Medically reviewed on June 11, 2018
Scientific Name(s): Humulus lupulus L. Family: Cannabaceae (marijuana family)
Common Name(s): Hops
Hops have been used for flavoring; hops and lupulin have been used as a digestive aid, for mild sedation, diuresis, and treating menstrual problems, but no clinical studies are available to confirm these uses.
Hops has been used as a mild sedative or sleep aid, with the dried strobile given in doses of 1.5 to 2 g. An extract combination with valerian, Ze 91019 ( ReDormin , Ivel ) has been studied at a hops dose of 60 mg for insomnia.
Contraindications have not yet been identified.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
There are no reported side effects when used in moderation.
Malignant hyperthermic reactions have been observed in dogs that consumed boiled hops residues. A wide safety margin for humans has been extrapolated from animal experiments.
Hops is a perennial climbing vine extensively cultivated worldwide. Male and female flowers are located on separate plants; the cone-shaped fruits are known as strobiles, which are collected in the fall and carefully dried.
Hops have been used for centuries to flavor and preserve beer. The bitter, aromatic taste of beer is mostly due to the hops content. Hops extracts are also used for other flavoring purposes in the food industry. Medical uses of hops and lupulin include aiding digestion, mild sedation, diuresis, and treating menstrual problems. Hops pickers have reported sedation during harvest, and hops flowers have been added to pillows for relief of nervous conditions.
The most characteristic constituents of hops are the bitter principles, known as alpha- and beta-acids. In the plant the alpha-acids occur as humulone, cohumulone, and adhumulone. 1 , 2 During the brewing process, these compounds are isomerized to the iso-alpha-acid series of compounds, that possess the bitter taste. 3 The beta-acid series of compounds include lupulone and congeners; 1 , 2 this series is destroyed during brewing. The relative proportions of the bitter acids affect the quality of the hops, and many methods have been developed for quantifying hop acids in different varieties, including nuclear magnetic resonance (NMR) 1 , 4 and high-pressure liquid chromatography (HPLC). 5 , 6 The complex profile of hop acids is dependent on genetics, cultivation, and storage conditions. Long-term storage of hops leads to major deterioration in quality.
The essential oils of hops are less characteristic but are still important to hop quality. Over 100 volatile compounds have been identified, with gas chromatography and gas chromatography-mass spectroscopy (GC-MS) being key techniques for analysis. 7 , 8 Caryophyllene, beta-myrcene, and humulene are the most abundant constituents of hops volatile oils.
A third group of hops constituents is the prenylflavonoids. Xanthohumol is the dominant prenylflavonoid of hops, 9 with 8-prenylnaringenin also of importance. 10 A GC-MS method has been developed for the latter, 10 while liquid chromatography-tandem mass spectrometry (LC-MS) has been used to directly quantify prenylflavonoids and their isomerization products in beer and hops extracts. 11 The variation in prenylflavonoids between hops varieties has also been studied. 12 The fate of xanthohumol as hops is processed into beer has been studied; 20% to 30% is converted to isoxanthohumol. 13 The metabolism of xanthohumol in rat and human liver microsomes has also been characterized. 14 , 15
Uses and PharmacologySedative
The observation that hops pickers often experienced sedation prompted investigation of hops for sedative principles.Animal data
The compound 2-methyl-3-buten-2-ol was isolated and found to reduce the spontaneous movement of rats when given intraperitoneally. 16 The small amounts found in hops 7 makes it unlikely that this compound completely explains hops sedation.Clinical data
8-prenylnaringenin was found to be a potent estrogen receptor agonist in estrogen-responsive cells, while other hops phenolics were less active (isoxanthohumol, 6-prenylnaringenin) or had no activity (xanthohumol). 20 The amounts present in beer were considered to be too small to cause estrogenic effects. Estrogenic effects in vivo were observed in mice given isolated 8-prenylnaringenin in drinking water at 100 mcg/mL, using uterine vascular permeability as an endpoint. 21Clinical data
Hops bitter acids have substantial effects on metabolic enzymes.Animal data
Colupulone adsorbed on brewers' yeast was found to induce cytochrome P-450 3A in mice, an enzyme capable of N-demethylation of ethylmorphine. 25 , 26 However, short-term assays for aflatoxin or benzpyrene activation through colupulone induction of CYP450 did not find a change in mutagen activation. 27 While beer and other alcoholic beverages have been found to inhibit mutagenesis induced by carcinogens in an Ames test, the compounds responsible were not identified. 28 In a later study, several hops prenylflavonoids inhibited carcinogenic amine activation by CYP1A2. 29
Humulone was identified as the active hops constituent that inhibited phorbol ester-induced inflammation in mice. 30 The same group later demonstrated that humulone was active in blocking tumor promotion in the classical two-stage model of carcinogenesis. 31 Several different hops prenylflavonoids demonstrated antiproliferative and cytotoxic effects in breast, colon, and ovarian human cancer cell lines. 32 8-prenylnaringenin was shown to upregulate the cadherin and catenin genes in human breast cancer cells. 33 A comprehensive evaluation of xanthohumol as a cancer chemopreventative agent found that it warented clinical investigation because it had distinct activities at the initiation, promotion, and progression stages of carcinogenesis. 34Clinical data
Research reveals no clinical data regarding the use of hops for cancer chemoprevention.Antibiotic and other
The hop bitter acids have antibacterial and antifungal activity important for the preservative function of hops in beer. When tested at the normal pH of beer (4.0), isohumulone inhibited bacterial growth at concentrations at which it is normally found in beer. 35 The prenylflavonoids of hops were shown to be more effective antioxidants than nonprenylated flavonoids. 36 Humulone potently suppressed COX-2 gene expression at the level of transcription. 37 Xanthohumols inhibited diacylglycerol acyltransferase, an effect of possible importance in lipid metabolism. 38 Polyphenolics of hops were shown to inhibit alpha-acid oxidase activity, thereby providing an internal control over hops' acid metabolism. 39 Hops proanthocyanidins were shown to inhibit neuronal nitric oxide synthetase and efficiently scavenge reactive nitrogen species. 40
Hops has been used as a mild sedative or sleep aid, with the dried strobile given in doses of 1.5 to 2 g. An extract combination with valerian, Ze 91019 ( ReDormin , Ivel ) has been studied at a hops dose of 60 mg for insomnia. 41
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Research reveals little or no information regarding adverse reactions with the use of hops.
As an historical food constituent, hops has “generally recognized as safe” (GRAS) status by the FDA, however; use of medicinal quantities of hops may pose more risk than common levels of exposure in food use. Dogs appear to be somewhat sensitive to hops compounds. A malignant hyperthermic reaction was observed in 5 dogs who consumed boiled hops residues used in home brewing. 42 A subchronic toxicity study of the hops alpha-acids was conducted in dogs; while high doses induced vomiting, the animals generally tolerated lower doses without ill effects. A wide safety margin for humans was extrapolated from this experiment. 43
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