Thursday May 20 2010
Wine does not appear to directly improve heart health
“Drinking up to three glasses of wine a day could make you healthier,” claimed the Daily Mirror.
The news is based on French research, which found that the health of moderate drinkers was better than that of non-drinkers and heavy drinkers according to certain measures, including body mass index, blood pressure and levels of depression. However, the researchers crucially stress that alcohol intake was not found to cause these improvements, but rather that people who drank moderately also had better overall health and social status.
While many past studies have found that moderate alcohol intake is associated with a lower cardiovascular risk, this new research provides a valuable exploration of this much-debated association. Despite many persistent theories, there is little solid proof that moderate drinking can directly improve heart health. There is also a wealth of evidence to show that alcohol negatively affects other aspects of health.
Where did the story come from?
The study was carried out by researchers from Hopital de la Pitie and the IPC (Investigations Preventives et Cliniques) Center in Paris, France. It was funded by French public health bodies, the Caisse Nationale d’Assurance Maladie (CNAM) and the Caisse Primaire d’Assurance Maladie de Paris (CPAM-Paris). It was published in the peer-reviewed European Journal of Clinical Nutrition.
This research was generally covered well by the media, with most stories making it clear that alcohol had not been found to improve health, but rather that people who drank moderately also had better health and social status. The messages from some headlines were more misleading, however, with Metro claiming that “Drinking wine makes you happier” and The Sun suggesting that booze “aids the body”.
The Daily Mail featured particularly clear coverage, with both its headline and article clearly explaining that the good health of moderate drinkers is more likely to be down to healthier diet, exercise and work–life balance rather than any supposed benefits of alcohol.
What kind of research was this?
This cross-sectional study analysed the relationship between alcohol intake, other cardiovascular risk factors and health status in a large French population. The aim was to evaluate potential confounding factors that may be behind the supposed cardiovascular benefits of alcohol.
The researchers looked at data on the clinical and biological characteristics of nearly 150,000 people, which were gathered as part of a large ongoing cohort study.
Several observational studies have shown an association between moderate alcohol intake and a lower risk of cardiovascular disease. The lower risk is often attributed to alcohol having beneficial effects on blood levels of lipids, such as cholesterol, or on other factors, such as the effect of the antioxidants in alcoholic drinks. The researchers point out that addressing the underlying message implied by previous data, that moderate alcohol intake is good for health, is particularly important in France, which has one of the highest average individual alcohol intakes in the world.
The researchers also stress that the findings from observational studies need to be viewed with caution, so they assessed a number of key factors not taken into account by previous research. These key, but generally unexplored, factors included mental wellbeing, subjective health status and social factors.
What did the research involve?
All the people in the study underwent a clinical examination between 1999 and 2005, which included measurements of blood pressure, waist circumference, cholesterol, respiratory function and heart rate. Also recorded were tobacco use, physical activity, personal medical history, current medications, social status and occupation. Stress and depression scores were assessed using validated questionnaires, and people were also asked to estimate their own health status.
Alcohol intake was quantified as the number of standardised glasses of pure alcohol (10g a glass) consumed each day, and different types of alcoholic drink were also recorded. People were divided into four groups according to their alcohol consumption: never, low (less than 1 glass a day), moderate (1-3 glasses a day) or high (more than 3 glasses a day). Former drinkers were analysed as a separate group. Established statistical techniques were used to analyse the relationship between alcohol intake and all the other factors. The results were adjusted to account for the influence of age and were also broken down by gender.
What were the basic results?
The researchers found that:
- 13.7% of men and 23.9% of women did not drink at all.
- Total alcohol intake increased with age in both sexes.
- Apart from people aged under 30, most people drank wine.
They found that women who drank moderate amounts of alcohol had lower body mass index, waist circumference, blood pressure and blood lipids, including LDL (“bad”) cholesterol. Men who drank moderately had lower body mass index, heart rate, blood pressure, some blood lipids (triglycerides) and fasting glucose levels, plus lower stress and depression scores.
Men who drank little or moderately were also more likely to have better self-assessed health status, social status and respiratory function. In both sexes, alcohol intake was strongly associated with higher levels of HDL (“good”) cholesterol, a finding which was independent of the type of alcoholic beverage consumed.
How did the researchers interpret the results?
The researchers concluded that moderate and low consumption of alcohol was strongly associated with several clinical, social and biological characteristics that point to overall better health status and a lower risk of cardiovascular disease. Importantly, according to the researchers, few of these factors seem causally related to alcohol consumption.
They point out that social status was “strikingly different” across the groups, with moderate alcohol consumption being a “powerful general indicator” of social status. Risk factors that have never been taken into account before, such as social and professional status, anxiety score and heart rate, were all more favourable in moderate consumers.
Their results, they say, raise the possibility that the seemingly protective effects of moderate alcohol consumption found in previous research may have been due to the researchers not fully taking account of possible confounders.
This research adds a note of caution to the results of previous studies. It concludes that moderate alcohol consumption may be a marker of better health and lower cardiovascular risk rather than a cause of these improvements.
The study’s strength is that it is based on a relatively large cohort and that standardised, validated methods were used to collect clinical and biological information. The main weakness of the study is its cross-sectional design, which means that people were not followed up over time to see if they developed disease. This also meant that deaths from heart disease, for example, were not reported.
Another limitation is that alcohol intake was based on self-reported data. This leaves a possibility for error as accurate recall of alcohol consumption is notoriously hard in this type of study. Future research in this area will ideally follow people over time and carefully measure possible risk factors to establish whether alcohol has any direct, causal role in protection from heart disease.
Overall, this study has implications for public health. As the researchers say, its results suggest that it is premature to promote alcohol consumption as an independent factor for cardiovascular protection, as some people have proposed based on past research.