Dietary Salt and Health

For decades people have been advised to avoid salt in their diet as a method of keeping blood pressure at lower levels.  Guidelines promulgated by specialty societies and disease organizations have suggested very low consumption of salt, which would reduce sodium levels in the blood and body.  Now some studies are indicating that these low sodium levels may lead to adverse health events.  This research and some accompanying commentary were recently published in the New England Journal of Medicine.  (NEJM Article) (NEJM Article) (NEJM Article)  Hypertension is estimated to affect one billion people worldwide, although like many diseases, new definitions about who has high blood pressure have greatly expanded the patient pool, which makes drug companies happy.  An Institute of Medicine expert panel concluded that there is a relationship between high salt (sodium) intake and risk of cardiovascular disease, but also found that low sodium intake may be associated with either increased or decreased risk.  But one of the large observational studies reported in the NEJM evaluated more than 100,000 adults from 17 countries and found that while high dietary salt is related to higher levels of blood pressure, low salt use was not, meaning that just getting people to lower sodium levels may not be beneficial.  And sodium levels may be related to low potassium levels, leading to undesirable health events.  So diets need to have a balance between lowering sodium levels but keeping potassium higher.

The underlying lesson here is that science is rarely “settled”, in health care or anything else, and that making recommendations on less than thorough scientific data can be dangerous.  Our guideline crazy health system now has seen several examples of later research undermining recommendations that were widely publicized and that often are the basis for pay-for-performance and value-based purchasing programs.  Physicians and other health care providers need to be given more help in understanding just how rigorous the science behind various guidelines is and they need more latitude to use judgment about the effect of following guidelines on individual patients.  And patients need to be mindful of caveat emptor in regard to guidelines.