Hops, derived from the plant Humulus lupulus, are widely recognized as a primary ingredient in brewing, providing beer with its characteristic flavor, aroma, and bitterness. Beyond brewing, the cones of the female hop plant have a long history in traditional medicine for their calming effects and sometimes for gynecological issues. Observed menstrual disturbances in female hop workers led to scientific inquiry into whether hops interact with the body’s hormonal system. Modern research confirms that hops possess hormonal activity through plant-derived compounds known as phytoestrogens. This discovery has made the hormonal effects of hops, and the question of whether they increase estrogen, a frequent subject of investigation.
Identifying the Potent Compound in Hops
The estrogenic activity of hops is attributed to several related molecules, but one prenylated flavonoid stands out as the most potent phytoestrogen identified in the plant kingdom. This compound is 8-Prenylnaringenin (8-PN). Although hops contain other prenylated flavonoids like xanthohumol and isoxanthohumol, 8-PN is the primary driver of the plant’s hormonal effects.
The concentration of 8-PN in the raw hop cone is relatively low, often more than ten times less abundant than xanthohumol. However, 8-PN can be formed from its precursor, isoxanthohumol (IX). This conversion occurs during thermal processing of the hops and through the action of certain gut bacteria after consumption. This metabolic pathway means that exposure to the active compound is not solely dependent on the initial amount of 8-PN in the hops.
The Mechanism of Estrogen Receptor Interaction
The hormonal action of 8-PN is defined by its classification as a phytoestrogen, a plant compound structurally similar enough to human estrogen to interact with the body’s estrogen receptors (ERs). Unlike the body’s own estrogen, 17\(\beta\)-estradiol, 8-PN acts as a natural Selective Estrogen Receptor Modulator (SERM). SERMs selectively activate or block estrogen receptors in different tissues, leading to varied effects throughout the body.
Human cells possess two main types of estrogen receptors: Estrogen Receptor-alpha (ER-\(\alpha\)) and Estrogen Receptor-beta (ER-\(\beta\)). While many other phytoestrogens, such as those found in soy, prefer ER-\(\beta\), 8-PN is distinct because it binds preferentially to ER-\(\alpha\). This affinity is significant because ER-\(\alpha\) is primarily associated with proliferative effects in tissues like the uterus and mammary gland, while ER-\(\beta\) often mediates opposing or regulatory functions.
The potency of 8-PN is a factor, as it can stimulate certain estrogen receptors up to a hundred times more effectively than genistein, a well-known soy phytoestrogen. Despite this high potency compared to other plant compounds, 8-PN is still considerably less potent than the body’s endogenous estrogen, 17\(\beta\)-estradiol, often estimated to be around 70 to 250 times weaker. When 8-PN binds to an estrogen receptor, it mimics the action of natural estrogen, leading to estrogenic activity.
Translating Research to Real-World Consumption
Whether hops increase estrogen in a meaningful way depends heavily on the concentration of 8-PN in the consumed product and its bioavailability. The most common source of hops exposure is beer, but the amount of 8-PN in commercially brewed beer is generally very low. Concentrations of 8-PN in most lagers and ales are often below detectable limits or are considered physiologically non-relevant, typically ranging from 1 to 240 micrograms per liter (\(\mu\)g/L).
The total dietary exposure is complex because the precursor isoxanthohumol (IX) is present in higher concentrations, often 10 to 40 times greater than 8-PN in beer. Since IX can be converted to the active 8-PN by intestinal bacteria, an individual’s gut microbiome and metabolic capacity influence the final absorbed amount. Even assuming efficient conversion, studies suggest that moderate beer consumption results in 8-PN exposure far below the levels required to produce detectable estrogenic effects in humans.
To reach the effective doses observed in animal studies, the required amount of beer consumption would be impractical, exceeding a thousand liters daily. Standardized hop extracts, unlike beer, are processed to concentrate the active prenylated flavonoids. This makes them the only consumption method capable of delivering a dose high enough to elicit a hormonal response, highlighting the separation between casual dietary intake and targeted therapeutic use.
Clinical Applications and Considerations
The estrogenic effect of hops is utilized in a controlled setting for therapeutic purposes, particularly in managing symptoms associated with menopause. Standardized extracts of hops are studied for their ability to alleviate vasomotor symptoms, such as hot flashes and night sweats, which result from the decline in natural estrogen levels. The use of these extracts provides a natural alternative for women seeking to manage these discomforts.
Clinical trials show that daily doses of concentrated hop extract, standardized for 8-PN, can significantly reduce the frequency of hot flashes. This application leverages the SERM-like activity of 8-PN to partially compensate for the lack of endogenous estrogen by interacting with the body’s estrogen receptors. These beneficial effects are achieved using concentrated, standardized supplements, not through the consumption of typical dietary sources like beer.