Beer : Health and Nutrition

140 Chapter Six
Juhl et al. (2001) produce evidence to refute the claim that there is any link between
alcohol consumption and waiting time to pregnancy (i.e. fecundity).
Lapcik et al. (1998) and Gavaler (1998) demonstrated that beer contains a range of
health-promoting iso avonoids (phytoestrogens) (see also Walker 2000). There have
been concerns that such materials may adversely modify the hormonal status of men,
but Promberger et al. (2001) have concluded that the risk is negligible owing to the
extremely low levels of these substances found in beer. Equally, of course, this does
bring into question whether such low levels have any bene cial effects either. The
level of the principal iso avonoid found in beer (isoxanthohumol, 1.5 mg/L or less) is
about 20-fold lower than the effective human dose for anti-cancer treatments (Forster
& Koberlein 1998). More on this later.
The xanthohumol found in hops is devoid of oestrogenic activity but 8-prenylnaringenin
is not (De Keukeleire et al. 1997a). It seems that this is the most potent oestrogen
yet identi ed. Hops are more effective than the widely used plant preparations to relieve
postmenopausal symptoms (Dixon-Shanies & Shaikh 1999). Hop extracts suppress
menopausal hot ushes (Goetz 1990).
Hops are now being included in some herbal preparations for women for breast
enhancement. Milligan et al. (2000) investigated the relative oestrogenic, androgenic
and progestogenic activities of 8-prenylnaringenin in comparison to 6-prenylnaringenin,
6,8-diprenylnaringenin and 8-geranylnaringenin. While the latter three exhibited some
oestrogenicity, their potency was less than 1% of that of 8-prenylnaringenin, which
alone competed strongly with 17 β-estradiol for binding to both the α- and β-oestrogen
receptors. None of the compounds tested, which also included xanthohumol,
isoxanthohumol, 3′-geranylchalconaringenin, 6-geranylnaringenin and 4′-O-methyl-
3′-prenylchalconaringenin, as well as polyphenolics from hops, showed progestogenic
or androgenic bioactivity. This indicates that the endocrine properties of hops and hop
products are due to the very high oestrogenic activity of 8-prenylnaringenin.
It has been estimated (Milligan et al. 1999) that beer might account for some 10% of
the daily intake of phytoestrogens (vegetables, cereal grains and especially soya beans
are rich sources too). The phytoestrogens are said to counter breast and prostate cancer,
as well as cardiovascular disease (Knight & Eden 1996).
Emanuele and Emanuele (1998) present an alarming review of the impact of excessive
alcohol consumption on male potency. There is interference with the function
of each of the three main components of the male reproductive system, namely the
hypothalamus, the anterior pituitary gland and the testes. The impact is impotence,
infertility and reduced secondary sexual characteristics. Alcohol can adversely affect
the Leydig cells of the testis that produce and secrete testosterone. Alcohol also impairs
the function of the Sertoli cells that play an important role in sperm maturation in the
testis. Alcohol can decrease the production, release and activity of luteinising hormone