Has Salt Gotten a Bum Rap?

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According to a recent article published in the May 4, 2011 issue of Journal of the American Medical Association, and articles that appeared in the mass media in its wake, a higher sodium intake was associated with only a very modest increase in systolic blood pressure (BP) but a surprising yet very signifi- cant reduction in cardiovascular disease (CVD) deaths. In this study medical researchers fol- lowed 3681 middle-aged (mean about 40 years of age) Europeans without CVD at initial screening for 7.9 years. Sodium intake was estimated based on a single 24-hour urinary sodium excretion measurement. During the follow up period there were 50 deaths in the low sodium (2438mg/d), 24 in the medium sodium (3864mg/d) group, and only 10 in the high sodium (5980mg/d) excretion group. In this popula- tion, systolic blood pressure did increase modestly over time in those whose sodium excretion was higher initially, but this as- sociation did not translate into a higher risk of developing hypertension or CVD complications. Indeed, lower sodium excretion was significantly associated with higher CVD mortality.1 Does this new data mean population-wide efforts to reduce salt could be dangerous and increase CVD deaths? One of the study’s authors, Dr. Jan Staessen told WebMD: “Our finding refutes the estimates of computer models of lives saved and healthcare costs reduced with lower salt intake”. Perhaps not surprisingly Lori Roman president of the Salt Institute - a trade group that operates like the defunct Tobacco Institute - told WebMD “We now know conclusively that the US government’s war on salt consumption will cause harm.”

Certainly the Salt Institute would want have a financial incentive to use this study’s weird data to negate calls to reduce salt intake. Campbell’s Soup who helps fund the Salt Institute perhaps decid- ed to use this recent study’s data and media reports suggesting salt is perhaps “humm, humm good” after all as an excuse to add back the salt they had previ- ously removed from some of their soup lines. No doubt Camp- bell’s was concerned about lag- ging sales of their lower sodium soups and hopes adding back the salt will improve the taste and bring back lost customers.

Fortunately this European study has done nothing to slow efforts to reduce salt intake. Indeed, there are now 32 initiatives (most governmental) in countries around the World attempting to get the food industry and people to cut back on salt/sodium in order to reduce the incidence of hypertension and prevent heart disease and stroke. Indeed, data from 5 countries have already shown population-wide efforts to reduce salt are in fact result- ing in lower blood pressure and reduced CVD.2 The American Heart Association has not taken back their recent Presidential Advisory telling Americans to limit daily sodium intake to no more than 1,500mg per day.3 Indeed, the AHA advisory notes research showing that increased salt intake “...also has BP-inde- pendent effects, promoting left ventricular hypertrophy as well as fibrosis in the heart, kidneys, and arteries.4

Nor has the Center for Disease Control (CDC) rescinded their warning for all Americans over the age of 40 years to reduce their sodium intake to less than 1,500mg/d. Indeed, the CDC released a commentary on the European study and its authors’ suggestion that salt reduction might be dangerous.5 Dr. Bliss at the CDC noted that sodium in- take was estimated from a single 24-hour urine collection, which is very inaccurate even if done accurately as salt intake varies a lot from day to day. Perhaps his most telling criticism of the study was that “...the urine volumes and urine creatinine suggest that some of the people who were categorized in the low-sodium group may have had incomplete urine collections.” The most likely explanation for their lower urinary sodium levels was probably not a lower salt intake but rather noncompliance with the request to collect all their urine over 24 hours. If this is the case, the low sodium intake was not real and so the increased CVD associated with it may have more to do with the inability or unwilling- ness of the “low-sodium” group to comply with authority figures and medical advice. Defiance of medical advice to take medications to lower CVD risk could certainly increase CVD events and this is a more likely explanation for the increased CVD deaths in the “lowest sodium” group.

By James J. Kenney, PhD, FACN

References:

1. JAMA 2011;305:1777-85 2. J Hypertens 2011;29:1043-50 3. Circulation 2011;123:1138-43 4. Hypertension 2007;50:161-6 5. http://www.medscape.com/viewarticle/743642?src=mp&sp on=7

For more information on salt toxicity, see foodandhealth.com and click on CPE courses at the top. Click on Salt Toxicity to see a comprehensive paper on all salt research to date with over 200 references cited. Dr. Kenney has a list of risks on the salt page.

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