Is there a 'safe' level of alcohol consumption?

By Cliff Harvey

In a recent article HPN's Emily White discussed the health benefits and risks of drinking wine. Since then there have been conflicting articles in the mainstream media around the topic of whether there is any safe level of alcohol intake. 

What Does the Evidence Tell Us?
We wanted to evaluate the in vivo, in situ evidence available from systematic reviews and meta-analyses and so a systematic search of these review types was conducted in MedLine and CINAHL yielded the following conclusions:

Systematic reviews of the evidence suggest that low level intake of alcohol (1-2 drinks per day) is associated with a reduced risk of Alzheimer’s Disease and dementia [2], diabetes [3, 4], reduced HbA1C [5],  reduced risk for Ischaemic Heart Disease (IHD) [6, 7] and multiple cardiac outcomes [8], improved cardiac markers [9], reduced risk for nasopharyngeal carcinoma [10], and a 10% reduction in total mortality risk [11], and is not associated with kidney function decline [12] nor weight gain [13]. 
Evidence for a protective effect of low to moderate drinking on stroke occurrence is lacking [14] although light alcohol use may be associated with reduced occurrence of ischaemic stroke [15]. 
A 2013 systematic review whilst finding unsurprisingly that moderate to heavy consumption of alcohol increases the risk of developing cancer of the oral cavity and pharynx, oesophagus, stomach, larynx, colorectum, central nervous system, pancreas, breast and prostate, did not find any association between alcohol consumption and an increased risk of cancers of the lung, bladder, endometrium and ovary. It was also observed that alcohol consumption may be inversely related to thyroid cancer [16]. 
Other reviews did not find any meaningful association between alcohol consumption and cancer of the ovary [17] or glioma [18].
However colorectal adenoma appears to be increased at all levels of alcohol consumption [19] and oesophageal and liver cancers appear to be increased with even moderate (approx. 2.5 drinks per day) alcohol use [20].

Is There a 'Safe' Dose?
The ‘nadir’ or dose at which total mortality is most positively influenced has been found to vary significantly between countries and may lie somewhere between less than 7 and 12 drinks per week for men and under 3 drinks per week for women [21]. 

Conclusion
It is clear that heavy drinking is detrimental socially, puts one at much greater risk of accident and violence and increases total mortality risk along with individual risk for nearly every condition that has been studied. 
Much of the current research suggests that any amount of ‘binge’ drinking is negative, and reverses any potential benefits from light alcohol use. 
There are also inherent risks for addiction and abuse arising from otherwise healthy use. 
The jury may always be out on this topic but it seems prudent that:

• If you don’t currently drink there is no good reason to start 
• If you do drink it is prudent to keep your intake down to under 7 drinks per week with no more than 2 drinks per day and ‘alcohol-free’ days each and every week. ​

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​References
1. Ronksley, P.E., et al., Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis. Vol. 342. 2011.
2. Ilomaki, J., et al., Alcohol Consumption, Dementia and Cognitive Decline: An Overview of Systematic Reviews. Current Clinical Pharmacology, 2015. 10(3): p. 204-212.
3. Knott, C., S. Bell, and A. Britton, Alcohol Consumption and the Risk of Type 2 Diabetes: A Systematic Review and Dose-Response Meta-analysis of More Than 1.9 Million Individuals From 38 Observational Studies. Diabetes Care, 2015. 38(9): p. 1804-1812.
4. Howard, A.A., J.H. Arnsten, and M.N. Gourevitch, Effect of alcohol consumption on diabetes mellitus: a systematic review. Annals of Internal Medicine, 2004. 140(3): p. 211.
5. Schrieks, I.C., et al., The effect of alcohol consumption on insulin sensitivity and glycemic status: a systematic review and meta-analysis of intervention studies. Diabetes Care, 2015. 38(4): p. 723-732.
6. Roerecke, M. and J. Rehm, The cardioprotective association of average alcohol consumption and ischaemic heart disease: a systematic review and meta-analysis. Addiction, 2012. 107(7): p. 1246-1260.
7. Roerecke, M. and J. Rehm, Alcohol consumption, drinking patterns, and ischemic heart disease: a narrative review of meta-analyses and a systematic review and meta-analysis of the impact of heavy drinking occasions on risk for moderate drinkers. BMC Medicine, 2014. 12: p. 182-182.
8. Ronksley, P.E., et al., Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis. BMJ (Clinical Research Ed.), 2011. 342: p. d671-d671.
9. Brien, S.E., et al., Effect of alcohol consumption on biological markers associated with risk of coronary heart disease: systematic review and meta-analysis of interventional studies. BMJ (Clinical Research Ed.), 2011. 342: p. d636-d636.
10. Chen, L., et al., Alcohol consumption and the risk of nasopharyngeal carcinoma: a systematic review. Nutrition & Cancer, 2009. 61(1): p. 1-15.
11. Jayasekara, H., et al., Alcohol Consumption Over Time and Risk of Death: A Systematic Review and Meta-Analysis. American Journal of Epidemiology, 2014. 179(9): p. 1049-1059.
12. Buja, A., et al., Is moderate alcohol consumption a risk factor for kidney function decline? A systematic review of observational studies. Journal of Renal Nutrition, 2014. 24(4): p. 224-235.
13. Sayon-Orea, C., M.A. Martinez-Gonzalez, and M. Bes-Rastrollo, Alcohol consumption and body weight: a systematic review. Nutrition Reviews, 2011. 69(8): p. 419-431.
14. Mazzaglia, G., et al., Exploring the relationship between alcohol consumption and non-fatal or fatal stroke: a systematic review. Addiction, 2001. 96(12): p. 1743-1756.
15. Patra, J., et al., Alcohol consumption and the risk of morbidity and mortality for different stroke types--a systematic review and meta-analysis. BMC Public Health, 2010. 10: p. 258-258.
16. de Menezes, R.F., A. Bergmann, and L.C.S. Thuler, Alcohol consumption and risk of cancer: a systematic literature review. Asian Pacific Journal Of Cancer Prevention: APJCP, 2013. 14(9): p. 4965-4972.
17. Huang, Y.-H., et al., Association between alcohol consumption and the risk of ovarian cancer: a meta-analysis of prospective observational studies. BMC Public Health, 2015. 15(1): p. 1-12.
18. Zhen-Yu, Q., et al., Alcohol Consumption and Risk of Glioma: A Meta-Analysis of 19 Observational Studies. Nutrients, 2014. 6(2): p. 504-516.
19. Zhu, J.Z., et al., Systematic review with meta-analysis: alcohol consumption and the risk of colorectal adenoma. Alimentary Pharmacology & Therapeutics, 2014. 40(4): p. 325-337.
20. Taylor, B., J. Rehm, and G. Gmel, Moderate alcohol consumption and the gastrointestinal tract. Digestive Diseases (Basel, Switzerland), 2005. 23(3-4): p. 170-176.
21. White, I.R., The level of alcohol consumption at which all-cause mortality is least. Journal Of Clinical Epidemiology, 1999. 52(10): p. 967-975.