Pass the Salt – Risks Linked to Low Salt Diet?
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%.
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
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