Therapeutic hop oil

Hops are at present used almost exclusively as a basic ingredient for the brewing of beer, since hop acids and essential hop oil are crucial for the taste and smell of beer. However, the hop has been extensively used throughout history as a health-promoting medicine. Hops have always occupied a prominent place in pharmacopoeia and scientific reference works. The hop is described as a sedative used to treat agitation, fear and nervous sleep disturbances. This concerns, by preference, hop cones containing at least 0.35% essential oils. In Germany there are more than 50 products and preparations that contain hops for these indications on the market. Dried hop cones(‘strobuli’) in powder form are used as a starting material for these medicines. The pharmacological nomenclature knows them as ‘Strobuli lupuli’.

In the past the hop was reputed to have yet other therapeutic properties. The plant was used to treat hypersensitivity, nervous anxiety, depression, cramps, neuralgia, migraine and even obesity. Hops were also supposed to produce antiseptic, antibiotic, analgesic, moisture repellant, tuberculostatic and anaphrodisiac effects. The use of hops in modern medicine is limited to the sedative effect of the hop cones. Although the mechanism of this effect remains unexplained, various studies have shown that hops do in fact have a mildly tranquillizing effect and induce sleep. Hops and essential hop oil are so complex that the effect probably cannot be ascribed to one single component, but rather to an interaction between different components. Hop extracts examined in the laboratory do not necessarily react in the same way as in a natural environment. One more reason why the health-giving effects of hops are so difficult to investigate in traditional clinical studies as we know them.

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In pharmacological practice, hops are usually combined with other sedative plant extracts such as valerian, passion fruit or balm. That makes it even more difficult to gain an idea of the effects of the hop taken separately. It is supposed that the sleep-inducing effect must be ascribed to the essential hop oil. In this train of thought, a cushion filled with hops is commonly reputed to be an efficient aid for sleep. The cushion must however be regularly filled with fresh hops. Heat (body temperature, the heat of the face) causes the essential oil to vaporize and produce a soothing effect (a sort of aromatherapy).

Calming herbal teas with a basis of hop are also available. Hop tea is not for boiling in water. It is better prepared as an infusion with hot water in a closed teapot. Hops are used not only to make tea, but also in the form of pills, dragees, extracts, syrups and tinctures (phytotherapy). Another interesting application is bath oil or gel with hop extracts, which are held to have calming, stress-relieving properties.

An immediate response to hop preparations is certainly not the rules. In general, a course of treatment should be taken for a specific period to obtain any effect. In prestigious health resorts, such as Bad Gögging in Germany, use is often made of the relaxing effect and other medicinal properties of the hop.

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Hop polyphenols as phyto-oestrogens and anti-carcinogenics

Very little attention has hitherto been devoted to the other proven bio-active properties of hops. The Laboratory for Pharmacognosis and Phytochemistry of the Faculty of Pharmaceutical Science a the University of Ghent, led by Prof. Dr. D. De Keukeleire, has therefore set up a research programme on the oestrogen and cancer-protective properties of the hop. It has long been known that excessive exposure to hop influences the female hormonal cycle, and that menstrual disturbances used to occur more frequently among women hop-pickers. This effect was ascribed to a specific polyphenol in the hop, namely xanthohumol. Without further proof, however.

Specific polyphenols, such as genistein and daidzein, were recently detected in a number of beers, admittedly in extremely low concentrations (up to 30 nanomol per litre). These polyphenols, also present in soya, are phyto-oestrogens (substances of vegetable origin that imitate the activity of the natural female hormone, oestradiol). Phyto-oestrogens are supposed to offer protection against specific hormone-sensitive cancers (breast cancer, prostate cancer).

The oestrogen effects of different hop varieties were scientifically researched in the Ghent laboratory by means of two independent in-vitro tests. The results confirm that hops do, in fact, have a slight oestrogen activity. The different hop varieties examined displayed significant differences in oestrogen effect. The Ghent researchers concluded that hops are one of the richest natural sources of phyto-oestrogens, comparable with soya beans.

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The oestrogen activity is not caused by xanthohumol, as originally supposed. Nor do the traces of genistein and daidzein appear to be responsible. The Ghent research group discovered that hop - as far as they knew – contained the most powerful phyto-oestrogen in nature: 8-prenylnaringenine. The oestrogen effects of that phyto-oestrogen have since been confirmed via in-vivo studies.

The presence of 8-prenylnaringenine in hops at once offers an explanation for the menstrual troubles among hop-pickers. Since hops are now harvested by machine, this phenomenon has disappeared and long-term exposure to such high concentrations of hop-polyphenols is a thing of the past.

The only way in which humans have to content with 8-prenylnaringenine and other phyto-oestrogens in hops is by the consumption of beer. The oestrogen activity of beer is dependent on the choice of hop variety and on conditions during the brewing process. This means that there are oestrogen and non-oestrogen beers. Because phyto-oestrogens have undeniably positive effects on health, efforts have been made to use hop varieties displaying a particular oestrogen effect. But even the most high-oestrogen beers probably have only little effect on human health. The concentrations of phyto-oestrogens in beer are low, and nothing is yet known regarding its availability in the body as a consequence of beer consumption. What has been discovered is that the hop, an important ingredient in beer, has some very promising health-promoting and medicinal properties that merit further investigation.

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