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Effect of Drinking Grapefruit Juice on the Prohormones

author image Kathryn Gilhuly
Kathryn Gilhuly is a wellness coach based in San Diego. She helps doctors, nurses and other professionals implement lifestyle changes that focus on a healthy diet and exercise. Gilhuly holds a Master of Science in health, nutrition and exercise from North Dakota State University.
Effect of Drinking Grapefruit Juice on the Prohormones
A tall glass of grapefruit juice beside a halved grapefruit. Photo Credit Umberto Leporini/iStock/Getty Images

Prohormones, compounds sometimes taken as dietary supplements, act like steroids in your body, as explained by UK-Muscle. Like steroids, prohormones work to quickly build muscle and strength. Some athletes and bodybuilders take prohormones with grapefruit juice to intensify the effects of hormones. This may work but could prove dangerous. Talk to your doctor before taking prohormones and before combining grapefruit with any medication or dietary supplement.

Grapefruit Juice and CYP34A Enzyme

Grapefruit juice, as well as whole grapefruits and other products containing grapefruit, make it harder for your body to efficiently metabolize drugs or supplements such as prohormones. Grapefruit inhibits your body's CYP34A enzyme from breaking down medications, according to a report from the "New York Times" Health. Grapefruit juice may enhance the effectiveness of prohormones, as well as the danger. If your CYP34A enzyme doesn’t properly break down medication or supplements that enter your body, you may end up with a overdose of the substance in your body.

CYP34A Enzyme and Prohormones

Prohormones can increase the levels of testosterone, estrogen and progesterone in your body. Testosterone can increase your muscle mass and strength. It can also heighten aggression and sex drive, as well as an increase your chances of developing hair loss and acne. Consuming grapefruit with prohormones can elevate these effects. It can also elevate the risk of side effects from too much estrogen, such as an increase in fat gain and water weight. Other side effects include high blood pressure and liver damage. Combining grapefruit juice with prohormones increases your risk of such side effects.

Prohormones and Estrogen

Prohormones contain estrogen, just as birth control pills do. Grapefruit and grapefruit juice can cause life-threatening side effects if combined with birth control pills. Grapefruit makes it difficult for your body to metabolize estrogen, increasing your risk for the side effect of developing blood clots. Blood clots can cause gangrene, heart attacks and stroke. According to an article in "The Sun" in April 2009, a woman who followed a grapefruit diet for three days while also taking oral contraceptives nearly lost a leg to gangrene after developing a blood clot.


It doesn't take much grapefruit or grapefruit juice to slow your body's metabolism of prohormones and other supplements and medications. Drinking one glass of grapefruit juice may slow your body's absorption of medications by 47 percent, according to the Harvard Medical School Family Health Guide. The effect of grapefruit juice on your CYP34A enzyme wears off slowly. Even 24 hours after you ingest it, grapefruit juice may still inhibit metabolism of prohormones by more than 15 percent. Talk to your doctor before taking prohormones or combining grapefruit juice with any medication or supplement you take.

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