Salt.

Image courtesy of Exsodus at FreeDigitalPhotos.net

Image courtesy of Exsodus at FreeDigitalPhotos.net

Salt (sodium) consumption is an interesting and convoluted topic. If you asked someone on the street about how much salt you’re supposed to have to be healthy they’d probably say something like, “Oh, less than I have. I don’t think you’re supposed to have much.”

The idea manifested in 1972 when the National High Blood Pressure Education Program started by the National Institutes of Health recommended a low sodium intake. At that time, the evidence supporting the assertion was weak.  In the subsequent almost half-century the scientific research hasn’t been clear either.

As Gary Taubes wrote for the New York Times, “In the years since, the N.I.H. has spent enormous sums of money on studies to test the hypothesis, and those studies have singularly failed to make the evidence any more conclusive. Instead, the organizations advocating salt restriction today — the U.S.D.A., the Institute of Medicine, the C.D.C. and the N.I.H. — all essentially rely on the results from a 30-day trial of salt, the 2001 DASH-Sodium study. It suggested that eating significantly less salt would modestly lower blood pressure; it said nothing about whether this would reduce hypertension, prevent heart disease or lengthen life.”

In 2013 The Institute of Medicine released a position paper suggesting that “The committee found no evidence for benefit and some evidence suggesting risk of adverse health outcomes associated with sodium intake levels in ranges approximately 1,500 to 2,300 mg/day among those with diabetes, kidney disease, or CVD. Further, the evidence on both the benefit and harm is not strong enough to indicate that these subgroups should be treated differently than the general U.S. population. Thus, the evidence on direct health outcomes does not support recommendations to lower sodium intake within these subgroups to or even below 1,500 mg/day.”

The idea behind restricting salt intake is based on body and kidney physiology. The idea that excess salt is harmful is not unreasonable.  High salt consumption causes the body to retain water in order to maintain a constant sodium concentration in the blood.  Salty foods make us thirsty, we drink more water and for a short period, blood pressure increases until the kidneys excrete the excess salt and water.  As high blood pressure is a risk factor for cardiovascular disease (CVD), the idea that chronic blood pressure increases caused by high salt consumption over time would increase CVD is reasonable.  The problem again is that there has been little evidence to support this idea.

Research about salt consumption is still murky. It’s looking like for people without high blood pressure there will probably be a minimum and a maximum recommendation for salt intake.  For those with high blood pressure, approximately 51% are responsive to salt consumption, so in those folks looking at their dietary salt would be beneficial.

As with most topics, this one is more complicated the deeper you go.  If you’re interested in looking at the research, check out the links below.

Thanks to Dr. Jacob Schor, ND, FABNO of Denver Naturopathic for his July 5, 2015 newsletter exploring this topic.

 

Resources

Schor, Jacob. How much Salt? July 5, 2015   http://denvernaturopathic.com/Salt.htm

https://www.nhlbi.nih.gov/files/docs/resources/heart/hbp_salt.pdf National High Blood Pressure Education Program: Implementing Recommendations for Dietary Salt Reduction.  NIH.  Publication No. 55-728N, Nov 1996.

Vollmer WM, Sacks FM, Ard J, Appel LJ, Bray GA, Simons-Morton DG, Conlin PR, et al. DASH-Sodium Trial Collaborative Research Group. Effects of diet and sodium intake on blood pressure: subgroup analysis of the DASH-sodium trial. Ann Intern Med. 2001 Dec 18;135(12):1019-28.

Taubes G.   Salt, We Misjudged You. New York Times. June 2, 2012.
http://www.nytimes.com/2012/06/03/opinion/sunday/we-only-think-we-know-the-truth-about-salt.html?_r=1
http://iom.nationalacademies.org/~/media/Files/Report%20Files/2013/Sodium-Intake-Populations/SodiumIntakeinPopulations_RB.pdf

http://medicalresearch.com/heart-disease/much-salt-intake-recommended-patients-heart-disease/10200/

Adler AJ, Taylor F, Martin N, Gottlieb S, Taylor RS, Ebrahim S. Reduced dietary salt for the prevention of cardiovascular disease. Cochrane Database Syst Rev. 2014 Dec 18;12:CD009217.

Graudal N, Jürgens 2, Baslund B, Alderman MH. Compared with usual sodium intake, low- and excessive-sodium diets areassociated with increased mortality: a meta-analysis. Am J Hypertens. 2014 Sep;27(9):1129-37.

Reinberg S. CDC salt guidelines too low for good health. HealthDay News, April 2, 2014.
http://www.webmd.com/food-recipes/20140402/cdc-salt-guidelines-too-low-for-good-health-study-suggests

http://www.cnpp.usda.gov/sites/default/files/dietary_guidelines_for_americans/ExecSumm.pdf

http://www.cspinet.org/new/pdf/jacn_letter_1.pdf

https://www.sciencenews.org/blog/food-thought/salty-controversy-over-sodium-and-health-papers

Merino J, Guasch-Ferré M, Martínez-González MA, Corella D, Estruch R, Fitó M, Ros E, Salas-Salvadó J, et al. Is complying with the recommendations of sodium intake beneficial for health in individuals at high cardiovascular risk? Findings from the PREDIMED study. Am J Clin Nutr. 2015 Mar;101(3):440-8.

Guasch-Ferré M, Bulló M, Martínez-González MÁ, Ros E, Corella D, Estruch R, Fitó M, Arós F, et al; PREDIMED study group. Frequency of nut consumption and mortality risk in the PREDIMED nutrition intervention trial. BMC Med. 2013 Jul 16;11:164.doi:10.1186/1741-7015-11-164.

Armando I, Villar VA, Jose PA. Genomics and Pharmacogenomics of Salt-sensitive Hypertension. Curr Hypertens Rev. 2015;11(1):49-56.

Robert P. Heaney. Making Sense of the Science of Sodium. Nutr Today. 2015 March; 50(2): 63–66. Published online 2015 March 26.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420255/pdf/nt-50-66.pdf

Anderson CA, Johnson RK, Kris-Etherton PM, Miller EA. Commentary on Making Sense of the Science of Sodium. Nutr Today. 2015 Mar;50(2):66-71.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420255/