Hops, Phytoestrogens, and Supercritical CO2 Extraction: What Bitter Herbs for GLP-1 Really Contain

Hops is one of those herbs that seems to wear two different hats. Most people know it as the bitter, aromatic flower that gives beer its character, while anyone who has spent time reading about women’s health or menopause has probably seen hops listed alongside the famous botanical phytoestrogens. So when patients see hops listed inside a supplement built around appetite, fullness, and GLP-1, it is completely reasonable for them to pause and ask, “Is this going to affect my estrogen?”

Generally speaking, the answer depends less on the word “hops” on the label and more on which parts of the hop flower were actually extracted, how they were extracted, and what our own gut bacteria and liver do with those compounds once they are swallowed. This deep dive walks through the bitter taste receptors in the digestive tract, the chemistry inside the hop cone, how supercritical CO₂ extraction works, what feverfew adds to the picture, and who could benefit from individualized hormone and weight guidance before starting a GLP-1 targeted bitter-herb formula.

Bitter Taste Receptors Beyond the Tongue

Why the Gut “Tastes” Bitter Compounds

For a long time, bitter taste was thought of as a simple warning system on the tongue, a way to help us avoid spoiled or toxic foods. We now know that bitter taste receptors, called TAS2Rs (a family of roughly two dozen receptors that respond to bitter compounds), are also found throughout the digestive tract. Many of them sit on enteroendocrine cells (hormone-secreting cells lining the gut) that may play an important role in regulating energy intake and gut function.

When a bitter compound reaches those cells, it can trigger the release of several gut hormones that help coordinate the body’s response to a meal. The three that come up most often are GLP-1 (glucagon-like peptide-1), CCK (cholecystokinin, which helps signal the gallbladder and pancreas and contributes to fullness), and PYY (peptide YY, a hormone released further down the intestine that helps the brain register that a meal has been eaten). Additionally, these hormones slow how quickly the stomach empties and communicate with the brain through the vagus nerve, which is a large part of why a meal can leave us feeling satisfied rather than still searching the pantry.

How Natural GLP-1 Signaling Differs From GLP-1 Medications

It is worth making a clear distinction here, because the term GLP-1 now shows up everywhere. Prescription GLP-1 receptor agonists are engineered to activate the GLP-1 receptor directly and to stay active in the body far longer than the natural hormone does. Our own GLP-1, on the other hand, is released in short pulses around meals and is broken down within minutes.

If prescription GLP-1 medications act like pressing the brake pedal all the way to the floor and holding it there, bitter herbs could be thought of as tapping on the body’s own brake system right before a meal, nudging several gut hormones at once in a more modest and short-lived way. That difference matters. Bitter herbs are not a substitute for a medication when a medication is truly needed, and they are not expected to produce medication-sized effects; they are a way to support the signaling the body is already designed to use.

What Human Trials on Bitter Hop Extracts Have Shown

The most interesting human research in this area comes from a research group in New Zealand studying a standardized bitter hop extract. In a randomized, double-blind crossover trial of nineteen healthy-weight men, 500 mg of hop extract stimulated postprandial CCK, GLP-1, and PYY responses and reduced total food intake at lunch and an afternoon snack. Compared with placebo, total energy intake dropped by roughly 17 percent with both the stomach-release and the delayed, intestine-release capsules. Something important to note: the same study also reported small increases in nausea, bloating, and abdominal discomfort, and the participants did not report feeling less hungry on their appetite questionnaires, even though they ate less.

A longer trial was published in 2026. In this randomized, double-blind, placebo-controlled study, 150 adults with overweight or obesity took either placebo or 500 mg of a bitter hop extract daily for 24 weeks while attending monthly lifestyle-advice seminars, taking half of the dose at least an hour before their two main meals. Of the 128 participants who completed the program, the hop group lost 3.8 percent more body weight and 3.9 kg more fat mass than placebo, with no measured loss of skeletal muscle mass on bioelectrical impedance. The authors’ institute has licensed that particular extract to a supplement company, which is worth knowing when reading the results.

Unfortunately, it is easy to take numbers like these and paste them onto any product that contains hops. These trials tested one specific standardized extract at a specific dose and timing, so the results tell us the bitter-hop concept is biologically plausible and worth taking seriously, not that every hops formula will produce the same percentages.

Inside the Hop Cone: Bitter Acids vs. Phytoestrogens

The Soft Resins: Alpha Acids and Beta Acids

The hop cone (Humulus lupulus) contains small yellow glands called lupulin, and those glands hold most of the compounds people care about. The best known are the bitter acids found in the soft resins: alpha acids (humulones) and beta acids (lupulones). These are the compounds responsible for much of the bitterness of beer, and they are the compounds the bitter-hop appetite research has focused on. Chemically speaking, they are lipophilic, meaning they dissolve much more readily in oils and nonpolar solvents than they do in water.

The Prenylated Flavonoids: Xanthohumol, Isoxanthohumol, and 8-PN

Hops also contain a separate family of compounds called prenylated flavonoids (plant pigments with an added fat-loving side chain). The most abundant is xanthohumol, which converts to isoxanthohumol during brewing and processing. Hops also contain small amounts of 8-prenylnaringenin (8-PN, a potent plant-derived compound that can bind estrogen receptors). A 2019 review of hop compounds published in Nutrients describes 8-PN and 6-prenylnaringenin as among the most potent phytoestrogens found in hops, and notes that 8-PN is capable of binding both alpha and beta estrogen receptors.

This is where much of the confusion comes from. When hops are discussed as a phytoestrogen, the discussion is really about this flavonoid fraction, not the bitter acids. The two groups live in the same flower, but they behave very differently both chemically and in the body.

Why the Gut Microbiome and Liver Matter as Much as the Capsule

Here is an important thing to remember: what is in the capsule is not the whole story. Isoxanthohumol is considered a “pro-estrogen,” meaning it is fairly weak on its own but can be converted into the much stronger 8-PN. The same 2019 review explains that activation by intestinal microflora or cytochrome P450 enzymes yields 8-PN, and that isoxanthohumol can be metabolized in the human liver to form 8-PN.

Research published through the NIH shows how individual this conversion can be. In a study using a simulated human gut model and fecal samples from 51 women, isoxanthohumol passed unaltered through the stomach and small intestine and was converted to 8-PN in the distal colon, with up to 80 percent conversion. The women’s gut bacteria sorted into high (8 of 51), moderate (11 of 51), and slow (32 of 51) 8-PN producers, and the researchers estimated that this conversion could increase 8-PN exposure as much as tenfold in some people. In other words, two people taking the same hops product could end up with very different phytoestrogen exposure depending on their microbiome, which is one more reason we like to individualize recommendations rather than treat every patient the same.

How Supercritical CO₂ Extraction Works

Carbon Dioxide as a Tunable Solvent

Carbon dioxide becomes “supercritical” once it is held above roughly 31°C and about 74 bar of pressure (its critical point). In that state it behaves partly like a gas and partly like a liquid, which allows it to penetrate dried plant material easily while still dissolving certain compounds the way a liquid solvent would. When the pressure is released at the end of the process, the CO₂ simply returns to a gas and evaporates, leaving no chemical solvent residue behind in the extract.

The 2019 Nutrients review notes that CO₂ is a substitute for organic solvents of a highly nonpolar character, such as hexane and pentane, and that its use is largely limited to compounds of low polarity and low molecular weight. It also explains that supercritical CO₂ has become the industrial process of choice for producing brewery hop ingredients, typically run between 40 and 50°C and 150 to 400 bar. Ethanol, by contrast, is a polar solvent that dissolves a much broader range of hop compounds, including the polyphenols.

Why CO₂ Favors the Bitter Acids

Because the bitter acids are lipophilic and supercritical CO₂ behaves like a nonpolar solvent, CO₂ extraction naturally favors the soft resins and essential oils. Research published through the NIH describes commercial CO₂ hop extracts as containing nearly all essential oils in hops, a high ratio of alpha acids to beta acids, a small amount of hard resins, and minor traces of triglycerides, waxes, chlorophylls, and inorganic salts.

The same research team took the hops left over after CO₂ extraction and went looking for the flavonoids. After a first-stage extraction with pure supercritical CO₂ at 200 bar and 40 °C for three hours, a second stage using CO₂ modified with 80 percent ethanol at 50 °C and 25 MPa recovered up to 7.8 mg of flavonoids per gram of spent hops, mainly xanthohumol. That tells us two things at once. First, a meaningful amount of the flavonoid fraction stays behind in the plant material after pure CO₂ extraction. Second, the flavonoids were recovered once a polar co-solvent and higher pressure were added, so the extraction conditions matter a great deal.

“Solvent-Free” Does Not Automatically Mean “Phytoestrogen-Free”

This is the heart of the question if we are attempting to use hops as a GLP-1 bitter herb appetite aide, while also attempting to avoid the phytoestrogen effect that may not be clinically appropriate. A supercritical CO₂ hop extract is solvent-free in the sense that no hexane or other chemical solvent remains in the finished product. It is also selectively enriched for bitter acids, which is exactly what you would want in a bitter-herb formula. However, selective reduction is different from verified absence. Unless a manufacturer publishes testing showing undetectable xanthohumol, isoxanthohumol, and 8-PN in the finished extract, the most honest way to describe a CO₂ hops extract is “lower in prenylflavonoids than whole hops or an ethanol extract,” not “free of phytoestrogens.”

Additionally, as we discussed above, small amounts of isoxanthohumol can be amplified by gut bacteria in some individuals. That is why a sensible caution on the label for estrogen-sensitive conditions is not a contradiction of the extraction method; it is simply good clinical humility.

What Feverfew and Parthenolide Contribute

Parthenolide and the TAS2R4 Bitter Receptor

Feverfew (Tanacetum parthenium) is a member of the daisy family best known for its traditional use around headaches, and its signature compound is parthenolide, a sesquiterpene lactone (a bitter plant compound common in the daisy family). Newer research has looked at parthenolide as a bitter-receptor activator. In a 2026 cell study published in Molecular and Cellular Biochemistry, researchers screened bitter-compound databases and found that parthenolide binds the bitter receptor TAS2R4 and promotes GLP-1 secretion in a dose-dependent manner in human Caco-2 intestinal cells, working through a calcium-dependent signaling cascade that also involves the TRPM5 channel.

That is a promising mechanism, and it gives a logical reason to pair feverfew with hops. It is also important to remember that this was a cell-culture study; we do not yet have human trials showing that oral feverfew changes GLP-1 levels or appetite.

Laboratory Estrogen Receptor Findings vs. Real-World Dosing

Feverfew has also shown up in estrogen research. In a study published in Menopause examining seventeen herbs used by Costa Rican women for menopausal symptoms, a feverfew extract bound estrogen receptors and induced estrogen-responsive genes in MCF-7 breast cancer cells through ER-alpha. The authors concluded that studies of safety and efficacy are still needed before herbs like these are used as alternatives to hormone therapy.

Generally speaking, a plant extract binding a receptor in a dish is not the same as a measurable estrogenic effect from an oral capsule in a person, since digestion, absorption, dose, and metabolism all change the picture. That said, when two herbs in one formula both have some laboratory estrogen-receptor activity, it makes sense to keep the estrogen-sensitive caution firmly in place.

Practical Feverfew Considerations

• Daisy family allergy: anyone allergic to ragweed, chamomile, chrysanthemum, or other Asteraceae plants could react to feverfew.
• Blood thinners and antiplatelet medications: feverfew has traditionally been flagged for possible effects on platelet activity, so we prefer to review it alongside warfarin, aspirin, clopidogrel, and similar medications.
• Pregnancy and breastfeeding: feverfew has historically been avoided during pregnancy, and the formula is not intended for pregnancy or lactation.

Putting the GLP-1 Bitter Complex Label in Perspective

MediHerb’s GLP-1 Bitter Complex is a good real-world example of everything discussed above, so it is worth looking closely at what the label actually provides in each softgel.

At a glance: Hops

• Form: 218.2 mg supercritical CO₂ hops extract
• Standardized to: 89.4 mg alpha acids and 48 mg beta acids
• What that means: roughly 63 percent of the extract by weight is bitter acids, the fraction studied for gut hormone signaling

At a glance: Feverfew

• Form: 133.3 mg feverfew extract
• Standardized to: 2 mg parthenolide
• What that means: a consistent amount of the bitter compound studied for TAS2R4 activation

The suggested use is one softgel three times per day before meals, which fits the research model of delivering bitter compounds shortly before food arrives. The extraction choice lines up with the chemistry: concentrating alpha and beta acids gives the gut a meaningful bitter signal while generally leaving behind much of the flavonoid fraction. At the same time, the label still advises caution for anyone with a past or present estrogen-sensitive condition or using hormone replacement therapy, and it is not intended for pregnancy, lactation, or people under 18. In our office, we view that caution as the right clinical guardrail, for all of the reasons above.

Who Needs Individualized Hormone and Weight Guidance First?

Bitter herbs are simple, but the people who are most interested in them often have the most complicated hormone pictures. We prefer to take a closer look before starting a hops and feverfew formula for anyone who:

• has a personal history of breast, uterine, cervical, ovarian, or prostate cancer, or another estrogen-sensitive condition
• has endometriosis, uterine fibroids, or a strong family history of hormone-related cancers
• is using hormone replacement therapy, bioidentical hormones, hormonal birth control, or medications that block estrogen
• is perimenopausal or postmenopausal and already juggling hot flashes, sleep disruption, and weight changes
• is taking a prescription GLP-1 medication, diabetes medication, or blood thinner
• has a sensitive digestive tract, reflux, or a history of ulcers, since bitter compounds increase digestive activity
• is pregnant, trying to conceive, or breastfeeding

None of these automatically rule a bitter formula out. They simply mean the decision deserves a conversation, and sometimes lab work, rather than a guess.

How We Personalize Appetite, Weight, and Hormone Care

In a perfect world, our meals would contain enough protein and fiber, our sleep would be consistent, and our stress would stay low enough that our natural fullness signals could do their job. Unfortunately, late nights, skipped meals, chronic stress, and hormonal shifts all blunt those signals, and that is usually where cravings and stubborn weight begin.

At The Hayden Institute, we look at the whole picture before recommending any single product. Our functional endocrinology work evaluates thyroid, adrenal, blood sugar, and sex hormone patterns, while our clinical nutrition care focuses on food quality, digestion, and nutrient needs. For patients whose main goal is body composition, our weight loss support is individualized rather than one-size-fits-all. A bitter-herb formula could be considered as one tool within that plan, timed with meals and paired with protein, fiber, movement, and sleep, for the patients whose history makes it a good fit.

If you would like a simpler overview of how bitter herbs relate to GLP-1 and satiety, our companion article, Can Bitter Herbs Support Natural GLP-1 and Satiety Signaling?, is a good place to start.

Hops, Phytoestrogens, and Making an Informed Choice

Hops really does wear two hats. Its bitter acids are the compounds that have shown the most promise for gut hormone signaling and appetite, while its prenylated flavonoids are the reason hops earned its reputation as a phytoestrogen. Supercritical CO₂ extraction leans heavily toward the bitter acids and leaves no chemical solvent behind, which is a thoughtful formulation choice. However, “solvent-free” is not the same as “phytoestrogen-free,” and our gut bacteria and liver can change how much 8-PN we are ultimately exposed to.

Feverfew adds a second bitter signal with promising early research behind it, along with its own considerations for allergies and medications. For most people, a well-designed bitter formula could be a helpful companion to good habits, and for some people, it is worth checking hormone history first.

If you are in Northwest Houston or Cypress and are curious whether bitter herbs fit into your appetite, weight, or hormone plan, schedule a new-patient visit and our team will help you sort out what makes sense for you.