Most of my counseling to patients about lowering blood pressure through self management is heavy on weight loss and light on dietary causes of high blood pressure – other than the obvious ones that make people gain weight.
Denial of the effects of dietary salt on blood pressure is not the issue. Rather, it is a time-hewn lack of confidence in the ability of patients to significantly and consistently modify their diet. Part of this may also relate to our inability to provide useful lifestyle tips on how to do so, other than the obvious referral to a dietitian. Telling them not to eat out does not solve this problem, because they can just as easily add salt at home.
However, a recent meta-analysis evaluating the effect of salt substitutes on blood pressure has reinvigorated my desire to counsel my patients on blood pressure self-management.
In this study, the investigators sought randomized, controlled trials with interventions lasting at least 6 months in duration ( Am. J. Clin. Nutr. 2014;100:1448-54 ). Six cohorts were identified in the literature involving a total of 1,974 participants. Included studies took place in China and the Netherlands. Three studies used 65% NaCl/25% KCl/10% MgSO2, one used 41% NaCl/41% KCl/17% magnesium salt/trace minerals, and one used 65% NaCl/30% KCl/5% calcium salt and folic acid.
Salt substitutes had significant effects on systolic blood pressure with a mean difference of –4.9 mm Hg and on diastolic blood pressure with a mean difference of –1.5 mm Hg.
Overall, one may not be impressed with a 5–mm Hg change in systolic blood pressure. But this is the mean difference – and we presume population heterogeneity in response to salt substitution, such that some patients will respond to a higher degree than this and some to a lower degree. But we do not know which ones are which.
Population interventions aimed at reducing salt intake have been shown to be effective. The Finnish government, for example, collaborated with private industry and was able to achieve reductions in sodium content of food. That initiative resulted in a 33% reduction in the population’s average salt intake, a greater than 10–mm Hg decrease in the population average of both systolic BP and diastolic BP, and a 75%-80% decrease in both stroke and coronary artery disease mortality. Australia, Japan, and the United Kingdom were able to do similar things.
Because we are unlikely to ever see such organized political will exercised in the United States, it seems reasonable to recommend salt substitutes to our patients on an individual level. Adverse effects have been noted with salt substitutes in patients with kidney disease, however, which will have to be considered in that specific population of patients.
Dr. Ebbert is professor of medicine, a general internist at the Mayo Clinic in Rochester, Minn., and a diplomate of the American Board of Addiction Medicine. The opinions expressed are those of the author. The opinions expressed in this article should not be used to diagnose or treat any medical condition nor should they be used as a substitute for medical advice from a qualified, board-certified practicing clinician.