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Is drinking in moderation good for my heart?

Thursday, February 18, 2010

We all know prolonged heavy drinking and regular bouts of binge drinking are bad for our health. But what about light or moderate drinking? Is a small amount of alcohol actually good for the heart? Mythbusters investigates…

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Claims there were possible benefits for the heart from drinking moderate amounts of alcohol first emerged in the 1970s. Since then, a huge amount of research has focused on alcohol’s potential cardio-protective effect.

There are several plausible biological mechanisms for this idea – alcohol increases the profile of ‘good’ fats such as HDL cholesterol and has an anti-clotting effect on blood – but alcohol also has many other effects that are harmful to cardiovascular health, including raising blood pressure and promoting electrical rhythm disturbances.

Despite the popular notion that a little alcohol is good for the heart, the research is far from clear. For years, a J-shaped curve was used to describe this effect – teetotallers were thought to fare worse than moderate drinkers who in turn fared better than heavier drinkers. This view is now under serious challenge. Several early studies that looked at the association between alcohol and heart disease have been faulted for their design and methods.

Non-randomised trials may have overestimated the apparent benefits of light to moderate alcohol consumption on the risk of coronary heart disease because they were influenced by uncontrolled confounders. For example, people who only consume light to moderate amounts of alcohol also tend to have healthier lifestyles than heavy drinkers, while many abstainers do so because they already have health problems, not so they can avoid them.

Another source of error is the systematic misclassification of exdrinkers and occasional drinkers as abstainers, which negatively biases the health status of abstainers.

Most studies also failed to capture drinking patterns that may be more relevant to disease causation than overall consumption. As a result of these shortcomings, many researchers now believe that the size of alcohol’s cardioprotective effect has been exaggerated.

When it comes to the link between alcohol and cancer, there is little ambiguity. Any level of alcohol is harmful, and there is no level of consumption below which there is not an increased risk of cancer. For breast cancer, each additional standard drink per day increases the risk by 9 percent. The risk of mouth, pharynx and larynx cancer increases by 25 percent per standard drink per day.

Not surprisingly, the World Health Organization has classified alcohol as a Class 1 carcinogen, alongside asbestos and formaldehyde. Yet public understanding of the risks of moderate alcohol intake is low. In a recent US survey, almost one-third of all drinkers cited health benefits as part of their motivation for drinking. Just 10 percent correctly identified breast cancer as a possible risk from moderate drinking.

The underlying dynamics behind much of the research into the potential health benefits of alcohol reflect the powerful commercial interests at play as much as they reflect improvements in our knowledge about the biological effects of alcohol. A recent review of major studies investigating the alleged protective nature of alcohol on the heart made a startling discovery. Studies reporting a positive protective effect had all been funded by the liquor industry whereas those that showed a negative or no effect had not received any industry funding. This does not mean that industry-funded research is deliberately biased, but it should encourage a more cautious approach when interpreting and reporting results.

Coronary heart disease affects 35 percent of men and 28 percent of women in New Zealand during their lifetime. The idea that alcohol might somehow prevent this may sound attractive but is not substantiated by the evidence.

The overall harms from alcohol overwhelmingly outweigh any potential cardiovascular benefit for most people. Worldwide, at least 2.3 million people died of alcohol-related causes in 2002, and in New Zealand, alcohol is associated with an estimated net loss of 12,000 years of life annually.

While there are many valid reasons to drink alcohol – sociability and relaxation to name just two – Mythbusters thinks improving cardiovascular health should no longer be among them.

References

Chikritzhs T, et al. A health dose of skepticism: Four good reasons to think again about protective effects of alcohol on coronary heart disease. Drug Alcohol Review. 2009 Jul;28(4):441-4.

Connor J, et al. The burden of death, disease and disability due to alcohol in New Zealand.  NZ Medical Journal 2005 April 15;118(1213):U1412.

Mukamal KJ, et al. Beliefs, motivations and opinions about moderate drinking: a cross-sectional survey. Family Medicine 2008;40(3):188-95.

Mukamal KJ, Rimm EB. Alcohol consumption: risks and benefits. Current Atherosclerosis Report. 2008 December ;10(6):536-43.

Sellman D, et al. Alcohol cardio-protection has been talked up. NZ Medical Journal 2009 Sepember 25;122 (1303).