Beer : Health and Nutrition

152 Chapter Six
cancer cells, indicating that it may inhibit metastasis (Rong et al. 2001). And so hop
extracts in very low concentration are very ef cient inhibitors of breast cancer cells
(Zava et al. 1998).
8-Prenylnaringenin is claimed to counter enzymes involved in the development of
prostate cancer and to inhibit the formation of new blood vessels important in tumour
growth (De Keukeleire et al. 2001). Small wonder that this molecule has been renamed
hopein, from hop and hope. Tagashira et al. (1995) showed that the hop alpha and beta
acids have potent ability to suppress lipid peroxidation.
Kondo and Arimoto reported to the Pharmaceutical Society of Japan and the US
National Cancer Institute (see Japan Today www.japantoday.com, 10 May 2002 – Kondo
& Arimoto 2002) that they gave beer to rats that had been injected with carcinogens
and showed that there was a 50% lowered incidence of cancer as compared to control
animals not receiving the beer. The authors suggest that this level of beer intake equates
to 250–500 mL for a 60-kg man. It was suggested that the active ingredients are pseudouridine
and betaine.
Humulone can inhibit growth of skin tumours in mice (Yasukawa et al. 1995) and it
can inhibit the growth of leukaemia cells (Honma et al. 1998). The polyphenol quercetin
can inhibit synthesis of DNA of human leukaemia cells (Uddin & Choudhry 1995), block
synthesis of a protein that leads to development of colon cancer in humans (Hosokawa
et al. 1990), inhibit propagation of stomach cancer cells in humans (Yoshida et al. 1990)
and inhibit growth of squamous cell carcinoma of throat and head in rats (Castillo et
al. 1989). Quercetin may suppress growth of breast cancer cells (Stangl 2001). The
phenolic acids can inhibit formation of carcinogenic nitrosamines from nitrite and
secondary amines while xanthohumol and isoxanthohumol (as well as beer per se) can
inhibit the mutagenic effect of heterocyclic amines (Arimoto-Kobayashi et al. 1999;
Miranda 2000b). Incidentally, humulone inhibits ear oedema in mice (Yasukawa et al.
1993). Pignatelli et al. (1983) showed that beers with the highest content of polyphenol
were the ones most able to block nitrosation events in the rat. Yoshikawa et al. (2002)
demonstrated the presence of pseudouridine in a diversity of beers and demonstrated
its ability to counter mutagens.
So how are we to reconcile the con icting observations? I believe it is essential to
recognise that there is a substantial variance between studies based on the dosing of
isolated materials, perhaps in atypically high concentrations, whether it be alcohol or a
purported protectant, and those investigations that are closer to the ‘real world’ in which
the various materials are together in better balanced quantities, e.g. in the form of beer.
The reader must appreciate that beer (and, indeed, wine) is not unique as a source of
antioxidants. The essential point that I wish to convey is that beer is comprised of the selfsame
type of molecules that are found in other foodstuffs. It is a responsible attitude to
regulate the intake of these materials so as to obtain a well-balanced diet (see Chapter 4).
Where beer (and other alcoholic beverages) offers a relatively unique proposition is for