Point/CounterpointThe Population Risks of Dietary Salt Excess Are Exaggerated
Section snippets
Sodium and BP: A Historical Overview
Dahl in the early 1960s showed that chronic excess salt ingestion led to sustained hypertension in rats who were fed extremely large amounts of salt.6 Only rats selectively bred to be “susceptible” to hypertensive responses to salt showed pronounced BP increases, whereas “resistant” rats did not.7 In 1970, a National Academy of Sciences committee concluded that the accumulated evidence incriminating salt as causing hypertension was inconclusive. Nevertheless, the food industry saw a market for
The Population Urban Rural Epidemiologic (PURE) Study
INTERSALT (with 10,000 individuals) was not large enough to assess the nature of the relationship (eg, whether the association is linear or nonlinear) between sodium and BP or the effects in key subpopulations (eg, hypertensive patients or different ethnic groups). To address these questions, a substantially larger study of sodium and BP would be needed.
Recently, new data were reported from the PURE study (presented at the European Society of Cardiology meeting in September 2013) on over
Is Sodium Reduction to Low Levels Feasible?
Some guidelines recommend reducing the sodium consumption of the general population to < 2.3 g/d, and some recommend reduction to even 1.5 g/d. Currently the average intake of sodium in Western populations is about 3.5-4.0 g of sodium per day. In the United States, only 9% of adults consume < 2.3 g/d, and just 0.6% consume < 1.5 g/d.17 In the PURE study of over 100,000 individuals globally,21 very few individuals consumed < 2300 mg of sodium, and practically none consumed < 1500 mg. This
Shortcomings of BP as a Surrogate to Predict Effects of Sodium Reduction on Clinical Outcomes
The contention that BP reductions, irrespective of the approach and the baseline level of BP, will translate into reduction of CVD reductions is not proved. For instance, recent trials showed that some agents reduce BP but have no effect on clinical outcomes,27 other agents reduce BP only modestly but produce a substantial reduction in CVD,28 and different agents reduce BP to similar extents and yet differ in their impact on CVD and individual CVD outcomes.29, 30 Further, even in high-risk
Shift in Focus From Surrogate Measures to Clinical Outcomes
In recent years, there has been a shift in focus from surrogate measures (eg, BP) to clinical outcomes (eg, MI, stroke, heart failure, CVD, and mortality).
Cohort studies
A 2009 meta-analysis of 13 prospective cohort studies that compared highest vs lowest quantiles of sodium intake among studies reported that a 2 g/d increase in sodium intake (5 g of salt) was associated with an increased risk of stroke (relative risk [RR], 1.23; 95% CI, 1.06-1.43) and composite of all CV events (RR, 1.14; 95% CI, 0.99-1.32).38 However, for both outcomes, there was significant heterogeneity across studies. Given the differing ranges of sodium intake of populations included in
Conclusions
The evidence supports a strong association between sodium and BP in individuals with hypertension, the elderly, and those who consume > 5-6 g/d of sodium. There is little impact on BP and clinical events at lower levels of consumption and concerns about harm at sodium intake < 3 g/d. Therefore, until new evidence (ideally from large RCTs) emerges, the optimal range of sodium consumption should be considered to be between 3 and 6 g/d. The vast majority of Canadians (94%) have sodium intakes < 6
Funding Sources
S.Y. holds the Heart and Stroke foundation/Marion W. Burke Chair in Cardiovascular Disease.
Disclosures
The authors have no conflicts of interest to disclose.
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Cited by (10)
Hypertension Due to Toxic White Crystals in the Diet: Should We Blame Salt or Sugar?
2016, Progress in Cardiovascular DiseasesCitation Excerpt :This is because sodium intake is regulated by the hypothalamus10 and trying to force a population to reduce their sodium intake to <2300 mg/day may be practically impossible. In fact, the intake of sodium across numerous countries over the last 50 years has remained in a very tight range (approximately 3.5–4 g of sodium per day) despite population-wide policies recommending sodium restriction.10,11 This suggests that the intake of sodium is indeed driven by physiology not by behavior or a hedonic drive.
Assessment of Dietary Sodium and Potassium in Canadians Using 24-Hour Urinary Collection
2016, Canadian Journal of CardiologyGlobal, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks in 188 countries, 1990-2013: A systematic analysis for the Global Burden of Disease Study 2013
2015, The LancetCitation Excerpt :On the other hand, the J-shaped curve could be due to residual confounding or reverse causation. The findings from PURE have generated much debate on the methods used to measure sodium intake, as well as the potential for low sodium intake to reduce blood pressure but raise mortality through some aspect of the renin–aldosterone system.49,65,66 While the debate on optimum sodium intake is likely to continue, even with a much wider TMREL, high sodium intake is a major global risk.
Dietary Sodium and Blood Pressure: How Low Should We Go?
2015, Progress in Cardiovascular DiseasesCitation Excerpt :According to the Dietary Guidelines for Americans, developed every five years based on in-depth, systematic, carefully conducted, quality controlled literature review, current dietary intake of sodium continues to exceed recommended amounts by the vast majority of the population across all age, sex, ethnic and economic groups.1 While current population-wide recommendations advocate less than 2300 mg sodium per day and worldwide recommendations advocate less than 2000 mg/d, questions regarding the merits of recommendations less than that have been raised.2–4 The 2010 US Dietary Guidelines Advisory Committee (USDGAC) and the American Heart Association (AHA) recommended sodium intake of 1500 mg for those who are over the age of 51, African American and/or already diagnosed with hypertension (HTN), but recent publications have questioned the validity of these recommendations and have even raised concerns about potential harm from dropping sodium intake below these levels.5–7
High sodium causes hypertension: Evidence from clinical trials and animal experiments
2015, Journal of Integrative Medicine
See article by Neal, pages 502-506 of this issue.
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