Just some stuff about me.
Grapefruit Is One of the Weirdest Fruits on the Planet
Grapefruit is a mix between the pomelo—a base fruit—and a sweet orange, which itself is a hybrid of pomelo and mandarin.
The human body has mechanisms to break down stuff that ends up in the stomach. The one involved here is cytochrome P450, a group of enzymes that are tremendously important for converting various substances to inactive forms. Drugmakers factor this into their dosage formulation as they try to figure out what’s called the bioavailability of a drug, which is how much of a medication gets to your bloodstream after running the gauntlet of enzymes in your stomach.
Grapefruit has a high volume of compounds called furanocoumarins, which are designed to protect the fruit from fungal infections. When you ingest grapefruit, those furanocoumarins permanently take your cytochrome P450 enzymes offline. There’s no coming back. Grapefruit is powerful, and those cytochromes are donezo. So the body, when it encounters grapefruit, basically sighs, throws up its hands, and starts producing entirely new sets of cytochrome P450s. This can take over 12 hours.
This rather suddenly takes away one of the body’s main defense mechanisms. If you have a drug with 10 percent bioavailability, for example, the drugmakers, assuming you have intact cytochrome P450s, will prescribe you 10 times the amount of the drug you actually need, because so little will actually make it to your bloodstream. But in the presence of grapefruit, without those cytochrome P450s, you’re not getting 10 percent of that drug. You’re getting 100 percent. You’re overdosing.
Less than a single cup can be enough, and the effect doesn’t seem to change as long as you hit that minimum.
Here’s a brief and incomplete list of some of the medications that research indicates get screwed up by grapefruit:
Benzodiazepines (Xanax, Klonopin, and Valium) Amphetamines (Adderall and Ritalin) Anti-anxiety SSRIs (Zoloft and Paxil) Cholesterol-lowering statins (Lipitor and Crestor) Erectile-dysfunction drugs (Cialis and Viagra) Various over-the-counter meds (Tylenol, Allegra, and Prilosec) And about a hundred others.
This interaction, by the way, seems to affect all of the bitter citruses—the ones that inherited the telltale tang from the pomelo. Sour orange. Lime, too. But it’s unlikely that anyone would drink enough sour orange or lime juice to have this effect, given how sour it is. Grapefruit, on the other hand, is far more palatable in large doses.
there’s nothing inherently wrong with the fruit. There’s plenty of really helpful, healthy stuff in a grapefruit, especially vitamin C, which it has in spades.