Salt and cardiovascular disease: insufficient evidence to recommend low sodium intake.

Several blood pressure guidelines recommend low sodium intake (<2.3 g/day, 100 mmol, 5.8 g/day of salt) for the entire population, on the premise that reductions in sodium intake, irrespective of the levels, will lower blood pressure, and, in turn, reduce cardiovascular disease occurrence. These guidelines have been developed without effective interventions to achieve sustained low sodium intake in free-living individuals, without a feasible method to estimate sodium intake reliably in individuals, and without high-quality evidence that low sodium intake reduces cardiovascular events (compared with moderate intake). In this review, we examine whether the recommendation for low sodium intake, reached by current guideline panels, is supported by robust evidence. Our review provides a counterpoint to the current recommendation for low sodium intake and suggests that a specific low sodium intake target (e.g. <2.3 g/day) for individuals may be unfeasible, of uncertain effect on other dietary factors and of unproven effectiveness in reducing cardiovascular disease. We contend that current evidence, despite methodological limitations, suggests that most of the world's population consume a moderate range of dietary sodium (2.3-4.6g/day; 1-2 teaspoons of salt) that is not associated with increased cardiovascular risk, and that the risk of cardiovascular disease increases when sodium intakes exceed 5 g/day. While current evidence has limitations, and there are differences of opinion in interpretation of existing evidence, it is reasonable, based upon observational studies, to suggest a population-level mean target of <5 g/day in populations with mean sodium intake of >5 g/day, while awaiting the results of large randomized controlled trials of sodium reduction on incidence of cardiovascular events and mortality.

The significance of duration and amount of sodium reduction intervention in normotensive and hypertensive individuals: a meta-analysis.

The purpose of this meta-analysis was to establish the time for achievement of maximal blood pressure (BP) efficacy of a sodium reduction (SR) intervention and the relation between the amount of SR and the BP response in individuals with hypertension and normal BP. Relevant studies were retrieved from a pool of 167 randomized controlled trials (RCTs) published in the period 1973-2010 and integrated in meta-analyses. Fifteen relevant RCTs were included in the maximal efficacy analysis. After initiation of sodium reduction (range: 55-118 mmol/d), there were no significant differences in systolic blood pressure (SBP) or diastolic blood pressure (DBP) between measurements at weeks 1 and 2 (∆SBP: -0.18 mmHg/∆DBP: 0.12 mmHg), weeks 1 and 4 (∆SBP: -0.50 mmHg/∆DBP: 0.35 mmHg), weeks 2 and 4 (∆SBP: -0.20 mmHg/∆DBP: -0.10 mmHg), weeks 2 and 6 (∆SBP: -0.50 mmHg/∆DBP: -0.42 mmHg), and weeks 4 and 6 (∆SBP: 0.39 mmHg/∆DBP: -0.22 mmHg). Eight relevant RCTs were included in the dose-response analysis, which showed that within the established usual range of sodium intake [<248 mmol/d (5700 mg/d)], there was no relation between the amount of SR (range: 136-188 mmol) and BP outcome in normotensive populations [∆SBP: 0.99 mm Hg (95% CI: -2.12, 4.10 mm Hg), [corrected] P = 0.53; ∆DBP: -0.49 mm Hg (95% CI: -4.0, 3.03), P = 0.79]. In contrast, prehypertensive and hypertensive populations showed a significant dose-response relation (range of sodium reduction: 77-140 mmol/d) [∆SBP: 6.87 mmHg (95% CI: 5.61, 8.12, P < 0.00001); ∆DBP: 3.61 mmHg (95% CI: 2.83, 4.39, P < 0.00001)]. Consequently, the importance of kinetic and dynamic properties of sodium reduction, as well as baseline BP, should probably be considered when establishing a policy of sodium reduction.

What determines human sodium intake: policy or physiology?

Past and current U.S. sodium and health policy focused on population-wide reductions in sodium intake. Underlying that policy are a number of assumptions that recent scientific publications challenged. The assumptions include the following: 1) that current intakes are excessive; 2) that the "healthy range" must be below current intakes; 3) that sodium intake can be substantially reduced by public policy; 4) that human intake is dictated by the sodium content of the food supply; and 5) that, unlike all other essential nutrients in which a healthy range is defined by a Gaussian distribution, lower sodium intake is always better. Drawing on the most current published evidence, this review addresses each of these long-standing assumptions. Based on worldwide surveys that assessed sodium intake by 24-h urinary sodium measurements, it is now evident that, across 45 societies and 5 decades, humans consume a reproducible, narrow range of sodium: ∼2600­4800 mg/d. This range is independent of the food supply, verifiable in randomized controlled trials, consistent with the physiologic regulators of sodium intake and is not modifiable by public policy interventions. These findings indicate that human sodium intake is controlled by physiology and cannot be modified by public health policies.

Normal range of human dietary sodium intake: a perspective based on 24-hour urinary sodium excretion worldwide.

BACKGROUND: The recommendation to restrict dietary sodium for management of hypertensive cardiovascular disease assumes that sodium intake exceeds physiologic need, that it can be significantly reduced, and that the reduction can be maintained over time. In contrast, neuroscientists have identified neural circuits in vertebrate animals that regulate sodium appetite within a narrow physiologic range. This study further validates our previous report that sodium intake, consistent with the neuroscience, tracks within a narrow range, consistent over time and across cultures. METHODS: Peer-reviewed publications reporting 24-hour urinary sodium excretion (UNaV) in a defined population that were not included in our 2009 publication were identified from the medical literature. These datasets were combined with those in our previous report of worldwide dietary sodium consumption. RESULTS: The new data included 129 surveys, representing 50,060 participants. The mean value and range of 24-hour UNaV in each of these datasets were within 1 SD of our previous estimate. The combined mean and normal range of sodium intake of the 129 datasets were nearly identical to that we previously reported (mean = 158.3±22.5 vs. 162.4±22.4 mmol/d). Merging the previous and new datasets (n = 190) yielded sodium consumption of 159.4±22.3 mmol/d (range = 114-210 mmol/d; 2,622-4,830mg/d). CONCLUSIONS: Human sodium intake, as defined by 24-hour UNaV, is characterized by a narrow range that is remarkably reproducible over at least 5 decades and across 45 countries. As documented here, this range is determined by physiologic needs rather than environmental factors. Future guidelines should be based on this biologically determined range.

Community-based priorities for improving nutrition and physical activity in childhood.

Overweight among America's youth has prompted a large response from foundations, government, and private organizations to support programmatic interventions. The architecture for many of these programs was derived from "experts," whereas the perspective of families, and communities--those most affected and most instrumental in altering behavior--is rarely the driving force. Shaping America's Youth (SAY) was established to assess programs that target nutrition and physical activity and to promote the necessary family and community input. In a 2004 report, SAY documented how community efforts are motivated, funded, structured, and evaluated. It identified discordance between that effort and the opinions of experts. To ensure that the voices of families and communities are integrated into such local and national policies and programs, SAY initiated a unique series of 5-day-long town meetings, input from which was independently statistically analyzed. Across a range of demographics, the results indicated that participants perceive the barriers and solutions similarly. There was broad agreement that the family has primary responsibility, starting with a need to focus on improved quality and duration of family time directed at nutrition and activity. Concurrently they identified needed actions from external sources, including clear and consistent nutrition information; ready access to healthy foods; and a built environment that promotes physical activity. Rather than one-dimensional or governmental solutions, they expressed a need for community-based partnerships integrating health care, education, environment, government, and business. Although this citizen-engagement process did not identify specific actions, it defined basic steps that communities must integrate into future approaches.