You may have seen a grapefruit interaction warning on a medication you're taking. The reason for that warning is that the liver can be literally overwhelmed metabolizing grapefruit. That's because it metabolizes grapefruit via the P450 pathway—the same metabolic superhighway your body uses to break down and absorb many common drugs.
While we don’t know for sure why our livers make grapefruit metabolism such a high priority, the result is that medications are not absorbed effectively, so they can either be rendered less effective or accumulate. That brings up another problem—that a drug affected by grapefruit interactions can either be poorly absorbed or reach toxic levels.
What's also impotant to know is that the signs of a grapefruit-drug interaction issue can be insidious and subtle. For instance, someone taking an antidepressant may have too much or too little energy, depending on the specific drug and grapefruit interactions. Someone pumping vitamin C levels with grapefruit to fight an infection make take longer to improve despite the antibiotic they are taking—or develop diarrhea.
Grapefruit Interactions in Women
According to a recent British study, postmenopausal women eating half a fresh grapefruit daily were 30 percent more likely to develop breast cancer than those not consuming the fruit. And we know that even HRT can be affected by grapefruit. One speculation is that the grapefruit interactions in the body may directly increase estrogen levels.
Grapefruit Interactions in Men
Men should be aware that grapefruit augments the body’s production of aromatase, an enzyme that converts testosterone to estrogen in men, often causing an undesirable feminizing effect. In fact, I took a dietary history on one of my male patients who complained of erectile dysfunction (ED). When I learned the gentleman ate or drank grapefruit/grapefruit juice every day, I advised him to stop immediately. As a result, the ED resolved in just a few weeks.
So, enjoy grapefruit and grapefruit juice on occasion and check with your doctor or pharmacists for interactions with medications you may be taking.
Now it's your turn: Have you had difficulties with a grapefruit-drug interaction?