Pass the Salt – Risks Linked to Low Salt Diet?




Salt shaker on table

In light of the fact that approximately 90% of all Americans will develop high blood pressure during their lifetime, the American Heart Association recommends a daily intake of no more than 1,500 milligrams of sodium to reduce the risk of high blood pressure, heart attacks, stroke, and kidney disease. However, results published in the Journal of the American Medical Association (JAMA) from a recent European study coordinated in Belgium have challenged the notion that a reduced sodium (salt) consumption lowers the risk of heart attacks, congestive heart failure, and stroke.

In a prospective, population-based cohort study, researchers tested urinary sodium excretion in 3,681 people without cardiovascular disease (CVD) (average age 40) for approximately 8 year to assess whether 24-hour urinary sodium excretion predicts blood pressure and health outcomes. According to JAMA, the study concluded that “systolic blood pressure, but not diastolic pressure, changes over time aligned with change in sodium excretion, but this association did not translate into a higher risk of hypertension or CVD complications. Lower sodium excretion was associated with higher CVD mortality.” The study results revealed that the systolic blood pressure was slightly lower in those who excreted less sodium, but, surprisingly, those with lower sodium excretion had an increased risk of cardiovascular death. The study results were consistent in participants younger and older than 60 years.

According to Dr. Jan Staessen, a professor of medicine at the University of Leuven in Belgium and one of the study authors, the study does not promote a reduction of salt consumption for everyone and states that, “Lower sodium intake is recommended for people with high blood pressure and people with heart failure, but recommending it to the population as a whole, I wouldn’t do without proving it’s completely safe.” He acknowledges a limitation of the study and states that while the study may apply to Americans of white European descent, it might less applicable to the black population since they are believed to be more salt sensitive.

Staessen explains, “If one lowers sodium intake to lower blood pressure, this change in sodium activates several systems (including the renin-angiotensin aldosterone system) that conserve sodium, and those systems are implicated in disease processes such as damaging the arterial wall and kidneys.”

The study results have been met with criticism from medical experts and other studies have also concluded that sodium reduction results in decreased cardiovascular disease risk in the general population. Ralph Sacco, president of the American Heart Association and chairman of neurology at the University of Miami said, “We have based our recommendations on the many scientific studies which show a strong relationship between reduced sodium consumption and a lower risk of heart attacks, congestive heart failure and stroke.” He contends, “There are good randomized, controlled studies – the gold standard of scientific studies – that show a lower sodium diet has a meaningful effect on blood pressure.”

According to the Centers for Disease Control and Prevention (CDC), the Dietary Guidelines for Americans 2005 recommends that specific groups, including individuals with hypertension, all middle-aged and older adults, and all blacks should limit intake to 1,500 mg/day of sodium. These specific groups include approximately 70% of the adult population in the United States. The recommended limit for all other adults is less than 2,300 mg/day of sodium. Processed and restaurant foods are the largest source of dietary sodium intake (77%) in the United States, while table salt and cooking accounts for 10%.

References

Stolarz-Skrzypek K, Kuznetsova T, Thijs L, Tikhonoff V, Seidlerová J, Richart T, Jin Y, Olszanecka A, Malyutina S, Casiglia E, Filipovský J, Kawecka-Jaszcz K, Nikitin Y, Staessen JA, & European Project on Genes in Hypertension (EPOGH) Investigators (2011). Fatal and nonfatal outcomes, incidence of hypertension, and blood pressure changes in relation to urinary sodium excretion. JAMA : the journal of the American Medical Association, 305 (17), 1777-85 PMID: 21540421

Morrison AC, & Ness RB (2011). Sodium intake and cardiovascular disease. Annual review of public health, 32, 71-90 PMID: 21219163

Centers for Disease Control and Prevention (CDC) (2010). Sodium intake among adults – United States, 2005-2006. MMWR. Morbidity and mortality weekly report, 59 (24), 746-9 PMID: 20577156

Krzesinski JM (2009). [Sodium and arterial hypertension --one hundred years of controversies]. Bulletin et memoires de l’Academie royale de medecine de Belgique, 164 (3-4) PMID: 20120089

Mattes RD, & Donnelly D (1991). Relative contributions of dietary sodium sources. Journal of the American College of Nutrition, 10 (4), 383-93 PMID: 1910064

  • http://Biowizardry.blogspot.com Isabel (retired ER/ICU RN)

    I’m glad they used urine sodium, as that provides a better reflection of the intracellular state than serum sodium, which reflects extracellular levels. Both would have been most meaningful, as it’s the intra/extracellular dynamic that the clinicians really need to pay attention to. If they really wanted to see what the chemical picture of survival looked like, though, they would have checked a few more electrolytes. 

    As for the American figures, it would be nice if statistics meant anything in the case of the individual. 

    It would be even nicer if scientists were better clinicians. Then we’d have more useful and comprehensive guidelines. And more meaningful tests used in these studies. 

    The longstanding medical fashion for low-salt diets has not yet led to a corresponding understanding of these dynamics in practice. Attentive nurses and physicians know that you have to protect the sodium/potassium balance even more assiduously than the acid/base balance, if you want your heart patient to survive. The lack of any mention of the role of potassium here is a horrifying omission, clinically speaking. It’s not a trivial issue or an afterthought; it’s the keystone to survival. 

    Sounder electrolyte studies would have shown this more clearly. They’d also make a much better case for people not only cutting down on salt, but eating their fruits and vegetables — thus boosting adequate potassium, protecting the acid/base balance, and improving both urinary and intestinal elimination. Just by changing their approach to produce. 

    Now THAT’s good medicine. 

Angela M Sexton, PharmD

Angela M Sexton, PharmD, is a licensed pharmacist and freelance medical writer with experience in clinical pharmacy, retail pharmacy, and pharmacovigilance in both the United States and Europe. She is an honors graduate of The Samford University McWhorter School of Pharmacy with a Doctor of Pharmacy degree and also earned a bachelor’s degree in biology from the University of Alabama. Her professional interests include traditional pharmaceutical therapies, immunizations, and preventative health initiatives.
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