Whether you would order a pint of lager or a bottle of Newcastle Brown Ale in the pub used to be a matter of taste. These days you might also choose to consider the antioxidant activity of your favourite beer. Cereal grains are a good source of antioxidants and not surprisingly beer, which is made from malted barley, also contains antioxidants. Beers with a high antioxidant score generally have a high content of polyphenols which have been shown to have useful antioxidant properties. A research group from UMDS, Guys Hospital, London, has measured the total antioxidant activity (TAA) of 21 beer samples (Walters M et al. BRFI Quarterly, April 1997:18-20). The lagers had a TAA in the range of 1.00-1.50 mM while the stouts and dark ales - due to a higher content of polyphenols - led the antioxidant contest with TAAs in the range of 1.50-2.00 mM.
Dr. Pilar Codoñer Frach, University of Valencia, has studied the polyphenol content of 80 different beers. Basically, the final content of phenolic components of a beer depends on both the raw materials (malted barley and hops) and the brewing process. Dr. Frachs results confirmed previous reports of a higher polyphenol content of dark beers. "Bitter" style beers showed the highest levels of phenolic components. However, when moving from in vitro (test tubes) to in vivo (liver cell cultures) investigations Pilar Frach found no difference in antioxidant activity between light beer and dark beer samples. In conclusion her results show that beer is a product with an important antioxidant capacity - and you may feel free to choose between lager, ale and stout entirely according to your own taste.
Hop constituents - the spice in beer
Hops - an essential and unique ingredient of beer - contribute to the characteristic aroma and bitterness that makes beer the thirst quenching drink enjoyed by the consumer. Hops also act as a natural antibiotic, ensuring that the beer remains fresh to drink. Many hop constituents, however, also add health properties to beer, according to the research of Prof. Denis de Keukeleire, director of Pharmacognosy and Phytochemistry at Ghent University, Belgium. He has carried out research on hops and beer for 35 years.
2-4 grams of hops are needed for every litre of beer leading to ca. 100 mgs per litre hop-derived constituents which account for various medicinal properties:
- Sedative compounds with stress combating and sleep inducing properties.
- Flavonoids with potent antioxidant activity protecting against reactive oxygen species.
- Compounds with bacteriostatic, fungistatic and antiinflammatory action.
- Estrogenic compounds counteracting complaints related to the menopause.
- Bitter compunds which stimulates the digestive tract.
- Compounds with diuretic activity and beneficial effect against bladder complaints.
Most prominent among the bioactive hop constituents are the prenylated flavonoids that are transferred to a significant extent (up to 4 milligrams per litre) from hops to beer. According to research in progress at Ghent University prenylated hop flavonoids have an effect on enzymes that affect the ratio of androgenic and estrogenic hormones in prostate cells with an inhibition of BPH (benign prostatic hyperplasia) as a possible result. The interesting finding from the test tubes of Ghent University is in accordance with recent results from the Health Professionals Follow-up Study: moderate alcohol consumption almost halved the American Health Professionals risk of BPH (Am J Epidemiol 1999;149:106-15).
Among the 20 compounds, which have been identified to date, 8-prenylnaringenin (hopein) appears to be the most intriguing compound with possible chemopreventive power:
- Inhibition of cytochrome P450 enzymes which mediate metabolic conversion of procarcinogens to carcinogens.
- Inhibition of human aromatase and 5a -reductase = a possible inhibition of prostate cancer.
- Inhibition of angiogenesis (formation of new blood vessels) = a possible inhibition of metastasis (spread of cancer from one organ to another part of the body).
Working with a screening program for chemo-preventive action of natural compounds Dr. Norbert Frank, senior scientist in the division of Toxicology and Cancer Risk Factors at Deutsches Krebsforschungszentrum in Heidelberg, found xanthohumol (XN) from hops to be a very promising agent. Laboratory experiments have shown that XN is protective at all levels of the carcinogenic process. Going from laboratory to animal experiments Dr. Frank could demonstrate that XN at very low concentrations prevented the early stages of carcinogenesis in cultured mouse mammary glands providing a first direct proof for its chemopreventive potential.