What is the optimal level of drinking for living longer?
I find it very interesting that the usual reporting on alcohol use tends to report that 1 to 2 drinks per day is healthy, but going to 2 or 3 is severely harmful. Since it is very unlikely that any substance will have no doses between healthy and harmful, what does the research really say?
You are exactly right. While the optimal level for overall mortality in most U.S. studies is 1-2 drinks daily (although the range worldwide is up to five drinks daily, Poikolainen, 1995as in the famous Copenhagen study in which Grønbaek et al., 1994, found mortality gains for up to five drinks of wine daily), many studies have flat tails. That is, even while the study claims the optimal level is 1-2 drinks daily, there is no rise in mortality for those who drink more, at least for significant parts of the population. In this sense, the oft-described U- or J- shaped curve said to describe mortality by drinking is simply inaccurate.
To take one example, in a study in the New England Journal of Medicine which found mortality gains for drinking among older Americans, Thun et al. (1997) found no increase in mortality for high CAD-risk seniors up to five drinks/day. What is operating is that reduced risk of coronary artery disease is highly robust. Although other sources of death rise as drinks rise, in the Western world CAD is such an overwhelming source of mortality that it balances the rise in other causes. For high-CAD-risk populations, this conceivably could lead to recommendations of quite high optimal levels of alcohol consumption (up to five drinks daily).
On the other hand, women under age 50 with no CAD risk factors might actually be advised to drink at the very light end of the spectrum, particularly if they have a first degree relative with breast cancer. However, in the major study in this area, three-quarters of the women had at least one CAD-risk factor (Fuchs et al., 1995).
Fuchs, C. S., Stampfer, M. J., Colditz, G. A., Giovannucci, E. L., Manson, J. E., Kawachi, I., Hunter, D. J., Hankinson, S. E., Hennekens, C. H., Rosner, B., Speizer, F. E., & Willett, W. C. (1995). Alcohol consumption and mortality among women. New England Journal of Medicine, 332, 1245-1250.
Grønbaek, M., Deis A., Sørensen, T. I. A., Becker, U., Schnohr, P., & Jensen, G. (1995). Mortality associated with moderate intakes of wine, beer, or spirits. British Medical Journal, 310, 1165-1169.
Poikolainen, K. (1995). Alcohol and mortality: A review. Journal of Clinical Epidemiology, 48, 455-465.
Thun, M. J., Peto, R., Lopez, A. D., Monaco, J. H., Henley, S. J., Heath, C. W., & Doll, R. (1997). Alcohol consumption and mortality among middle-aged and elderly U.S. adults. New England Journal of Medicine, 337, 705-714.