Alcohol consumption in the new millennium – weighing up the risks and benefits for our health

• 1 Introduction
• 2 An introduction to alcohol and alcoholic beverages
  • 2.1 How is alcohol produced
  • 2.2 The production of alcoholic beverages
  • 2.3 Calculation of alcohol content in beverages
  • 2.4 Other measures of alcohol
• 3 Guidelines for sensible drinking
  • 3.1 UK guidelines
  • 3.2 Guidelines for sensible drinking around the world
• 4 Alcohol consumption
  • 4.1 Current alcohol intakes in the UK
  • 4.2 Recent trends in alcohol intake in the UK
  • 4.3 Trends around the world
• 5 Absorption and metabolism of alcohol
  • 5.1 Absorption of alcohol
  • 5.2 Alcohol metabolism
• 6 Alcohol and nutrition
  • 6.1 Nutrient composition of alcoholic beverages
  • 6.2 The effect of alcohol on energy intake
  • 6.3 Nutritional implications of chronic excessive alcohol consumption
  • 6.4 Other components of alcoholic beverages
• 7 The burden of disease and mortality related to alcohol
• 8 Alcohol and disease risk
  • 8.1 Methodological problems of studies assessing associations between alcohol consumption and disease risk
  • 8.2 Alcohol and bodyweight
  • 8.3 Alcohol and coronary heart disease
  • 8.4 Alcohol and blood pressure
  • 8.5 Alcohol and stroke
  • 8.6 Alcohol and type 2 diabetes
  • 8.7 Alcohol and cancer
• 9 Alcohol and other conditions
  • 9.1 Adverse reactions to alcohol for some susceptible individuals
  • 9.2 Alcohol and peptic ulcers
  • 9.3 Alcohol during pregnancy
  • 9.4 Alcohol, bone mineral density and fracture risk
  • 9.5 Alcohol and renal dysfunction
• 10 Alcohol and social issues
  • 10.1 Short‐term psychological and psychomotor effects of alcohol intake
  • 10.2 Crime and public disorder as a result of drinking alcohol
  • 10.3 Alcohol‐related harms and other public health issues
  • 10.4 The economics of alcohol consumption
  • 10.5 Population‐based initiatives underway to reduce the incidence of binge drinking
• 11 Conclusions

Summary Alcohol is produced via the anaerobic fermentation of sugars by yeast and involves glucose molecules (C₆H₁₂O₆) being broken down to yield ethanol (C₂H₅OH), carbon dioxide (CO₂) and energy. The amount of alcohol contained in different alcoholic beverages varies considerably and is referred to as the ‘strength’ of the drink, which is expressed as the percentage of alcohol by volume (ABV). A standard unit of alcohol in the UK equates to 8 g or 10 ml of pure alcohol. Guidelines for sensible drinking set by the UK government are 3–4 units (24–32 g) a day or less for men, and 2–3 units (16–24 g) a day or less for women. Specific recommendations have been set for those planning pregnancy and pregnant women, who should drink no more than 1–2 units of alcohol once or twice a week and should avoid heavy drinking sessions. Guidelines for sensible drinking are similar in other countries. When taking into account the standard drink unit used to define guidelines, the most commonly recommended limit is 24 g/day for men and 20 g/day for women. Older people are more likely to drink in line with the sensible drinking guidelines, as they tend to consume alcohol over a period of time, as opposed to consuming large quantities on one or two days of the week, a practice that is more popular among younger people. Consuming double the sensible drinking guidelines in one day is classified as binge drinking (an alternative definition is drinking until intoxicated). It has become recognised that binge drinking is a common phenomenon in the UK, particularly among younger people. Other factors, such as income, ethnicity and region of residence, are also recognised to be predictive of the quantity of alcohol consumed; for example, higher‐income households are more likely to consume large quantities of alcohol and consume alcohol more frequently. The quantity of alcohol consumed is an important factor in determining how it affects health and well‐being. In terms of nutritional health, chronic excessive alcohol intake is well recognised to affect an individual’s nutrient status, because it reduces food intake and/or may interfere with the digestion, absorption, metabolism and utilisation of some nutrients. However, when consumed in moderation, alcohol is unlikely to interfere with the metabolism of nutrients or be associated with impaired vitamin function or depletion to an extent that may harm health, provided that dietary intakes are adequate. Alcoholic beverages contain alcohol, carbohydrate and only small amounts of some vitamins, trace elements and minerals. They are therefore unlikely to contribute significantly to micronutrient intake. Any association that exists between moderate alcohol consumption and the absorption and metabolism of nutrients from the diet is dependant on a number of factors, including: the nutrient in question; habitual intake of the nutrient and the nutritional status of the individual; and the quantity of alcohol consumed over a period of time. Overall, little information exists about the implications of binge drinking on nutrient status; but it may alter food intake, and excessive alcohol consumption can cause disturbances to the digestive system. While infrequent binge drinking is unlikely to have any long‐term nutritional implications (although it may affect nutrient status in the short‐term), regular binge drinking may have a more negative impact. Although alcoholic beverages tend to have few nutrients, they can be a significant source of energy, as alcohol provides 7 kcal per gram. Studies indicate that alcoholic beverages are usually additive to an individual’s normal energy intake and individuals are unlikely to compensate for energy from them during the day. The aperitif effect of alcohol may also encourage an increase in energy intake. It is therefore not surprising that alcohol intake has been associated with weight gain and an increase in body mass index (BMI) (with the exception of chronic excessive drinkers). However, there are a number of methodological problems that need to be considered when comparing the findings of studies investigating the association between alcohol intake and disease risk, including: potential misreporting of total intake; the use of an appropriate control group; and the need for comparable measurement units. Consumption of alcoholic beverages has also been associated with increasing the risk of ill‐health associated with pre‐existing conditions. For example, it may contribute to ulcer development or aggravate symptoms of existing ulcers. There is evidence that moderate alcohol consumption during pregnancy may affect the development of the fetus’s central nervous system, and may result in low birthweight. However, there is currently no consensus as to whether alcohol should be completely avoided during pregnancy. However, it is well recognised that excess alcohol consumption during pregnancy can put the fetus at risk of fetal alcohol syndrome. Quantity of alcohol consumed is particularly important when considering the association between alcohol and chronic diseases; for example, there is now strong evidence that light to moderate (1–3 drinks per day) consumption decreases the risk of a coronary heart disease (CHD) episode compared with abstainers (with particular benefits in men aged over 55 years and post‐menopausal women). However, heavy drinking is associated with an increased risk of CHD. Further information is required to determine the association between drinking patterns and heart health. However, there is a consensus of opinion that it is the alcohol per se that influences heart health, rather than a particular type of alcoholic beverage; and other factors that affect an individual’s choice of drink may be important in distorting the findings from studies that show otherwise. As with risk of CHD, light to moderate alcohol consumption is associated with a decreased risk (of 30–40%) of type 2 diabetes, when compared with teetotallers. Heavy drinking may be associated with an increased risk, resulting in a ‘J’ or ‘U’ shaped relationship between alcohol consumption and the incidence of type 2 diabetes. A ‘J’ shaped relationship has also been reported between alcohol consumption and blood pressure. It is widely accepted that heavy alcohol intake is a risk factor for high blood pressure, and evidence indicates that moderate intakes may exert a short‐term lowering effect, while abstainers/teetotallers are reported to have a higher blood pressure. The type of stroke is important when considering the association between stroke and alcohol, as any alcohol consumption is associated with an increased risk of haemorrhagic stroke, but low intakes (i.e. one drink per day) may have a protective effect on ischaemic stroke. Heavy drinking is associated with an increased risk of both types of stroke. Alcohol intake has also been associated with an increased risk of cancers at a number of sites. However, a consensus for a likely causal association has only been identified between alcohol and cancers of the upper‐aero digestive tract and liver. The mechanisms to explain the positive associations between alcohol and breast cancer, and alcohol and colorectal cancer, have yet to be identified. It is unclear whether some types of alcoholic beverage are more strongly associated with increased risk of cancer than others. Mechanisms identified to date suggest that it is the alcohol per se that exerts damage and, therefore, quantity of alcohol consumed is the most important variable. Studies looking at the relationship between alcohol and mortality suggest that 10–80 g (approximately 1–8 drinks) of alcohol each week is optimal to reap the health benefits, but increased risk is noted at higher intakes (thus indicating a ‘U’ shaped relationship between alcohol intake and mortality). Gender and age are important factors when considering the association between alcohol and mortality. For example, for younger people, the benefits of alcohol may be outweighed by the increased risk of other diseases (e.g. alcohol‐related cancers, liver cirrhosis) and increased risk of violence and accidents. Aggressive behaviour, increased risk taking and decreased responsiveness to social expectations, which may lead to personal ‘harm’, including accidents and violence, are usually the result of alcohol intoxication (i.e. through binge drinking). Excess alcohol consumption may also result in a ‘hangover’, which disrupts normal life through symptoms of fatigue and increased anxiety, and has economic consequences in the workplace through poor performance or absenteeism. The extent to which a hangover can affect an individual’s performance, including psychomotor, recognition and managerial skills, is still being debated. Binge drinking is also associated with an increased risk of sexually transmitted diseases and unplanned pregnancies. Although the cost of binge drinking in terms of long‐term health has yet to be established, the significant economic cost is well recognised. A number of population‐based initiatives are underway to try and change the ‘drinking culture’, and thus reduce the incidence of binge drinking. Initiatives include: advertising campaigns; changes to alcohol advertising regulations; and changes to pub licensing regulations.