Hops and their effect on human liver drug-processing enzymes
What it found
Hop extracts blocked several key liver enzymes that process medicines in lab tests using human tissue.
The strongest effects were seen on a group of enzymes called CYP2C.
What they found
Studies in people
Blood levels in people
The authors note two earlier studies in people where blood levels of the hop compound xanthohumol were measured. After single doses of 20, 60 or 180 mg given to 24 women and 24 men, peak blood levels were 33 mg/L, 48 mg/L or 120 mg/L.
Animal and lab studies
Blocking CYP2C enzymes
In lab tests using human liver tissue, the hop extract strongly blocked three enzymes called CYP2C8, CYP2C9 and CYP2C19. At a concentration of 5 μg/mL, it reduced their activity by 70% to 93%.
Weaker effect on CYP1A2
The same extract had a smaller effect on another enzyme, CYP1A2, reducing its activity by 27% at 5 μg/mL. However, one hop compound called xanthohumol caused this enzyme to lose activity over time in the lab tests.
No effect on some enzymes
Neither the hop extract nor the four individual hop compounds blocked three other liver enzymes called CYP3A4, CYP2D6 or CYP2E1 in these lab tests.
Most active hop compounds
Two specific compounds from hops were the strongest blockers. Isoxanthohumol was the most potent against CYP2C8, while 8-prenylnaringenin was the strongest against CYP1A2, CYP2C9 and CYP2C19.
What the authors conclude
- They say hop extracts can block certain liver enzymes that process many common medicines, especially those in the CYP2C family.
- They warn that taking hop supplements alongside prescription drugs could lead to higher drug levels in the blood and longer-lasting effects.
- The authors state that studies in people are needed to find out if these lab results actually matter in real life.
How it was done
Women often take hop supplements for menopause symptoms, and hops are used to brew beer. The authors wanted to know if hops could interfere with how the body breaks down prescription drugs.
They tested a standardised hop extract and four individual hop compounds on human liver enzymes in the lab. They used liver tissue pooled from 50 donors and measured how much each substance slowed down eight different enzymes.
What it can’t tell you
- These tests were done on liver tissue in a lab, not inside living people. Lab results cannot show exactly what happens when someone takes a hop supplement with medicine.
- Scientists do not yet know if the amounts of hop compounds that reach the blood after normal use are high enough to cause these effects in people.
Who paid
- Funding
- Funded by NCCIH NIH HHS (from the PubMed record).
- Authors work at
- University of Illinois College of Pharmacy, Illinois -
The paper
- Title
- Inhibition of human cytochrome P450 enzymes by hops (Humulus lupulus) and hop prenylphenols
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Yuan Y, Qiu X, Nikolić D, et al (2014). Inhibition of human cytochrome P450 enzymes by hops (Humulus lupulus) and hop prenylphenols. European journal of pharmaceutical sciences. doi:10.1016/j.ejps.2013.12.003Free full textPubMed 24342125DOI
Summary written 1 Oct 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error