Low-risk drinking guidelines: the scientific evidence

In 1997 the Addiction Research Foundation of Ontario and Canadian Centre on Substance Abuse released updated guidelines for low-risk alcohol consumption. This paper presents the scientific rationale behind this statement. Important comprehensive overviews on the consequences of alcohol use were studied. Formal meta-analyses on morbidity and mortality were examined wherever possible. Individual elements from similar guidelines were investigated for their scientific foundation. Limited original analyses defined risk levels by average weekly consumption. The evidence reviewed demonstrated that placing limits on both daily intake and cumulative intake over the typical week is justifiable for the prevention of important causes of morbidity and mortality. Gender-specific limits on weekly consumption were also indicated. In these updated guidelines intended for primary prevention, days of abstinence are not necessarily recommended. Intoxication should be avoided and abstinence is sometimes advisable. Available evidence does not strongly favour one alcoholic beverage over another for cardiovascular health benefits.

Endothelial cell fibrinolysis: transcriptional regulation of fibrinolytic protein gene expression (t-PA, u-PA, and PAI-1) by low alcohol

Epidemiological studies have associated moderate alcohol consumption with a reduced risk for coronary artery disease (CAD) and myocardial infarction (MI). This cardioprotection may be attributed to alcohol-induced changes in a variety of cellular functions, including increased fibrinolysis. Fibrinolysis is important in regulating normal hemostasis. Endothelial cells (ECs) synthesize fibrinolytic proteins, t-PA, u-PA, and PAs inhibitor, PAI-1. Systemic factors, i.e., alcohol, that affect one or more of these components, resulting in increased EC fibrinolysis, will reduce the risk for thrombosis, CAD, and MI and afford cardioprotection. These studies will identify/define the effects of low ethanol (< 0.1%, v/v) on the expression of PAs, PAI-1, and surface-localized fibrinolytic activity in cultured ECs. Low ethanol exerted a short-term time- and dose-dependent increase (approximately 5- to 8-fold) in activity at approximately 20 min and 0.05% ethanol, which was sustained for approximately 1 hr. On the other hand, a single brief exposure to low ethanol (< 0.1%, < 120 min), followed by 4-24 hr incubation in the absence of ethanol, showed a time- and dose-dependent increase (approximately 2- to 3-fold) in PAs antigen/mRNA and a concomitant approximately 2- to 3-fold sustained increase (approximately 24 hr) in fibrinolytic activity. Further nuclear transcription run-on assays and transient transfection experiments, using pPAs/luc and pPAI-1/luc promoter constructs, demonstrated that low ethanol transcriptionally upregulates t-PA and u-PA gene expression and downregulates PAI-1 gene expression. These combined studies have described a feasible molecular mechanism by which low ethanol can induce and sustain increased surface-localized EC fibrinolysis that may underlie and contribute, in part, to the cardioprotective benefit associated with moderate alcohol consumption.

The J-shaped curve and changes in drinking habit

The accepted interpretation of the J-shaped curve relating alcohol intake to mortality or coronary heart disease is that the lowest point on the curve (light/moderate drinking) represents optimum exposure to alcohol and that the increased risk in non-drinkers reflects the consequence of sub-optimum exposure. However, non-drinkers, both ex-drinkers and lifelong teetotallers, consistently show an increased prevalence of conditions likely to increase morbidity and mortality compared with occasional or light drinkers. In addition, regular light drinkers tend to have characteristics extremely advantageous to health. Changes take place in alcohol intake in individuals over time, with a strong downward drift from heavy or moderate drinking towards non-drinking, affected to a considerable extent by the accumulation of ill health. Reduction in alcohol intake or giving up drinking is associated with higher rates of new diagnoses than remaining stable in alcohol intake and also with higher rates of both cardiovascular and non-cardiovascular mortality. The use of non-drinkers as a baseline, and failure or inability to adequately take into account the characteristics of subjects in the different alcohol intake categories, exaggerates the risk of coronary heart disease events and all cause mortality in non-drinkers and the benefits of light/moderate alcohol intake.