lost 1.1kg while the grapefruit juice group lost 1.5kg while the placebo group lost only 0.3kg. These changes in weight are statistically significant leading to a conclusion that grapefruit would be a reasonable addition to weight loss. Some interesting facts to note are that 2 hour post-glucose insulin levels were significantly reduced in the patients consuming grapefruit compared to placebo.
However, there is another, darker side to this fruit as well. Many drugs such as calcium channel blockers, immunosuppressants, antihistamines and opiates cause detectable and possibly very damaging variations in drug concentrations caused by augmentation of enzyme activity. One of the most notable interactions is with the popular class of drugs known as benzodiazepines (sedatives, hypnotics), which are used in prevalent conditions such as generalized anxiety disorder. Interactions are most prevalent with midazolam and triazolam (possible 1.3 fold increase of peak concentration; CYP3A4 inhibition; P450 inhibition) [4]. Overdose with these drugs can cause sedation, memory loss, dizziness and if mixed with other depressants (alcohol) can trigger life threatening conditions (extreme CNS depression).

Other important interactions are found with cyclosporine [2], an immunosuppressant drug used in rheumatoid arthritis, psoriasis Chron’s among other diseases. Due to tight therapeutic index of this drug the side effects experienced due to concomitant use with grape fruit can lead to kidney problems, liver problems (already present potentiated side effects of the drug). Other possible interactions are found with antidepressants, decreasing plasma levels and possibly derailing the desired effect of the therapy.
Just some things to consider before enjoying your next grapefruit, a much needed refreshment during the summer.

[1] http://online.liebertpub.com/doi/abs/10.1089/jmf.2006.9.49
[2] http://onlinelibrary.wiley.com/doi/10.1016/0009-9236(95)90032-2/full
[3] http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2710.1999.00247.x/full
[4] http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2710.1999.00247.x/full
[4] http://europepmc.org/abstract/med/10205736