Latest scientific news 01 October 2019

The J-curve – an ongoing debate: a scientific fact or justified doubts?

Scientists have recently entered the scientific debate to discuss previous and current criticisms of the J-shaped curve between wine/alcohol consumption and lower total mortality risk.

Almost a century ago, a study found that moderate drinkers of alcoholic beverages seem to live longer than those who abstain and those who drink heavily. Since then, many studies have shown such a J-shaped relationship between wine/alcohol consumption and the risk to die from any kind of disease (all-cause mortality risk).

The lowest risk is found with a consumption of 10 g of alcohol per day which translates in a 15% lower risk compared to abstainers. In this relationship, it is important to consider the drinking pattern: the most favourable pattern for health is to drink regularly but moderately with the meals and avoid binge or heavy drinking.

Lately, some studies have doubted/dismissed the existence of such J-curve and suggested that zero alcohol intake is the best option for health.

The researchers of this paper discuss the most common criticism such as confounding factors like the sick quitter theory as well as the concern that moderate drinkers have lifestyle characteristics that could explain their longevity compared to abstainers. The authors explain that these limitations have been addressed in dozens of well-controlled studies and confirm that the J-curve remained.

The challenge with such studies is that unmeasured confounding and bias can never be completely excluded. These are important issues in research, but they should be equally applied to all studies. Data on alcohol-related harm derive from the same studies as data on benefits yet concerns about bias and confounders are rarely raised when harms are discussed.

Nonetheless, since cause and effect cannot be established in observational studies, the researchers conclude that it is important to critically review scientific data and challenge them over and over again. However, some findings may be more reliable than others because they have relevant and biological explanations (such as beneficial changes in the HDL cholesterol, lower blood clotting, etc. which contribute to the lower mortality risk among moderate drinkers).

Finally, it is often suggested that the increasing involvement of industry in scientific research may affect the objectivity of independent scientists and the integrity of science. Taken all together, these elements result in conflicting messages in the media and different national alcohol guidelines, creating confusion and disbelief in science among the public.

Because of the limitations of observational studies, the authors suggest that more definitive and solid answers to the controversies around the health benefits of moderate wine/alcohol consumption could be provided by large, controlled and long-term intervention trials.

Costanzo S. et al, Moderate alcohol consumption and lower mortality risk: Justified doubts or established facts?, Nutr, Metabolism & Cardiovascular Diseases 2019, 29(10:1003-1008.

For more information about this article, read the scientific abstract here.

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