Thursday May 12 2016
Don't overlook beer's high-calorie content
"Pint of beer a day could protect you from heart attacks," The Independent reports. A new review on the alleged protective effects of moderate beer drinking has been warmly welcomed by the UK media – but nobody reported that it was funded by an Italian beer trade association.
Researchers reviewed the existing evidence about beer and health, including the effects on heart and circulation, cancer, liver disease, dementia and overall length of life. They say that much research has been done on the effects of wine on health, but less on beer.
The research team claims that, based on the result of their review, men who drink the equivalent of around two 330ml cans of beer a day, and women who drink one can, will receive "some benefit against cardiovascular disease".
This recommendation equates to around 2.5 units of alcohol a day for men and 1.25 for women, or 17.5 units a week for men and 8.75 units for women.
For men, this advice contradicts recent advice issued by UK Chief Medical Officers that "you are safest not regularly drinking more than 14 units per week".
So, who's right? Well, the methods the researchers used to identify and select the evidence are not clearly reported.
This means it's possible that this review may not have considered all relevant research and, playing devil's advocate, could have ignored evidence countering the researchers' hypothesis.
What we do know is that there are safer, well-validated methods to reduce your risk of cardiovascular disease.
Where did the story come from?
The study was carried out by researchers from 10 research centres in Italy, Spain, Luxembourg and the US.
It was funded by the Italian Association of the Beer and Malt Industries, Assobira. The researchers say Assobira had no role in designing or writing the study.
Several of the researchers declared conflicts of interest in working for Assobira or other industry bodies linked to alcoholic drinks.
The study was published in the peer-reviewed journal Nutrition, Metabolism and Cardiovascular Diseases.
Disappointingly, not one single UK media outlet managed to report this arguably significant conflict of interest.
The study was met with enthusiasm by the UK media, although the quantities of alcohol recommended seemed to confuse some, and little mention was made of the downsides of this approach.
For example, The Daily Telegraph said, "drinking up to two 1.4 pints of beer a day for men and half of that for women" could benefit heart health.
However, the researchers define a healthy limit as "up to" one drink a day for women and two for men.
They say that one drink is approximately 330ml of 4% beer. That is equivalent to 0.58 of a pint – so the limit for men would be just over one pint, while the limit for women is just over half a pint.
What kind of research was this?
This was a consensus document, which means a group of experts were brought together to review evidence on the topic and agree a statement outlining their conclusions.
It is not clear from the document who chose the experts in the group, or whether they used standard systematic review methods to review published evidence.
The problem with non-systematic evidence reviews is that researchers might cherry-pick the research that suits them and ignore anything that doesn't fit their theory. We're not saying that happened in this case, but it's unclear how the studies were chosen.
What did the research involve?
A group of doctors were asked to review the evidence on the effect of the consumption of moderate amounts of beer on human health.
Each doctor carried out a search of the published literature before writing one section of the review, which was then shared for comments by other doctors. They arrived at a final version after meeting to discuss their findings.
While the study does tell us the search terms and the reasons for excluding studies from the review, it is unclear whether this was a formal systematic review.
The researchers did ask two external experts to review the manuscript as part of the process before meeting to prepare their final version.
They did not carry out a meta-analysis of their findings, but summarised the findings of the evidence they reviewed.
What were the basic results?
Low to moderate consumption of beer seems to have the same effect of reducing the chances of cardiovascular disease as wine.
This was the clearest finding from the review, based on a meta-analysis published in 2011 that pooled the results of 16 studies in almost 290,000 healthy adults.
The maximum protection against cardiovascular disease observed in that study – a 33% risk reduction – was seen at a consumption level of 25g of alcohol a day (about one pint of beer).
As with all alcohol, beer increases the risk of cancer, even at low levels. The paper says that "most alcohol-related cancers (85-90%) are in fact due to heavy drinking", which they define as more than two drinks a day.
However, light and moderate drinking were linked to increased risk of breast, mouth and throat cancers.
Importantly, the chances of alcohol causing cancer seem higher in Asian people. This is said to possibly be because there are genetic differences in many people of Asian origin that mean they are less able to process the toxins produced by alcohol.
There was insufficient evidence to show the effect of beer on the liver, apart from the known effects of consuming too much alcohol, which increases the chance of liver disease.
It is unclear whether beer increased or decreased the chances of getting dementia, as the studies reviewed gave conflicting results.
The effects of beer on length of life are also unclear, although the report's authors say they are likely to be in line with the known effects of drinking any alcohol.
These show a "J-shaped curve", with non-drinkers being slightly more likely to die than those who drink a small or moderate amount of alcohol, but those who drink a large amount of alcohol being more likely to die.
As the authors said, "Heavy alcohol (and beer) consumption increases the risk of total mortality, ranking eighth place among the causes of attributable deaths all over the world."
How did the researchers interpret the results?
The researchers said that, "Unless they are at high risk of alcohol-related cancers, there is no reason to discourage healthy adults who are already regular light-moderate beer consumers from continuing to follow the same pattern.
"On the other hand, we do not recommend that adult life-long abstainers begin drinking for health reasons as, up to now, there is no direct evidence that adult abstainers who start drinking beer or other alcoholic beverages (also in moderation) reduce their risk of chronic diseases."
In other words, if you don't drink beer, there's no reason to start – but if you're healthy and drink a small amount of beer, there's no need to stop.
Perhaps the most important message from this study is that low to moderate drinking may have health benefits, but binge drinking or heavy drinking is very bad for your health. The other message seems to be that beer has similar effects to wine.
Whether wine is good or bad for us has been debated for many years. Some have pointed to a reduction in the risk of cardiovascular disease, perhaps because of the phenols produced by fermented grapes, or perhaps because of alcohol itself. It seems that any benefits from wine are also seen in beer – as long as this is in moderation.
However, even drinking in moderation raises the risk of some cancers. Overall mortality figures suggest that the benefits may outweigh harms at low to moderate levels of drinking.
The researchers included 150 papers for their review, which suggests they carried out a careful study of the evidence.
However, without knowing if the review was carried out systematically, it's hard to know how rigorous the evidence-gathering process was. It is possible that some research relevant to the issue has not been considered.
A review's findings are only as strong as the underlying studies. The consistent themes identified suggest these are likely to be true effects associated with low to moderate beer consumption.
However, the underlying studies are only observational, so introduce the possibility of many sources of bias and confounding. For example, there could be inaccurate recall of the type of alcohol consumed or its quantity.
It is also possible that other health and lifestyle factors are influencing the results. Several of the studies adjusted their analyses for common ones such as age, smoking and body mass index, but otherwise there was considerable inconsistency in the factors that were taken into account.
The study's conclusions – that there's no need to stop drinking moderate amounts of beer if you're healthy and already do so, but no need to start if you don't drink already – seem sensible. It's worth reiterating that pregnant women and those with certain conditions are advised to avoid alcohol altogether.
Because of this review's lack of rigour, we would recommend that you ignore the advice that if you are a man, you can safely drink 17.5 units a week, and stick to the recent official UK guidance that both men and women should drink no than 14 units a week.
This is equivalent to a bottle-and-a-half of wine or five pints of export-type lager (5% abv) over the course of a week.
Read more about the new guidance and get tips on how to cut down on alcohol if you find yourself drinking too much on a regular basis.