Salt Shake-up?
Shaking Out the Salt Conundrum
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Your patients are likely to ask you about a recent study published in JAMA that calls into question the conventional wisdom of limiting the population’s salt intake and the health effects of salt. The study’s take-home message? Patients with lower sodium intake (measured by sodium excretion) and without cardiovascular disease were associated with higher cardiovascular mortality. Conversely, higher sodium intake was not associated with an increased risk of hypertension or complications from cardiovascular disease.
Belgium-based researchers examined the incidence of death, illness, and hypertension in relation to measures of urinary sodium excretion, the best measure of sodium intake. The study included 3,681 participants without cardiovascular disease (CVD) at the beginning of the study. Of these, 2,096 had normal blood pressure at baseline and 1,499 had blood pressure and sodium excretion measured at baseline and last follow-up (2005-2008).
After a 7.9 year average, the investigators found that the less salt people consumed, the more likely they were to die of heart disease—50 people in the lowest third of salt consumption (2.5 grams of sodium per day) died during the study, as compared with 24 in the medium group (3.9 grams of sodium per day) and 10 in the highest salt consumption group (6.0 grams of sodium per day). And while those consuming the most salt had, on average, a slight increase in systolic blood pressure, they were no more likely to develop hypertension. The current United States recommendations call for no more than 2,300 milligrams of sodium a day and 1,500 milligrams of sodium for people who have high blood pressure or are at high risk of developing CVD.
This study was heavily covered in national print and electronic media; however, many news reports that ran the feature neglected to discuss flaws in the study.
With less than 4,000 participants who were 40 years old at the start of the study—and only 84 deaths due to CVD—the study is too small to support the authors’ sweeping conclusions. In addition, the study included only white Europeans; therefore the findings cannot be extrapolated for Asians or blacks, who might be more salt sensitive than whites.
The study also fails to account for key variables that influence sodium intake and heart disease, such as height, increased physical activity, and total calories consumed. People who are taller or more active tend to have a lower risk of heart disease, and they eat more, leading to higher sodium intakes. Because the authors didn’t account for these differences, it’s impossible to know whether high sodium, physical activity, or height is responsible for the decreased risk of CVD.
But perhaps the most glaring flaw in the study is that the investigators base their main findings on a single measurement of 24-hour sodium excretion collected at the start of the study. However, sodium excretion from just one day does not reflect peoples’ salt intake patterns over long periods of time. It’s considered flawed science to use a single, one-day sodium excretion to predict heart disease or mortality decades later.
The bottom line?
Overall, this study does not provide reliable evidence to rescind the current recommendations regarding salt. For those with high blood pressure, the standard advice still applies: maintain a healthy weight, avoid too much alcohol, remain physically active, and keep the salt intake to a minimum. There is also good evidence from the DASH (dietary approaches to stop hypertension) trials that in addition to maintaining a low-salt diet, there are additional benefits to having a diet rich in potassium, calcium, and magnesium; fruits, vegetables, and low-fat dairy; and whole grains.
Jill Shuman, MS, ELS
Published on May 10, 2011
Source: Stolarz-Skrzypek K, Kuznetsova T, Thijs L, et al. Fatal and nonfatal outcomes, incidence of hypertension, and blood pressure changes in relation to urinary sodium excretion. JAMA. 2011;305(17):1777-1785. doi:10.1001/jama.2011.574
poor designed study.
Still consider DASH diet is the best option for hypertensives instead of advising liberal salt intake.
more studies needed and also to include other ehtnic groups.