Anxiety measures using the “State-Trait Anxiety Inventory” (STAI).
The effects of hops on sleep modulation were confirmed in both experimental animal models and human clinical trials. A recent review is given by Zanoli & Zavatti . But to what extent do the levels of the hops present in normal beer have a sedative effect on the organism?
In normal beer the concentration of hops is about 0.3% . Therefore a moderate intake of beer of two 1/3-litre portions per day (666 ml), an amount recommended by several medical scientific societies , , , would contribute about 2 g of hops per day, or 25.7 mg/kg in an average weight human.
In the 1970s, Bravo et al.,  showed that there was a significant decrease in motor activity in mice after intraperitoneal administration of hop extract, although at rather high doses. Subsequently, its analgesic effect and decrease in spontaneous motor activity were confirmed also in a mouse model, with there being an enhancement in the induction of sleep by pentobarbital .
The sedative property of hops has been confirmed in humans, being greater when acting in combination with valerian (Valeriana officinalis), with the two acting synergistically on sedative function , , , , , . Schellenberg et al.,  studied the combined effects of hops and valerian on central nervous adenosine mechanism, observing an increase in alpha waves while assessing EEG data, with sleep inducers being generated through the adenosine receptors. To this action on adenosine, one must also add the hypnotic effect on the CNS through receptors for serotonin  and the hormone melatonin , , , which are involved in sleep and circadian rhythms, respectively.
Our study in a population of health professionals experienceing a considerable amount of work stress showed that, even though there was no increase in the length of repose in bed, there was a clear improvement in the quality of night-time sleep after the ingestion of beer at the end of the day. This is illustrated by the reduction in sleep latency and the notable reduction in nocturnal mobility, thereby achieving restful sleep which was reflected in decreased anxiety .
We would note that a greater hop content of the beer, but without increasing the alcohol content, could be expected to have led to a greater sedative action, both earlier and faster, in our population, but always at moderate doses since otherwise there could arise unwanted effects. The reason for this opinion is that other work, applying substantially higher Humulus lupulus concentrations (800 mg/kg=160 mg dose), and in association with anæsthetics and hypnotics such as ketamine, led to prolonged states of deep narcosis . Similarly, the product of the oxidative degradation of the α-acid content of fresh hops, 2-methyl-3-buten-2-ol, applied to mice at concentrations of 0.8 g/kg produced narcosis that lasted 8 hours . In other study by Zanoli et al. , oral administration of hop extracts to mice achieved a reduction in spontaneous locomotor activity. In particular, extract concentrations of 10 and 20 mg/kg b.w. were used, and increased sleep time and reduced motility compared to control animals were observed.
In a biphasic animal model, the common quail (with, like humans, a nocturnal period of sleep and diurnal activity), we have studied the effect of hop extract concentrations similar to those in beer, observing a decrease in motor activity during the night .
The results thus suggest that, because of its hop content, beer may have a possible use as a sedative in humans. The mechanism would principally be by modulating the GABAergic response through the effects of the hop components myrcenol , xanthohumol, and such α-acid derivates  as 2-methyl-3-buten-2-ol.
As with other food components, beer should always be only moderately consumed. Its use in this way and at supper-time could and should represent a nutritional tool in the discipline of chrononutrition, since its neuromodulatory components help entrain the circadian sleep/wake rhythms . Thus future lines of research will be to examine the possibility of achieving a higher level of sedation and reducing anxiety with the ingestion at supper-time of alcohol-free or low alcohol content beer with a higher hop content than we tested in the present work.
Through its hop content, alcohol-free beer could exert a sedative action in humans, apart from its benefits for health when consumed in moderation , among which are its anti-cancerigenous and cardiovascular health , ,  properties. One can therefore conclude that a moderate consumption of non-alcoholic beer will favour night-time rest, due in particular to its hop components, in addition to its other confirmed benefits for the organism.
Competing Interests: The authors have declared that no competing interests exist.
Funding: The authors gratefully acknowledge financial support for this study through the Plan I.D.T.I de la UEx, 2010 Acción VII, Proyectos de Iniciación a la Investigación y el Desarrollo Tecnológico; the Consejería de Sanidad y Dependencia, Junta de Extremadura; the Vicerrectorado de Investigación, Innovación e Infraestructura Científica, Universidad de Extremadura; and the Centro de Información Cerveza y Salud (CICS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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