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Hops

Scientific Name(s): Humulus lupulus L.
Common Name(s): Hops

Clinical Overview

Use

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.

Dosing

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

Contraindications have not yet been identified.

Pregnancy/Lactation

Avoid use. In vitro antispasmodic activity on the uterus has been documented.

Interactions

None well documented.

Adverse Reactions

There are no reported side effects when used in moderation.

Toxicology

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.

Botany

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.1, 2

History

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.2, 3 Use of hops for the treatment of mood disturbances, such as restlessness, anxiety, and sleep disturbances, is approved in the German Commission E Monographs.4

Chemistry

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.5, 6 During the brewing process, these compounds are isomerized to the iso-alpha-acid series of compounds, that possess the bitter taste.7 The beta-acid series of compounds include lupulone and congeners;5, 6 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)5, 8 and high-pressure liquid chromatography (HPLC).9, 10 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.11, 12 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,13 with 8-prenylnaringenin also of importance.14 A GC-MS method has been developed for the latter,14 while liquid chromatography-tandem mass spectrometry (LC-MS) has been used to directly quantify prenylflavonoids and their isomerization products in beer and hops extracts.15 The variation in prenylflavonoids between hops varieties has also been studied.16 The fate of xanthohumol as hops is processed into beer has been studied; 20% to 30% is converted to isoxanthohumol.17 The metabolism of xanthohumol in rat and human liver microsomes has also been characterized.18, 19

Uses and Pharmacology

CNS effects

Animal data

The compound 2-methyl-3-buten-2-ol was isolated and found to reduce the spontaneous movement of rats when given intraperitoneally.20 The small amounts found in hops11 makes it unlikely that this compound completely explains hops sedation. A review of animal studies reports equivocal findings for sedative effects of hops.21

Clinical data

Hops is often included in combination with valerian in sleep aids.22, 23, 24, 25

A randomized, placebo-controlled clinical trial evaluated 100 mg H. lupulus prepared in combination with soya and cade oil and soya lecithin in 101 patients with chronic primary insomnia. No difference over placebo was found.26 A smaller clinical study (n=17 nurses working shifts) evaluated the use of nonalcoholic beer containing hops and reported improved measures including actimeter-measured sleep latency and self-evaluated sleep anxiety.27

Phytoestrogenic

Animal 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).28 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.29, 30

Clinical data

Estrogenic effects were also observed in evaluation of hops extract for the treatment of menstrual symptoms.31 A double-blind, randomized, placebo-controlled, crossover trial conducted in 36 women experiencing symptoms of natural menopause were treated with hop extract capsules (standardized to 8-prenylnaringenin at 100 mcg/day) or placebo daily for 16 weeks to investigate relief of menopausal discomforts. Both objective and subjective outcomes were measured. At 8 weeks, both the treatment and placebo groups experienced significant improvements compared to baseline; however, after the crossover, the treatment group continued to experience significant improvements in all outcome measures over the next 8 weeks, whereas all scores worsened slightly in the placebo group.32 Reviews of studies have been published.21, 30, 33 (Karabin Zanoli, keiler) Use of hops in breast enhancement products was cause for concern.34, 35

Cancer chemoprevention

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.36, 37 However, short-term assays for aflatoxin or benzpyrene activation through colupulone induction of CYP450 did not find a change in mutagen activation.38 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.39 In a later study, several hops prenylflavonoids inhibited carcinogenic amine activation by CYP1A2.40

Humulone was identified as the active hops constituent that inhibited phorbol ester-induced inflammation in mice.41 The same group later demonstrated that humulone was active in blocking tumor promotion in the classical two-stage model of carcinogenesis.42 Several different hops prenylflavonoids demonstrated antiproliferative and cytotoxic effects in breast, colon, ovarian, renal, and prostate human cancer cell lines.43, 44, 30 8-prenylnaringenin was shown to upregulate the cadherin and catenin genes in human breast cancer cells.45 A comprehensive evaluation of xanthohumol as a cancer chemopreventative agent found that it warranted clinical investigation because it had distinct activities at the initiation, promotion, and progression stages of carcinogenesis.46

Clinical data

Research reveals no clinical data regarding the use of hops for cancer chemoprevention.

Other uses

The hop bitter acids have antibacterial and antifungal activity important for the preservative function of hops in beer.21(Zanoli) When tested at the normal pH of beer (4.0), isohumulone inhibited bacterial growth at concentrations at which it is normally found in beer.47 Polyphenols derived from hops reportedly reduced regrowth of dental plaque in a clinical study.48

The prenylflavonoids of hops were shown to be more effective antioxidants than nonprenylated flavonoids.49 Hops proanthocyanidins inhibited neuronal nitric oxide synthetase and efficiently scavenged reactive nitrogen species.50

Humulone potently suppressed COX-2 gene expression at the level of transcription.30, 51 (Karabin) Anti-inflammatory effects have been demonstrated for hops evaluated in knee osteoarthritis.52 (Hall) Xanthohumols inhibited diacylglycerol acyltransferase, an effect of possible importance in lipid metabolism.53 A clinical trial (n= 200) reported positive effects of matured hop extract in reducing body fat in healthy overweight trial participants.54 Limited studies suggest efficacy of hops extracts in preventing histamine release and reducing allergic symptoms.30, 55

Dosing

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.56

Pregnancy / Lactation

Avoid use. In vitro antispasmodic activity on the uterus has been documented.3

Interactions

None well documented. Flavonoids reportedly possess anticoagulant and antiplatelet activity.30

Adverse Reactions

Research reveals little or no information regarding adverse reactions with the use of hops.

Toxicology

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.57 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. 58

The LD50 for orally administered hop extract or lupulones in mice is approximately 500 to 3,500 mg/kg.3, 21

References

1. Humulus lupulus. USDA, NRCS. 2016. The PLANTS Database (http://plants.usda.gov, December 2016). National Plant Data Team, Greensboro, NC 27401-4901 USA
2. Khan IA, Abourashed EA. Leung's Encyclopedia of Common Natural Ingredients Used in Food, Drugs, and Cosmetics. 3rd ed. Hoboken, N.J.: Wiley; 2009.
3. Duke JA. Handbook of Medicinal Herbs. 2nd ed. Boca Raton, FL: CRC Press; 2003.
4. Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Integrative Medicine Communications; 2000.
5. Hoek AC, Hermans-Lokkerbol ACJ, Verpoorte R. An improved NMR method for the quantification of alpha-acids in hops and hop products. Phytochem Anal. 2001;12:53-57.11704962
6. Carson JF. The structure of humulone and lupulone as revealed by ozonization. J Am Chem Soc. 1951;73:4652-4654.
7. Carson JF. The alkaline isomerization of humulone. J Am Chem Soc. 1952;74:4615-4620.
8. Molyneux RJ, Wong Y. Nuclear magnetic resonance spectroscopic determination of alpha- and beta-acid homolog composition in hops. J Agric Food Chem. 1975;23:1201-1204.
9. De Cooman L, Everaert E, De Keukeleire D. Quantitative analysis of hop acids, essential oils, and flavonoids as a clue to the identification of hop varieties. Phytochem Anal. 1998;9:145-150.
10. Hampton R, Nickerson G, Whitney P, Haunold A. Comparative chemical attributes of native North American hop, Humulus lupulus var. lupuloides E. Small. Phytochemistry. 2002;61:855-862.12453579
11. Eri S, Khoo BK, Lech J, Hartman TG. Direct thermal desorption-gas chromatography and gas chromatography-mass spectrometry profiling of hop (Humulus lupulus L.) essential oils in support of varietal characterization. J Agric Food Chem. 2000;48:1140-1149.10775363
12. Steinhaus M, Scheiberle P. Comparison of the most odor-active compounds in fresh and dried hop cones (Humulus lupulus L. variety spalter select) based on GC-olfactometry and odor dilution techniques. J Agric Food Chem. 2000;48:1776-1783.10820094
13. Stevens JF, Ivancic M, Hsu VL, Deinzer ML. Prenylflavonoids from Humulus lupulus. Phytochem. 1997;44:1575-1585.
14. Tekel' J, De Keukeleire D, Rong H, Daeseleire E, Van Peteghem C. Determination of the hop-derived phytoestrogen, 8-prenylnaringenin, in beer by gas chromatography/mass spectrometry. J Agric Food Chem. 1999;47:5059-5063.10606572
15. Stevens JF, Taylor AW, Deinzer ML. Quantitative analysis of xanthohumol and related prenylflavonoids in hops and beer by liquid chromatography-tandem mass spectrometry. J Chromatogr A. 1999;832:97-107.10070768
16. Stevens JF, Taylor AW, Nickerson GB, et al. Prenylflavonoid variation in (Humulus lupulus): distribution and taxonomic significance of xanthogalenol and 4′-O-methylxanthohumol. Phytochemistry. 2000;53:759-775.10783982
17. Stevens JF, Taylor AW, Clawson JE, Deinzer ML. Fate of xanthohumol and related prenylflavonoids from hops to beer. J Agric Food Chem. 1999;47:2421-2428.10794646
18. Yilmazer M, Stevens JF, Deinzer ML, Buhler DR. In vitro biotransformation of xanthohumol, a flavonoid from hops (Humulus lupulus), by rat liver microsomes. Drug Metab Dispos. 2001;29:223-231.11181488
19. Yilmazer M, Stevens JF, Buhler DR. In vitro glucuronidation of xanthohumol, a flavonoid in hop and beer, by rat and human liver microsomes. FEBS Lett. 2001;491:252-256.11240137
20. Wohlfart R, Hänsel R, Schmidt H. The sedative-hypnotic action of hops. 4. Pharmacology of the hop substance 2-methyl-3-buten-2-ol (in German). Planta Med. 1983;48:120-123.6611749
21. Zanoli P, Zavatti M. Pharmacognostic and pharmacological profile of Humulus lupulus L. J Ethnopharmacol. 2008;116(3):383-396.18308492
22. Vonderheid-Guth B, Todorova A, Brattström A, Dimpfel W. Pharmacodynamic effects of valerian and hops extract combination (Ze 91019) on the quantitative-topographical EEG in healthy volunteers. Eur J Med Res. 2000;5:139-144.10799347
23. Fussel A, Wolf A, Brattsröm A. Effect of a fixed valerian-Hop extract combination (Ze 91019) on sleep polygraphy in patients with non-organic insomnia: a pilot study. Eur J Med Res. 2000;5:385-390.11003973
24. Müller CE, Schumacher B, Brattsröm A, Abourashed EA, Koetter U. Interactions of valerian extracts and a fixed valerian-hop extract combination with adenosine receptors. Life Sci. 2002;71:1939-1949.12175708
25. Salter S, Brownie S. Treating primary insomnia - the efficacy of valerian and hops. Aust Fam Physician. 2010;39(6):433-437.20628685
26. Cornu C, Remontet L, Noel-Baron F, et al. A dietary supplement to improve the quality of sleep: a randomized placebo controlled trial. BMC Complement Altern Med. 2010;10:29.20569455
27. Franco L, Sánchez C, Bravo R, et al. The sedative effect of non-alcoholic beer in healthy female nurses. PLoS One. 2012;7(7):e37290.22815680
28. Milligan SR, Kalita JC, Heyerick A, Rong H, De Cooman L, De Keukeleire D. Identification of a potent phytoestrogen in hops (Humulus lupulus L.) and beer. J Clin Endocrinol Metab. 1999;84:2249-2252.10372741
29. Milligan SR, Kalita JC, Pocock V, et al. The endocrine activities of 8-prenylnaringenin and related hop (Humulus lupulus L.) flavonoids. J Clin Endocrinol Metab. 2000;85:4912-4915.11134162
30. Karabin M, Hudcova T, Jelinek L, Dostalek P. Biotransformations and biological activities of hop flavonoids. Biotechnol Adv. 2015;33(6 pt 2):1063-1090.25708386
31. Coldham NG, Sauer MJ. Identification, quantitation and biological activity of phytoestrogens in a dietary supplement for breast enhancement. Food Chem Toxicol. 2001;39:1211-1224.11696395
32. Erkkola R, Vervarcke S, Vansteelandt S, Rompotti P, De Keukeleire D, Heyerick A. A randomized, double-blind, placebo-controlled, cross-over pilot study on the use of a standardized hop extract to alleviate menopausal discomforts. Phytomedicine. 2010;17(6):389-396.20167461
33. Keiler AM, Zierau O, Kretzschmar G. Hop extracts and hop substances in treatment of menopausal complaints. Planta Med. 2013;79(7):576-579.23512496
34. Milligan S, Kalita J, Pocock V, et al. Oestrogenic activity of the hop phyto-oestrogen, 8-prenylnaringenin. Reproduction. 2002;123:235-242.11866690
35. Liu J, Burdette JE, Xu H, et al. Evaluation of estrogenic activity of plant extracts for the potential treatment of menopausal symptoms. J Agric Food Chem. 2001;49:2472-2479.11368622
36. Mannering GJ, Shoeman JA, Deloria LB. Identification of the antibiotic hops component, colupulone, as an inducer of hepatic cytochrome P-4503A in the mouse. Drug Metab Dispos. 1992;20:142-147.1352202
37. Mannering GJ, Shoeman JA, Shoeman DW. Effects of colupulone, a component of hops and brewers yeast, and chromium on glucose tolerance and hepatic cytochrome P450 in nondiabetic and spontaneously diabetic mice. Biochem Biophys Res Commun. 1994;200:1455-1462.8185600
38. Shipp EB, Mehigh CS, Helferich WG. The effect of colupulone (a HOPS beta-acid) on hepatic cytochrome P-450 enzymatic activity in the rat. Food Chem Toxicol. 1994;32:1007-1014.7959454
39. Arimoto-Kobayashi S, Sugiyama C, Harada N, Takeuchi M, Takemura M, Hayatsu H. Inhibitory effects of beer and other alcoholic beverages on mutagenesis and DNA adduct formation induced by several carcinogens. J Agric Food Chem. 1999;47:221-230.10563876
40. Miranda CL, Yang Y, Henderson MC, et al. Prenylflavonoids from hops inhibit the metabolic activation of the carcinogenic heterocyclic amine 2-amino-3-methylimidazo[4, 5-f]quinoline, mediated by cDNA-expressed human CYP1A2. Drug Metab Dispos. 2000;28:1297-1302.11038156
41. Yasukawa K, Yamaguchi A, Arita J, Sakurai S, Ikeda A, Takido M. Inhibitory effect of edible plant extracts on 12-O-tetradecanoylphorbol-13-acetate-induced ear edema in mice. Phytother Res. 1993;7:185-189.
42. Yasukawa K, Takeuchi M, Takido M. Humulon, a bitter in the hop, inhibits tumor promotion by 12-O- tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mouse skin. Oncology. 1995;52:156-158.7854777
43. Miranda CL, Stevens JF, Helmrich A, et al. Antiproliferative and cytotoxic effects of prenylated flavonoids from hops (Humulus lupulus) in human cancer cell lines. Food Chem Toxicol. 1999;37:271-285.10418944
44. Busch C, Noor S, Leischner C, et al. Anti-proliferative activity of hop-derived prenylflavonoids against human cancer cell lines. Wien Med Wochenschr. 2015;165(11-12):258-61.25925225
45. Rong H, Boterberg T, Maubach J, et al. 8-Prenylnaringenin, the phytoestrogen in hops and beer, upregulates the function of the E-cadherin/catenin complex in human mammary carcinoma cells. Eur J Cell Biol. 2001;80:580-585.11675933
46. Gerhauser C, Alt A, Heiss E, et al. Cancer chemopreventive activity of xanthohumol, a natural product derived from hop. Mol Cancer Ther. 2002;1:959-969.12481418
47. Simpson WJ, Smith AR. Factors affecting antibacterial activity of hop compounds and their derivatives. J Appl Bacteriol. 1992;72:327-334.1517174
48. Shinada K, Tagashira M, Watanabe H, et al. Hop bract polyphenols reduced three-day dental plaque regrowth. J Dent Res. 2007;86(9):848-851.17720853
49. Rodriguez RJ, Miranda CL, Stevens JF, Deinzer ML, Buhler DR. Influence of prenylated and non-prenylated flavonoids on liver microsomal lipid peroxidation and oxidative injury in rat hepatocytes. Food Chem Toxicol. 2001;39:437-445.11313109
50. Stevens JF, Miranda CL, Wolthers KR, Schimerlik M, Deinzer ML, Buhler DR. Identification and in vitro biological activities of hop proanthocyanidins: inhibition of nNOS activity and scavenging of reactive nitrogen species. J Agric Food Chem. 2002;50:3435-3443.12033808
51. Yamamoto K, Wang J, Yamamoto S, Tobe H. Suppression of cyclooxygenase-2 gene transcription by humulon of beer hop extract studied with reference to glucocorticoid. FEBS Lett. 2000;465:103-106.10631313
52. Hall AJ, Babish JG, Darland GK, et al. Safety, efficacy and anti-inflammatory activity of rho iso-alpha-acids from hops. Phytochemistry. 2008;69(7):1534-1547.18358504
53. Tabata N, Ito M, Tomoda H, Ōmura S. Xanthohumols, diacylglycerol acyltransferase inhibitors, from Humulus lupulus. Phytochemistry. 1997;46:683-687.9366096
54. Morimoto-Kobayashi Y, Ohara K, et al. Matured hop extract reduces body fat in healthy overweight humans: a randomized, double-blind, placebo-controlled parallel group study. Nutr J. 2016;15:25.26960416
55. Segawa S, Takata Y, Wakita Y, et al. Clinical effects of a hop water extract on Japanese cedar pollinosis during the pollen season: a double-blind, placebo-controlled trial. Biosci Biotechnol Biochem. 2007;71(8):1955-1962.17690485
56. Fussel A, Wolf A, Brattstrom A. Effect of a fixed valerian-hop extract combination (Ze 91019) on sleep polygraphy in patients with non-organic insomnia: a pilot study. Eur J Med Res. 2000;5:385-390.11003973
57. Duncan KL, Hare WR, Buck WB. Malignant hyperthermia-like reaction secondary to ingestion of hops in five dogs. J Am Vet Med Assoc. 1997;210:51-54.8977648
58. Chappel CI, Smith SY, Chagnon M. Subchronic toxicity study of tetrahydroisohumulone and hexahydroisohumulone in the beagle dog. Food Chem Toxicol. 1998;36:915-922.9771552

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This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.

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