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If you look closely at the labeling on your favorite CBD tincture or gummy, you may have noticed the following warning:
Consult your doctor before use if you have been advised against eating grapefruit. Discontinue use if any adverse reactions occur.
While for some people, this might be the first time they’ve ever seen this warning label, it’s actually a statement that is found on several types of medications. We’re here to explain what the grapefruit disclaimer means and why it’s important.
Why does it matter if I eat grapefruit?
Maybe you just had a grapefruit juice at breakfast, or maybe your favorite citrus is a pomelo. Is this warning specific to one type of grapefruit? And does it matter how much grapefruit you’ve eaten?
Grapefruit and some of its close citrus fruit relatives including Pomelos, Seville oranges, tangelos, and limes contain a compound called furanocoumarins, a class of chemicals that disrupt the way your body breaks down medications.¹ Grapefruits are the fruit that has been studied the most in terms of interactions with various drugs, but the same rules should apply to the fruits listed above.
What does grapefruit have to do with CBD?
Interestingly, furanocoumarins and CBD are both able to disrupt the body’s way of metabolizing medication in similar ways.² While this isn’t an issue for most medications, if you’ve ever been advised by a doctor to avoid grapefruit or you have a medication that has a grapefruit warning, you should consult with your doctor before taking CBD.
How does grapefruit interact with medications?
The compound in grapefruits, furanocoumarin, isn’t interacting with your medication. It’s actually interacting with the enzymes in your gut that control the way your medication is absorbed.
Your body relies on the liver and small intestine to metabolize everything you ingest, and these organs rely on a class of proteins known as the cytochrome P450s, or CYPs to get this done.³ When you take medications, CYPs zoom around your intestinal tract to slow down the rate at which the active ingredients in these medications move from your gut to your bloodstream.
CYPs basically reduce the number of medications that are absorbed by the body (part of first-pass metabolism) and have an effect.
Furanocoumarins disrupt CYPs, making them less effective at controlling the way that metabolites are absorbed into the bloodstream. With fewer CYPs at work, the active ingredients in medications move into the bloodstream at much higher rates.
It doesn’t take much for the furanocoumarins in grapefruit to mess with your CYPs. Even a single grapefruit or glass of grapefruit juice can facilitate an interaction. On top of that, after you’ve had grapefruit, it can take anywhere from one to three days for your body to expel all levels of furanocoumarins.⁴ So even if you ate a grapefruit three days ago, there could still be lingering furanocoumarin levels in your bloodstream affecting your CYP levels.
What medications could be affected by CBD?
CYPs play a major role in metabolizing medication and other substances that pass through your liver, so any disruption to their normal functioning will lead to significant increases in the amount of a substance that ends up in your bloodstream—perhaps more than you or your doctor intended.
Importantly, most medications are safe to use with grapefruit. Such medications aren’t necessarily harmful when they are absorbed at higher levels into the body. This tells us that most medications are perfectly safe to be taken with CBD.
But certain medications can be very dangerous at higher levels. These include medications for cholesterol, blood pressure, and other heart conditions. Certain blood thinners and statins, for instance, come with the grapefruit warning on the label.⁵ If you’ve been advised to avoid grapefruit, you should talk with your doctor about whether it is safe for you to take CBD simultaneously with your other medications.
We should note that this applies primarily to edible and tincture varieties of CBD. If you are using topical CBD (which tends to absorb at the muscular level and doesn’t move into the bloodstream as readily), there is less risk of CBD-CYP interaction.
Bottom line: grapefruit and CBD
Grapefruits contain a compound that leads to significantly increased levels of medication in your bloodstream. While most medications are safe to use with grapefruit, there are a few that can have serious side effects when absorbed at higher than usual levels.
Several studies have shown that CBD is similar to furanocoumarin in its ability to inhibit or decrease the activity, of CYPs. While there haven’t been enough studies to determine what the implications of CBD’s CYP-inhibiting effects are, it’s clear that CBD interacts with CYPs in a significant way.
If you’ve never had to worry about grapefruit intake, then you shouldn’t have to worry about CBD interacting with any of your medications. (Just continue to be mindful of your serving size and monitor whether it’s delivering the functional benefits you’re looking for!)
If you have concerns about grapefruit or CBD interacting with your medications, check with your doctor or pharmacist to see if any of the medications you’ve been prescribed are known to interact with furanocoumarins. If the answer is yes but you still want to use CBD, stick with topical CBD or work with your doctor to find the right low dose of CBD that works for you.
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SOURCES:
¹Hung, W. L., Suh, J. H., & Wang, Y. (2017). Chemistry and health effects of furanocoumarins in grapefruit. Journal of food and drug analysis, 25(1), 71–83. https://doi.org/10.1016/j.jfda.2016.11.008
²Stout, S. M., & Cimino, N. M. (2014). Exogenous cannabinoids as substrates, inhibitors, and inducers of human drug metabolizing enzymes: a systematic review. Drug metabolism reviews, 46(1), 86–95. https://doi.org/10.3109/03602532.2013.849268
³Manikandan, P., & Nagini, S. (2018). Cytochrome P450 Structure, Function and Clinical Significance: A Review. Current drug targets, 19(1), 38–54. https://doi.org/10.2174/1389450118666170125144557
⁴Brickl, R., Schmid, J., & Koss, F. W. (1984). Clinical pharmacology of oral psoralen drugs. Photo-dermatology, 1(4), 174–186.
⁵Seden, K., Dickinson, L., Khoo, S., & Back, D. (2010). Grapefruit-drug interactions. Drugs, 70(18), 2373–2407. https://doi.org/10.2165/11585250-000000000-00000