There's so much conflicting evidence on alcohol and health, it's enough to make your head spin.
In the last few months alone, German researchers reported that even just one drink a day can boost the risk of breast cancer (Alcohol Alcohol, 2012 Mar 29; Epub ahead of print), while American investigators found that "light-to-moderate" drinking can slash the risk of stroke (Stroke, 2012; 43: 939-45).
Other studies suggest that alcohol can both help and hinder sleep (Alcohol Clin Exp Res, 2011; 35: 2093-100), and strengthen and weaken bones (Am J Clin Nutr, 2009; 89: 1188-96).
So how do we make sense of the science, and should we ditch or indulge in that daily drink?
The cancer connection
We often hear that a glass of wine a day can do us good but, in the context of cancer, not drinking at all may be the better option for preventing the disease.
According to a report by the World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR)-the largest-ever inquiry into lifestyle and cancer-drinking just small amounts of alcohol can significantly increase the risk of certain cancers, such as those of the mouth, throat, vocal cords, oesophagus, breast and bowel. This increased risk was seen for all kinds of alcohol-beers, wines, spirits and others-suggesting that the crucial factor is the ethanol content, not the other ingredients in the drink. In fact, ethanol, pure alcohol, is classified by the International Agency for Cancer Research (IACR) as a cancer-causing agent in humans.
Although not all the evidence agrees-for example, research on kidney cancer suggests that alcohol might actually have a protective effect-the conclusion of the WCRF-AICR report is stark: "From the point of view of cancer prevention, the best level of alcohol consumption is zero."
But rather than recommending that we all avoid alcohol alto-gether, the authors' advice is to "limit consumption to no more than two drinks a day for men and one drink a day for women". One 'drink' contains about 10-15 g of ethanol, they explain. This seemingly contradictory advice is because, while alcohol appears to increase our chances of getting cancer, it may also slash our risk of heart disease (WCRF- AICR. Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, 2007; www.dietandcancerreport.org).
Helping the heart
Numerous studies have found that people with low-to-moderate alcohol intakes have a reduced risk of heart disease. In one 'meta-analyses'-a pooled analysis of the results of several studies-researchers in Canada and the US found that alcohol drinkers compared with non-drinkers had significantly lower risks of heart disease and stroke, and death from either condition. No more than one alcoholic drink a day was consistently associated with a 14- to 25-per-cent reduction in the risk of all heart-related outcomes assessed, they found. But drinking more than that was associated with an increased risk of fatal stroke (BMJ, 2011; 342: d671).
The same researchers went on to investigate the possible mechanisms behind alcohol's apparent heart-healthy effects. They looked at more than 60 studies on alcohol consumption in relation to known markers for heart disease, and found that moderate amounts of alcohol significantly increased levels of 'good' HDL cholesterol circulating in the body. This could explain the protective effect of alcohol against heart disease (BMJ, 2011; 342: d636).
Interestingly, when also looking at the impact of the type of alcohol consumed (wine, beer and spirits), it was found that all had similar heart-healthy effects. However, most of the studies assessed had used wine-and usually red wine-as the alcohol intervention, which may have biased the results. (Red wine contains plant compounds called 'polyphenols' like resveratrol, thought to be good for the heart.)
Nonetheless, most of these red wine studies concluded that it was the alcohol in the drink that was responsible for the healthy effects rather than any other component. One study compared the effects of drinking red and white wines with two different types of grape juice (one high and one low in polyphenols) on levels of cholesterol in the blood. Both the red and white wines increased HDL cholesterol levels, whereas the grape juices had virtually no effect (Clin Chim Acta, 1996; 246: 183-93).
So, it appears that alcohol itself-in moderation-can have favourable effects on the body that can bring about long-term benefits for the heart.
Binge drinkers beware
If you want to reap the benefits of alcohol, however, avoid binge drinking at all costs. Says Dr Juergen Rehm, director of social and epidemiological research at the Centre for Addiction and Mental Health (CAMH) in Toronto, Ontario, "If someone binge drinks even once a month, any health benefits from light to moderate drinking disappear." Binge drinking is defined as more than four drinks on one occasion for women, and more than five for men.
Dr Rehm's own research into alcohol and the heart-a meta-analysis of 44 studies with co-author Michael Roerecke-has revealed that, while drinking does appear to protect against heart-related disease and death in general, a protective effect cannot be assumed for all drinkers, not even at low levels of alcohol intake. Their paper, published in the journal Addiction, suggests that drinking patterns may be just as important as how much alcohol is drunk overall (Addiction, 2012 Jan 9; doi: 10.1111/j.1360-0443.2012.03780.x).
A study comparing the drinking patterns of middle-aged men in France (Lille, Strasbourg and Toulouse) and in Northern Ireland (Belfast) supports this. It found that, although the French typically drank more than the Irish on a weekly basis due to drinking every day rather than drinking more on fewer occasions, the French drinkers had considerably less coronary heart disease than did the Northern Irish imbibers. Binge drinkers, who were more likely to be from Belfast, had nearly twice the risk of a heart attack or death from heart disease compared with regular, daily drinkers (BMJ, 2010; 341: c6077).
Some experts, however, warn against daily drinking even in moderation. UK MPs, for example, have recently called for "two alcohol-free days each week" to be added to the Department of Health guidelines on drinking. The current advice is that men should not regularly drink more than 3-4 units of alcohol a day while women should not regularly drink more than 2-3 units (one unit is equal to around 8 g of ethanol; visit the NHS website for more details), which they believe might encourage drinking every day, which may not be healthy.
Indeed, Sir Ian Gilmore, the Royal College of Physicians' special advisor on alcohol, points out that there is an increased risk of liver disease in those who drink every day, or nearly, compared with those who drink only periodically or intermittently. Dr Nick Sheron, a liver expert at the University of Southampton, agrees: "If we look at who gets scarring of the liver-cirrhosis-they're pretty much all drinking on a daily basis."
Dr Sheron also emphasizes that weekly 'dry' days are important for maintaining a healthy relationship with alcohol. "Alcohol shares the inherent property of nearly every drug," he explains. "If you drink on a regular basis, you will develop a tolerance. You need more alcohol to have the same effect. Having a rest from it can help to reset your tolerance levels." In other words, daily drinking could lead you to drink more than is good for you. It could also lead to a dependence on drink, which is never healthy.
The bottom line
Ultimately, when it comes to deciding whether alcohol is good or bad for you, it's complicated. While it can cut your risk of heart disease, it can also raise your risk of cancer, and there's a fine line between healthy and risky amounts.
Yet, looking at death rates, it appears that moderate drinkers tend to live longer than abstainers, even after taking factors such as education and wealth into account (J Am Geriatr Soc, 2009; 57: 955-62). So, it looks as if a bit of what you fancy may do you good-provided that you limit your daily amount and take a couple of days off each week to give your liver a chance to recover.
Although experts differ over what constitutes a 'safe' daily dose, given the latest findings, it may be sensible to limit your daily intake to 15 g of ethanol if you're a woman (say, a standard glass
of wine or a pint of lower-strength beer) or 30 g if you're a man (roughly a large glass of wine or a pint of higher-strength beer). But if you don't drink at all, it's not worth starting, as you're likely to get the same benefits from a healthy diet and regular exercise.
Factfile: Alcohol: good or bad?
- Dementia. Light-to-moderate drinking has been linked to a reduced risk of dementia and mental decline, whereas abstainers, heavy drinkers and binge drinkers appear to have an increased risk (J Alzheimers Dis, 2010; 22: 939-48).
- Diabetes. Drinking in moderation compared with not drinking appears to reduce the risk of type 2 diabetes by about 30 per cent (Diabetes Care, 2005; 28: 719-25).
- Obesity. One 13-year study found that, compared with non-drinkers, normal-weight women who drank one or two drinks a day gained less weight over the course of the study and were less likely to become overweight or obese (Arch Intern Med, 2010; 170: 453-61).
- Lung cancer. Findings from the California Men's Health Study suggest that drinking a glass of red wine a day can cut the risk of cancer among smokers and ex-smokers by 60 per cent. However, no clear association with lung cancer was seen for white wine, beer or spirits (Cancer Epidemiol Biomarkers Prev, 2008; 17: 2692-9).
- Better bones. Drinking red wine may protect against bone loss in older men, while drinking low-alcohol beer may be protective for women (Eur J Clin Nutr, 2011; 65: 526-32).
- Pancreatitis. Drinking just one measure of spirits increases the risk of acute pancreatitis-inflammation of the pancreas causing stomach pain and vomiting for a few days. But drinking wine or beer does not appear to have the same effect (Br J Surg, 2011; 98: 1609-16).
- Sleep problems. Having a drink can help you to fall asleep, but may interfere with sleep quality and the restorative role of sleep, according to studies in Japan (Alcohol Clin Exp Res, 2011; 35: 2093-100).
- Birth risks. Drinking more than one drink a day (about 10 g of ethanol) while pregnant can increase the risk of low birth weight, preterm birth and other complications compared with not drinking at all (BJOG, 2011; 118: 1411-21).
- Bone problems. Heavy drinking is bad for bones and can lead to osteoporosis (Osteoporos Int, 2012; 23: 1-16). Consuming too much alcohol appears to interfere with the genes responsible for maintaining healthy bone growth and development (Alcohol Clin Exp Res, 2008; 32: 1167-80).