It may sound silly, but grapefruit juice is actually the most dangerous common food there is (I'm not including actual known poisonous foods or incorrectly chosen wild mushrooms) aside from foods that people actually have allergies to, such as peanuts and shellfish.

Grapefruit juice might be worse because its danger doesn't stem from an allergy, so people may not even know the problems they might be having are from the grapefruit juice they drank. I'll be making the case that it should actually be treated like a drug rather than a food. Why this is not more well-known, I'm not entirely sure, but it really should be common knowledge, even taught in schools, that grapefruit juice is a powerful substance equivalent to a drug, and definitely interacts with drugs in extremely powerful ways.

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The Good

Grapefruit juice contains several substances we would generally consider to be 'healthy'.Antioxidants known as naringin, naringenin, and hesperetin; and the furanocoumarin, bergapten(1) (2). These healthy substances are well-absorbed and bioavailable to the body even at the small doses present if one just drinks a glass of juice in the morning(3).

Antioxidants, such as these, can be extremely beneficial for various bodily functions, warding off age-related stress chemicals and even decreasing inflammation. In fact, one study found the naringenin in grapefruit to be one of the most powerful antioxidants for decreasing age-related brain inflammation that can lead to dementia (4). Another found that it was helpful in inhibiting pseudomonas aeruginosa, a dangerous pathogenic bacteria we discussed on our previous article Could Humans Be Trained to Diagnose Infection Based on Smell?.

The Bad

Most antioxidants seem to have beneficial qualities, and even the antioxidants in grapefruit juice are beneficial in some ways, as we pointed out above. But the flavenones in grapefruit juice have special qualities that can cause problems ranging from mildly problematic to downright deadly, and at doses that would be the equivalent to just a single glass.

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The Cytochrome P450 Enzyme System for the Biochemists Out There

Medication interactions cause the vast majority of these problems. Grapefruit juice causes an inhibition of the cytochrome P450 isoenzyme system the enzyme system that is responsible for the liver detoxification of a variety of drugs and even caffeine ⁽⁵⁾.

When Caffeine Is Your Drug of Choice

What this means is when you take a substance that is detoxified by this enzyme system, it may end up staying in your system much longer than studies show it should.

In the case of caffeine, it can delay the caffeine wearing off, and if you drink a certain amount of caffeine everyday, adding grapefruit juice could make you jittery, cause insomnia, or even cause heart palpitations.

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Some chronic users of grapefruit juice in the mornings may even be unconsciously taking advantage of this effect to make their caffeine last longer throughout the day! Before you try to extend your caffeine buzz with grapefruit juice, though, keep reading to ensure you understand the potential risks of doing so.

Beware if You Take Any Pharmaceuticals

In the case of pharmaceuticals, this predilection for making drugs last longer could lead to a specific dosage of a drug acting like a much larger dose, or it may act for a much longer time. Drug dosages are determined by how they act in the body, and include information about how the average person metabolizes the substance.

When the detoxification of a drug is inhibited, it could cause side effects, drug overdoses, and even death... just from the addition of grapefruit juice to the diet. This is not an overly dramatic statement, but the reality of 'using' the drug called grapefruit juice. Just a few examples of the interactions that can cause deadly interactions with grapefruit juice are:

• Cholesterol lowering statin drugs: a deadly condition of rapid muscle death called rhabdomyolysis can occur with atorvastatin, lovastatin, or simvastatin ⁽⁵⁾
• Blood pressure medications: taking the medications felodipine, nicardipine, nifedipine, nisoldipine, or nitrendipine can lead to serious low blood pressure issues. The drugs can reach maximum concentrations with the addition of grapefruit juice ⁽⁶⁾
• Oral antidiabetic medications: some medications can lead to serious issues of low blood sugar
• The blood thinner Coumadin: Can lead to severe bleeding. This drug must be very tightly controlled through regular blood testing, and grapefruit juice can destroy this tight regulation

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These are literally just a tiny number of hundreds upon hundreds of examples of problems that can occur with grapefruit juice, and these are just the deadly ones! There are so many interactions, and so many different reactions that could occur due to individual physiology, that it would be ridiculous to list individual drugs in a general information article such as this, as the list would simply be too long to benefit anyone.

And The Ugly

With tens of millions of people taking these drugs, the problems of grapefruit juice can affect almost anyone on any medication. It gets even worse because they don't know what, exactly, causes the problems. It's been widely thought the problem stems from naringenin, but at least one study has found that not to be the case ⁽⁹⁾. Also, different juices contain different levels of these antioxidants.

Therefore, any study that used fresh juice or naringenen isolates and came to the conclusion there was no drug interaction could be wrong. In other words, even if you do look up drug interactions and it's shown to be safe, it may not be.

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Even worse is that even in healthy people not taking drugs, grapefruit juice led to subtle heart electrical system changes known as QT Prolongation or Long QT Syndrome. QTS is the "...leading cause of mortality among young athletes." ⁽¹⁰⁾ and probably caused the deaths of marathon runner Jim Fixx, and Loyola basketball star Hank Gathers.

Needs a Warning Label

As you can see, grapefruit juice can actually be quite a dangerous substance, and since most people are simply not aware of these dangerous and deadly interactions, I think it should have a warning label! But since it doesn't, you can at least pass this along and help get this important information out to as many people as possible. Grapefruit juice really is a powerful drug, and should be treated as such.