Why Your Genes (and Even Herbs) Affect How You Process Medicine
From goldenseal to St. John’s Wort—how herbs can slow down, speed up, or completely change the way your body metabolizes medications.
If you've been following me for a while, you know I have a favorite enzyme (because, of course, I do)—the cytochrome P450 (CYP) superfamily. These enzymes do a lot behind the scenes, including breaking down herbs, medications, and other compounds we consume daily.
But here’s the thing: not everyone processes herbs the same way. Some people metabolize them too fast, while others break them down so slowly that effects become stronger — or even lead to side effects.
Why? Genetics, diet, and even other herbs or medications can influence your body’s ability to process them.
Meet the CYP450 Superfamily: The Body’s Chemical Processing Unit
CYP enzymes are found across almost all living organisms, from bacteria to humans. They’re named for their ability to absorb light at 450 nm and follow a standardized classification system. Humans have 57 CYP genes, but only 12 enzymes handle 70–80% of drug metabolism—including the infamous CYP2D6.
CYP2D6 is particularly important because it metabolizes medications used for pain relief, mental health, heart conditions, and even cancer treatment. However, not everyone processes drugs the same way — thanks to genetic variations in the CYP2D6 gene. Some people have no enzyme activity at all, while others break down medications so quickly that they barely work.
How Genetic Variations Affect Herb and Drug Metabolism
CYP2D6 variations create four metabolizer types:
Poor metabolizers (PM): Little to no enzyme activity → Higher herb or drug levels, more side effects
Intermediate metabolizers (IM): Reduced activity → Moderate processing
Normal metabolizers (NM): Expected enzyme function → Balanced breakdown
Ultrarapid metabolizers (UM): Excess enzyme function → Herbs and medications clear too quickly, reducing effectiveness
For example, if a poor metabolizer takes an antidepressant like vortioxetine, they’ll have 2.1 times higher drug levels than someone with normal metabolism—meaning they’re 5 times more likely to switch medications due to side effects (Frederiksen et al., 2022). Meanwhile, ultrarapid metabolizers clear the drug so fast that it may not work at all.
But here’s where things get even more complicated — it’s not just your genes that determine how your body processes medicine.
It’s Not Just Genetics—Herbs and Diet Play a Big Role
While genes set the baseline, they don’t tell the whole story. Non-genetic factors like diet, supplements, and even other medications can block or enhance CYP2D6 activity — a phenomenon called phenoconversion.
Common CYP2D6 Inhibitors That Affect Herb and Drug Metabolism
Medications: Fluoxetine, paroxetine, bupropion
Herbs & Compounds: Goldenseal, sesamin (found in sesame), curcumin
When someone takes a CYP2D6 inhibitor, their body processes herbs and drugs more slowly, even if their genes suggest otherwise. This can lead to higher concentrations in the body and unexpected side effects.
Why This Matters for Herbalists and Practitioners
The fact that common herbs and foods can significantly alter drug metabolism reinforces why herbalists, holistic practitioners, and even everyday consumers need to be aware of these interactions. Understanding these enzyme pathways isn’t just about science—it’s about real - world safety and effectiveness in herbal practice.
That brings us to a key question: how do we bridge the gap between genetic variability, herb-drug interactions, and practical herbalism?
How Herbs Can Speed Up or Slow Down Metabolism
Many herbal compounds influence CYP enzyme activity, sometimes in ways that increase the risk of interactions with prescription drugs.
For example:
Goldenseal (Hydrastis canadensis) is one of the strongest CYP2D6 inhibitors, meaning it slows drug metabolism, leading to higher drug concentrations in the bloodstream. If taken alongside antidepressants or opioids metabolized by CYP2D6, it could increase the risk of side effects like drowsiness, nausea, or even toxicity.
St. John’s Wort (Hypericum perforatum) has the opposite effect—it’s a CYP3A4 inducer, meaning it speeds up drug metabolism. This can make some medications (like birth control pills or blood thinners) less effective.
Curcumin (from turmeric) is a moderate CYP2D6 inhibitor, but it also interacts with other CYP enzymes, potentially affecting the breakdown of antidepressants, statins, and certain pain medications.
Sesamin (from sesame seeds) is another natural CYP2D6 inhibitor, which could have subtle but significant effects on metabolism if consumed in large amounts.
Even grapefruit juice can affect CYP enzymes—most notably CYP3A4, which processes about 50% of all medications. This is why some drug labels warn against drinking grapefruit juice, as it can increase drug levels in the blood, leading to stronger-than-expected effects.
Final Thoughts: The Future of Herbalism & Drug Metabolism
The more we learn about CYP enzymes, the better we can integrate herbalism with modern medicine. While herbs can absolutely support health, they also have powerful biochemical effects that can impact how the body processes medications.
In an ideal world, genetic testing would be easily accessible, giving us concrete answers about a person’s metabolizer status. But in reality, this isn’t always feasible or realistic to expect. That’s why understanding key herbs that affect CYP2D6 — and having a solid grasp of pharmacokinetics and pharmacodynamics of pharmaceuticals your clients may be taking — is crucial for both safety and effective herbal practice.
If a client is taking prescription medications and also using herbal supplements, it’s crucial to ask:
Does this herb affect CYP enzymes?
Could it slow or speed up metabolism?
How would this interfere with existing medication?
What do you think? Have you ever experienced unexpected side effects from a medication or herb? Let’s discuss in the comments!
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See you soon,
Agy
References
Taylor et al., 2020. The role of CYP450 enzymes in drug metabolism.
Kane, 2021. Genetic variations in CYP2D6 and their clinical implications.
Frederiksen et al., 2022. The impact of CYP2D6 genotype on vortioxetine metabolism.