Alcohol's (other) Dark Side

The sixth report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI) describes “excessive” alcohol intake as a risk factor for hypertension. Reduction in intake to 1 oz of ethanol per day (≤2 “drinks”) is one of the lifestyle modifications recommended in hypertension management;1 however, regular alcohol intake has not received much attention in regard to hypertension, as it is dwarfed by the well-publicized issues of weight, sodium intake, and exercise in blood pressure control. Furthermore, the finding that moderate alcohol intake may be cardioprotective rationalizes its use, and possible abuse, by patients. Substantial evidence supports a hypertensive effect of alcohol, with increases in blood pressure that are proportional to intake.2 Prospective studies that reduced alcohol intake corroborate these findings.3 A threshold level is difficult to define precisely, but it appears that around three drinks per day is the point at which blood pressure elevation becomes significant. This translates roughly into three 12-oz cans of beer, three 6-oz glasses of wine, or three mixed drinks. The threshold level is lower in smaller patients and women. The average increase in blood pressure from alcohol is in the range of 5/3 (systolic/diastolic) mm Hg, just shy of about one half of the usual blood pressure reduction from most antihypertensive agents. Studies evaluating the mechanisms for the alcohol-induced elevations in blood pressure suggest several causes. A major factor appears to be a central nervous system mediated increase in sympathetic nerve activity.4 An under-appreciated aspect of alcohol intake and blood pressure control is the resistance to drug therapy that patients with increased alcohol intake may manifest. This is not unlike the reduced antihypertensive drug response with excessive sodium intake. Experience in this regard is largely anecdotal, though, to some extent, it is born out in the literature. Studies of heavy drinkers (five to six drinks per day) with hypertension suggest that abstinence will significantly lower the percentage who remain hypertensive5 and that there is a high incidence of heavy drinkers in hypertensives who are drug resistant.6 What is the importance of these findings to the average practitioner? We suggest two answers. First, the failure to respond as expected to antihypertensive therapy usually triggers an investigation of causes of drug resistance, and alcohol intake, as a cause, should be on the list of suspects. Second, despite the evidence showing that modest amounts of alcohol (up to two drinks per day) are cardioprotective, the blood pressure increasing effects of intake above this level likely trump any cardioprotective benefits. Perhaps the best advice is that of the Stoics: All things in moderation. In this case “moderation” is two a day or less.