Beer : Health and Nutrition

The Composition of Beer in Relation to Nutrition and Health 109
reactions with other components of the product (Thompson et al. 1990). Furthermore,
ethanol inhibits the absorption of thiamine by the body (Hoyumpa 1980).
Thiamine de ciency stimulates alcohol consumption (Pekkanen 1979): thiamine
shortages interfere with glucose metabolism, so perhaps the same causal inverse link
referred to earlier between intake of alcohol and carbohydrate is at play. The body does
not need thiamine to deal with ethanol and there are better substrates than fats, so thiamine
de ciency may be expected to promote the tendency toward alcohol consumption
(Segovia-Riquelme et al. 1971; Yki-Jarvinen 1988).
Levels of ribo avin increase through malting and brewing, whereas nicotinic acid
levels increase in malting and decline during brewing.
Mayer et al. (2001) have demonstrated the worth of beer as a source of folic acid,
leading to a decreased homocysteine content in blood (hyperhomocysteinemia is a signi
cant risk factor for vascular diseases – see Chapter 6). Chronic alcoholism leads to
the obverse effect, although beer drinkers had signi cantly lower serum concentrations
of homocysteine than did those consuming wine or spirits (Cravo et al. 1996). Cereals
are rich in folate and so it is no surprise that beer is a richer source of this material than
are other alcoholic beverages (Savage et al. 1995).
Walker et al. (2001b) report folate levels of between 47 and 125 µg/L in a range of
lagers, ales and a weissbier, which displayed the highest concentration. The extractable
level of folate increased during germination of barley, which the authors ascribe
to its synthesis in the embryo, though it may be a result of increased availability for
extraction. Typically about 4 mg/kg folate is present in ale and lager malts, with less
in barley and other adjuncts, so beers produced from a malt-rich grist might give
more folate.
Substantial loss of folate occurs during mashing and this is thought to be due to
oxidation and heat inactivation. Losses, though, are low in wort boiling and wort
clari cation. There is no net effect of fermentation on folate – yeast makes folate to
balance that which is lost presumably through adsorption effects. There is some loss
of folate (up to 50%) in the nal package due to ill-de ned changes occurring during
packaging and storage.
Vitamin C is found in barley and green malt, but is destroyed on kilning (Harden &
Zilva 1918). Some brewers add it to beer as an antioxidant.
Minerals
The mineral content of beer is illustrated in Table 5.9, while that of beer in relation
to other foods is shown in Table 5.10. Beer is rich in magnesium and potassium, but