The researchers wrote:
"Extrapolations from observational studies and short-term intervention trials suggest that population-wide moderation of salt intake might reduce cardiovascular events. The assumption that lower salt intake would in the long run lower blood pressure, to our knowledge, has not yet been confirmed in longitudinal population-based studies."
Katarzyna Stolarz-Skrzypek, M.D., Ph.D., set out to determine whether rates of death, illness and hypertension might be linked to urinary sodium levels in a study involving 3,681 adults. None of them had cardiovascular disease when the study began. 2,096 had normal blood pressure when the study started while 1,499 had their urinary sodium levels and blood pressure monitored right through from beginning to the end of the 7.9-year follow up period.
People with high salt intake have higher urinary sodium levels than those with low salt intake.
Among all the participants that were followed up, 50 people with low urinary sodium died, compared to 24 deaths among the medium urinary sodium levels and 10 deaths among those with high levels of sodium in their urine - the three groups were fairly similar in numbers.
They found that cardiovascular mortality risk was much higher among those with the lowest levels of sodium in their urine.
The researchers added that they found no link between hypertension risk and high levels of sodium. In other words, those with a higher salt intake did not have a greater risk of developing high blood pressure.
The authors concluded:
"The associations between systolic pressure and sodium excretion did not translate into less morbidity or improved survival. On the contrary, low sodium excretion predicted higher cardiovascular mortality.
Taken together, our current findings refute the estimates of computer models of lives saved and health care costs reduced with lower salt intake. They do also not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level.
However, they do not negate the blood pressure-lowering effects of a dietary salt reduction in hypertensive patients."
The authors stressed that their population sample consisted mainly of Caucasian adults.
"Fatal and Nonfatal Outcomes, Incidence of Hypertension, and Blood Pressure Changes in Relation to Urinary Sodium Excretion"
Katarzyna Stolarz-Skrzypek, MD, PhD; Tatiana Kuznetsova, MD, PhD; Lutgarde Thijs, MSc; Valérie Tikhonoff, MD, PhD; Jitka Seidlerová, MD, PhD; Tom Richart, MD; Yu Jin, MD; Agnieszka Olszanecka, MD, PhD; Sofia Malyutina, MD, PhD; Edoardo Casiglia, MD, PhD; Jan Filipovský, MD, PhD; Kalina Kawecka-Jaszcz, MD, PhD; Yuri Nikitin, MD, PhD; Jan A. Staessen, MD, PhD
JAMA. 2011;305(17):1777-1785. doi: 10.1001/jama.2011.574