A pint a day

Beer is one of the most ancient foods known to humankind. Grain was being fermented to brew beer as long ago as ca 3500 BC – 2000 years before it was used in baking bread. Used as payment, ration, or gift, beer has been drunk and celebrated by people all over the world for thousands of years. Up to 300 years ago it was safer to drink beer than surface water because the water used in brewing had been boiled, and until recently stout was frequently prescribed for post-natal women and the infirm.

Beer is a complete food: it contains water, carbohydrates, protein and micronutrients (Table 1). The modest levels of alcohol in beer improve blood circulation, reducing the risk of heart disease for light drinkers compared with that for heavy drinkers and abstainers.

The main component of beer is water, which makes up ca 93% of the beverage by weight. Ignoring any water derived from metabolism, a healthy 70kg adult human needs 2.1 l of water per day, equivalent to about 4 pints.

Compared with other alcoholic drinks, beer is better able to quench thirst because it contains less alcohol per volume and its high water content more than compensates for its dehydrating effects. Moreover, since many beers are isotonic (ie they have the same osmotic pressure as body fluids), they have negligible impact on the water balance of the body.

Carbohydrates derived from malted barley also feature prominently in beer, which generally contains about 15g per pint. Less than 2g of this is fermentable sugar, the rest being dextrins (intermediate products obtained during the transformation of starch into maltose and d-glucose). Carbohydrates are a major source of energy; a pint of beer provides about 180kcal (cf 240kcal for cola and 200kcal for skimmed milk), though unlike other sugary foods such as jams and soft drinks it does not promote tooth decay.

Interestingly, ethanol has a calorific value of 7.1kcal per gram – almost twice that for carbohydrates, which supply about 4.1kcal per gram. In addition, beer includes a small quantity of dietary fibre – non-starch polysaccharides such as cellulose and pectin – compounds that make up plant cell walls. Stouts include just 1g of dietary fibre per pint, while lighter beers contain less than half of even that amount.

Table 1

	Beer	Milk (whole)	Orange juice (unsweetened)	Sports drink
Calories / kcal	180	369.2	187.4	386.2
Water	528	497	503.8	464.0
Carbohydrate	15	26.7 (all lactose)	48.28 (all sugars)	102.24 (50% sugars)
Protein	2	18.7	2.3	–
Alcohol	17.5	–	–	–
Fat	–	21.6	–	–
Metals (mg):
Na	61.2	284	22.7	164.7
K	246.1	852	738.4	5.7
(Na:K ratio)	1:4	1:3	1:32	29:1
Ca	44.2	68.2	51.1	28.4
Mg	44.2	68.2	51.1	5.7
P	80.8	540	85.2	22.7
Fe	<0.1	<3	2.84	<1
Cu	<0.3	<0.2	<1	<0.3
Zn	–	<2	<2	–

Contrary to popular opinion, however, beer does not contain any fat. Rather, the pot bellies of heavy drinkers probably result from the effects of alcohol as an appetite stimulant. This is partly countered by the carbon dioxide content of beer, which encourages drinkers to imbibe the drink in small amounts with pauses, allowing time to satisfy their thirst. Carbonated drinks also promote stomach acid formation (helping digestion) and stimulate blood flow to the muscles, brain, lungs and kidneys. Nevertheless, those on a calorie-controlled diet still need to reduce their beer consumption because the body preferentially burns the carbohydrates derived from beer rather than body fat.

One other fact about beer that may come as a surprise is its fairly high content of protein and vitamins. Beer contains about 2g of protein per pint, one-seventh of which occurs in the form of the constituent amino acids. Amino acids perform many important metabolic roles; for example they are involved in activating enzymes, controlling the body’s pH and converting energy for use in muscles. Malt is the main source of t hese amino acids, and beers brewed exclusively from malt, rather than those brewed using malt and adjuncts, are richest in protein. 

Perhaps even more surprisingly, beer also contains nearly 4g per pint of water-soluble B vitamins: rich in niacin, pantothenic acid, pyridoxine and riboflavin, beer is relatively low in only two B vitamins, thiamin and biotin. Beer also includes significant amounts (26µg per pint) of folic acid – a vitamin taken by pregnant women to reduce the incidence of foetal spinal abnormality. One of the other benefits of drinking beer is that unlike some other drinks, it contains relatively low levels of sodium. Typically, the Na:K ratio is just 1:4, compared with a ratio of 29:1 for some sports drinks. 

The level of dietary calcium in beer is also generally low – only about half as much as in white wine – while the nitrate content of beer (ca 5µg per pint) is well below the maximum level set by the World Health Organisation. 

In addition, potentially toxic metals, such as cadmium, chromium, cobalt, lead, mercury and tin, are virtually absent. This is partly because breweries often use spring water, which is relatively free of chemical additives, and which will have absorbed very little metal from old pipework. Another reason is that during fermentation the sulphur groups in the yeast act as a sponge for most of the heavier metals, removing them from solution. Yeast cells are extremely sensitive to their environment and are readily poisoned by metals that are toxic to humans. Yeast is therefore a useful yardstick for the nutritional wholesomeness of a beer: if yeast has thrived to produce the beer, it is safe to drink. 

Another metal that is found in relatively low concentrations in beer is aluminium. Aluminium is the most abundant metal in the Earth’s crust and it is present in almost all foods. A survey by the Ministry of Agriculture, Fisheries and Food (Maff) found that beers contain between 5 and 6500ppb of aluminium, with a median value around 100 ppb (ca 57µg per pint). This is the same aluminium content as for canned cola, and 36 times less than occurs in tea.

Although background concentrations of aluminium are non-toxic to humans, some years ago a number of scientists endeavoured to prove a causal link between aluminium in the diet and Alzheimer’s disease. Today the Alzheimer’s debate is focused more upon vascular causes,16 but the supposed threat from aluminium remains in the public perception. One perceived threat was thought to result from the storage of acidic beer in aluminium cans and kegs; in fact a protective lacquer prevents aluminium containers from being dissolved into the beer. 

Because humans have evolved in an environment in which aluminium is ubiquitous, it is not surprising that the metal is not generally bioavailable from the gut. Of the aluminium in our diet, 95% remains in the alimentary canal until faecal excretion, and of the little that does get into the bloodstream, most is excreted via the kidneys.

Besides its low metal content, another advantage of beer as a beverage is its antiseptic and sterile properties. In the 12th century, German monks added hops to their ale for medicinal purposes, while in the 14th century, hops were added to Flemish ale to create bitter-tasting ’biere’ – a drink that could survive transport and storage without spoilage. 

To this day beer travels better than milk or water as regards bacteriological contamination. Compounds called iso-a-acids, derived from hops in the copper boil, have antibacterial properties and even the alcohol itself is an antiseptic. Moreover, the process of boiling the wort (the liquid extracted from the grains during mashing) before fermentation ensures that microbes are absent. Even on the rare occasions when the few species of bacteria that can survive in beer are present, they generally only compromise the taste and appearance of the beer rather than pose any serious risk to human health. 

Interestingly, recent research links the presence of iso-a-acids to preventing osteoporosis in the elderly; apparently the iso-a-acids block so-called osteoclast pE2 receptors, thus inhibiting old bone resorption. 

As far as we know, drinking moderate amounts of beer has no adverse effects on human health; the UK brewing industry is controlled and regulated by more legislation than the sum of the controls over the pharmaceutical and radiochemical industries. 

Indeed, research now reliably suggests that drinking moderate amounts of beer may even be beneficial for human health. Work published in the 1970s first suggested a causal link between modest alcohol intake (an average of one pint of beer per day) and a reduced incidence of heart disease. People who drank a small amount of beer or wine seemed to be at a lower risk from heart attacks than those who abstained completely. These findings were remarkable, but critics explained the data as ’skewed’ because the sample population of abstainers included former heavy drinkers who had given up drinking due to heart disease or other health complications. 

More recent studies have corrected for the potential skewing of data from the abstaining population and have still found those who drink an average of 14 units of alcohol per week (equivalent to seven pints of beer) are at less risk from heart disease than those who drink heavily or not at all. In 1991, for example, a report in The Lancet noted that drinking alcohol increased the amount of various fractions of high density lipoproteins (HDL) in the bloodstream, ’associated with a reduced risk of coronary artery disease’. Further, the study showed that relatively high levels of HDL cholesterol and low levels of low density lipoprotein (LDL) cholesterol in the blood associated with moderate alcohol intake reduced the risk of heart attacks. 

Fibrous and stringy in nature, LDL cholesterol clings to the walls of arteries to form web-like structures that cause blockages to develop (atherosclerosis). HDL cholesterol, which is hard-packed and pellet-like, batters these LDL cholesterol webs as it travels through the arteries, knocking the LDLs free, and therefore scouring the arteries clean. Another well known benefit of moderate alcohol consumption is its link to a reduced incidence of gallstones. These normally form when bile becomes supersaturated with cholesterol. Research suggests that alcohol can decrease the amount of cholesterol the body produces, reducing the tendency for gallstones to form. 

The liver of a 70kg human can process 7g of alcohol per hour (about half a pint), up to a maximum of 150g over 24 hours. The occasional heavy drinking bout causes no lasting damage (provided that driving, machinery and traffic are avoided). Persistent heavy drinking, however, results in heart disease, cirrhosis of the liver, obesity, impaired control and response times, behavioural changes and problems in family or social life. 

But although alcohol is chastised for its addictive properties and harmful effects on health when taken in excess, smoking poses far greater health risks. UK Home Office statistics for 1990 show that smoking was responsible for nearly four times as many deaths as alcohol in the UK (110,000 as opposed to 30,000). 

It is way past time then to dispel some of the myths about beer. When used as part of a balanced diet, beer is beneficial for human health, and the infrequent mishap resulting from a little over-indulgence is no reason to brand beer as contrary to our well-being. With Yuletide fast approaching those of us who enjoy the occasional pint ought to take heart from these statistics. Time for another perhaps? 

Acknowledgements

David R. Williams is professor of speciation and analytical chemistry and Jeremy C. Philpott is a postdoctoral researcher in the department of chemistry, University of Wales.

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