Beer : Health and Nutrition

The liver and the digestive system
The Impact of Alcohol on Health 135
Heavy drinkers develop a poor and idiosyncratic appetite, which will focus on the ingestion
of fats and proteins rather than carbohydrates (Roe 1979). Alcohol in moderation,
however, stimulates the appetite (Hetherington et al. 2001).
Alcohol suppresses the ow of saliva (Enberg et al. 2001), making the meal tend to
be somewhat drier. Clearly beer would be expected to be better than wine in respect of
hydrating the bolus. Swelling of the salivary glands (parotids) is a symptom of a heavy
drinker (Santolaria et al. 1997).
Very heavy drinkers may also occasionally be prone to oesophagitis (Seifert 1995),
the re uxing of stomach hydrochloric acid into the oesophagus leading to ‘heart burn’
and ‘acid brash’.
Beer and to a lesser extent wine encourage the production of the hormone gastrin
that switches on the ow of the gastric juices in the stomach (Chari et al. 1993). The
stomach absorbs alcohol more ef ciently when it is full and it is metabolised more
quickly (Sedman et al. 1976). Less alcohol then passes to the duodenum, from which
alcohol is absorbed into the bloodstream very rapidly. Here is one explanation for the
reduced feelings of lightheadedness when a drink accompanies the eating of a full meal,
as opposed to nibbling.
Fasting appears to reduce the level of alcohol dehydrogenase (ADH; Riveros-Rosas
et al. 1997), a key enzyme involved in metabolising alcohol (Baraona et al. 1994), 90%
of which is metabolised by the liver. ADH produces acetaldehyde, which is toxic if not
adequately dealt with by the next enzymes in the cascade, aldehyde dehydrogenase.
An accumulation of acetaldehyde causes hangovers and liver damage in the long term
(Agarwal & Seitz 2001).
In men, 80% of ADH is in the liver and the remainder in the stomach (Myerson 1973).
Women produce less ADH, meaning that alcohol has more signi cant effects on them
(Seitz et al. 1993), although ADH levels in women increase after the menopause, so
that presumably older women are better able to deal with alcohol.
A secondary alcohol-metabolising system in the body, known as the microsomal
ethanol oxidising system (Lieber 1999), is probably stimulated to an increased extent by
regular consumption of alcohol. When oxidised through this system, alcohol provides
only two-thirds of calories that are generated when ADH deals it with.
The ADH system is polymorphic – and different in Asians (Li & Bosron 1986; Yoshida
et al. 1991). It is claimed that the genetic make-up of ADH impacts the response of
individuals to alcohol in respect of the levels of acetaldehyde produced (Yin & Agarwal
2001). Acetaldehyde may be the causative agent in several problems ascribed to excessive
alcohol consumption. The Chinese and Japanese ush very readily, due to a mutation
in one of the aldehyde dehydrogenases (Crabb et al. 1989).