Compendium of the most significant studies with reference to properties, intake, effects.

Salt and hypertension

Morowatisharifabad MA, Salehi-Abargouei A, Mirzaei M, Rahimdel T. Behavioral beliefs of reducing salt intake from the perspective of people at risk of hypertension: An exploratory study. ARYA Atheroscler. 2019 Mar;15(2):59-66. doi: 10.22122/arya.v15i2.1900. 

Abstract. This study was a TPB-based exploratory research. The participants were 25 married individuals at risk of developing HTN, with a mean age of 42.9 ± 7.2 years. They were selected by purposive maximum variation sampling continued until data saturation. The data collection method was a semi-structured interview. Study lasted from January 2017 to April 2017.

Grillo A, Salvi L, Coruzzi P, Salvi P, Parati G. Sodium Intake and Hypertension. Nutrients. 2019 Aug 21;11(9):1970. doi: 10.3390/nu11091970. 

Abstract. The close relationship between hypertension and dietary sodium intake is widely recognized and supported by several studies. A reduction in dietary sodium not only decreases the blood pressure and the incidence of hypertension, but is also associated with a reduction in morbidity and mortality from cardiovascular diseases. Prolonged modest reduction in salt intake induces a relevant fall in blood pressure in both hypertensive and normotensive individuals, irrespective of sex and ethnic group, with larger falls in systolic blood pressure for larger reductions in dietary salt. The high sodium intake and the increase in blood pressure levels are related to water retention, increase in systemic peripheral resistance, alterations in the endothelial function, changes in the structure and function of large elastic arteries, modification in sympathetic activity, and in the autonomic neuronal modulation of the cardiovascular system. In this review, we have focused on the effects of sodium intake on vascular hemodynamics and their implication in the pathogenesis of hypertension.

D'Elia L, La Fata E, Giaquinto A, Strazzullo P, Galletti F. Effect of dietary salt restriction on central blood pressure: A systematic review and meta-analysis of the intervention studies. J Clin Hypertens (Greenwich). 2020 May;22(5):814-825. doi: 10.1111/jch.13852.

Abstract. Central blood pressure (cBP) is highly associated with cardiovascular risk. Although reduction of salt intake leads to lower peripheral blood pressure (BP), the studies on cBP provided inconsistent results. Therefore, we performed a systematic review and a meta-analysis of the available intervention trials of salt reduction on cBP values to reach definitive conclusions. 

Khan MS, Jones DW, Butler J. Salt, No Salt, or Less Salt for Patients With Heart Failure? Am J Med. 2020 Jan;133(1):32-38. doi: 10.1016/j.amjmed.2019.07.034.

Abstract.  In this review we discuss the pros and cons of sodium restriction for patients with heart failure from the current literature.

Salt diet

Barone M, Turroni S, Rampelli S, Soverini M, D'Amico F, Biagi E, Brigidi P, Troiani E, Candela M. Gut microbiome response to a modern Paleolithic diet in a Western lifestyle context. PLoS One. 2019 Aug 8;14(8):e0220619. doi: 10.1371/journal.pone.0220619. 

Abstract. The modern Paleolithic diet (MPD), featured by the consumption of vegetables, fruit, nuts, seeds, eggs, fish and lean meat, while excluding grains, dairy products, salt and refined sugar, has gained substantial public attention in recent years because of its potential multiple health benefits. However, to date little is known about the actual impact of this dietary pattern on the gut microbiome (GM) and its implications for human health. In the current scenario where Western diets, low in fiber while rich in industrialized and processed foods, are considered one of the leading causes of maladaptive GM changes along human evolution, likely contributing to the increasing incidence of chronic non-communicable diseases, we hypothesize that the MPD could modulate the Western GM towards a more "ancestral" configuration. In an attempt to shed light on this, here we profiled the GM structure of urban Italian subjects adhering to the MPD, and compared data with other urban Italians following a Mediterranean Diet (MD), as well as worldwide traditional hunter-gatherer populations from previous publications. Notwithstanding a strong geography effect on the GM structure, our results show an unexpectedly high degree of biodiversity in MPD subjects, which well approximates that of traditional populations. The GM of MPD individuals also shows some peculiarities, including a high relative abundance of bile-tolerant and fat-loving microorganisms. The consumption of plant-based foods-albeit with the exclusion of grains and pulses-along with the minimization of the intake of processed foods, both hallmarks of the MPD, could therefore contribute to partially rewild the GM but caution should be taken in adhering to this dietary pattern in the long term.

Barić L, Drenjančević I, Matić A, Stupin M, Kolar L, Mihaljević Z, Lenasi H, Šerić V, Stupin A. Seven-Day Salt Loading Impairs Microvascular Endothelium-Dependent Vasodilation without Changes in Blood Pressure, Body Composition and Fluid Status in Healthy Young Humans. Kidney Blood Press Res. 2019;44(4):835-847. doi: 10.1159/000501747.

Abstract. We aimed to assess whether a 7-day high-salt (HS) diet affects endothelium-dependent and/or endothelium-independent microvascular function in the absence of changes in arterial blood pressure (BP), and to determine whether such microvascular changes are associated with changes in body composition and fluid status in healthy young humans.

McCubbin AJ, Lopez MB, Cox GR, Caldwell Odgers JN, Costa RJS. Impact of 3-day high and low dietary sodium intake on sodium status in response to exertional-heat stress: a double-blind randomized control trial. Eur J Appl Physiol. 2019 Sep;119(9):2105-2118. doi: 10.1007/s00421-019-04199-2.

Abstract. To determine the impact of altering dietary sodium intake for 3 days preceding exercise on sweat sodium concentration [Na+], and cardiovascular and thermoregulatory variables.

Cashman KD, Kenny S, Kerry JP, Leenhardt F, Arendt EK. 'Low-Salt' Bread as an Important Component of a Pragmatic Reduced-Salt Diet for Lowering Blood Pressure in Adults with Elevated Blood Pressure. Nutrients. 2019 Jul 26;11(8):1725. doi: 10.3390/nu11081725.

Abstract. Reformulation of bread in terms of salt content remains an important measure to help achieve a reduction in salt intake in the population and for the prevention of hypertension and elevated blood pressure (BP). Our fundamental studies on the reduction of salt on dough and bread characteristics showed that wheat breads produced with 0.3 g salt/100 g ("low-salt") were found to be comparable quality to that produced with the typical level of salt (1.2%). This food-based intervention trial examined, using a 5 week cross-over design, the potential for inclusion of "low-salt" bread as part of a pragmatic reduced-salt diet on BP, markers of bone metabolism, and plasma lipids in 97 adults with slightly to moderately elevated BP. Assuming all sodium from dietary intake was excreted through the urine, the intake of salt decreased by 1.7 g/day, on average, during the reduced-salt dietary period. Systolic BP was significantly lower (by 3.3 mmHg on average; p < 0.0001) during the reduced-salt dietary period compared to the usual-salt dietary period, but there was no significant difference (p = 0.81) in diastolic BP. There were no significant differences (p > 0.12, in all cases) in any of the urinary- or serum-based biochemical indices of calcium or bone metabolism or in plasma lipids between the two periods. In conclusion, a modest reduction in dietary salt intake, in which the use of "low-salt" (i.e., 0.3 g/100g) bread played a key role along with dietary advice, and led to a significant, and clinically meaningful, decrease in systolic, but not diastolic, BP in adults with mildly to moderately elevated BP.

Laverty AA, Kypridemos C, Seferidi P, Vamos EP, Pearson-Stuttard J, Collins B, Capewell S, Mwatsama M, Cairney P, Fleming K, O'Flaherty M, Millett C. Quantifying the impact of the Public Health Responsibility Deal on salt intake, cardiovascular disease and gastric cancer burdens: interrupted time series and microsimulation study. J Epidemiol Community Health. 2019 Sep;73(9):881-887. doi: 10.1136/jech-2018-211749. 

Abstract. In 2011, England introduced the Public Health Responsibility Deal (RD), a public-private partnership (PPP) which gave greater freedom to the food industry to set and monitor targets for salt intakes. We estimated the impact of the RD on trends in salt intake and associated changes in cardiovascular disease (CVD) and gastric cancer (GCa) incidence, mortality and economic costs in England from 2011-2025.

Sodium Chloride is a metal halide, the inorganic sodium salt of hydrochloric acid and the main component of common salt.

Industrially it appears as a white granular or fine, water-soluble powder.

What it is used for and where

Food

It is recommended to reduce salt consumption as it may cause damage to the cardiovascular system and increase the values of harmful LDL-cholesterol and cause hypertension, obesity and other serious diseases, but there is also diet salt on the market, with a lower percentage of sodium. 

'Salt killer'. This was the title of a well-known and authoritative American newspaper some time ago, explaining in detail the reasons why the overuse of common table salt could cause serious damage to health. In fact, salt is found naturally in almost all foods, so we absorb it daily, but heavy consumption can damage the human body. 

Hypertension: The relationship between salt and hypertension is unequivocal (1), and especially for the elderly, consumption must be reduced (2). For young people, the problems may be minor, but still exist (3). 

Obesity : High salt consumption is associated with overweight and obesity (4). 

Drinks and chips : The amount of salt in drinks, crisps etc. should be controlled, as the combination of salt and sugar (as not only sugar is included, but fructose, dextrose and others) can increase the risk associated with high salt consumption (5). 

Osteoporosis: In this study, despite press campaigns to advise against salt consumption, the results proved rather disappointing (6). The title of the article sums it up well: Important element, but invisible threat. 

So, to summarise, salt is an indispensable element, but one must be very careful not to abuse it. 

Salt is used as a food preservative

Cosmetics

In cosmetics, sodium chloride has the function of increasing the moisturising efficacy of ageing skin, is a thickener in shampoos and conditioners, but is also a co-factor in the eye irritation experienced with most shampoos and can cause dryness and itching of the scalp (7). Skin sodium is a pathophysiological feature of psoriasis (8), a chronic inflammatory skin disease, so high concentrations of sodium chloride should not be present in cosmetic products.

Medical

Sodium chloride is used in numerous medical and pharmaceutical applications: preservative, hypertonic salt solution in conjunction with dextran, production of interleukin-4, antibacterial with biocidal effect against Staphylococcus aureus (9).

Human epidermal stem cells can be stored in anhydrous sodium chloride at room temperature for months as well as some resident immune cells and skin fibroblasts (10).

The most relevant studies on this chemical compound have been selected with a summary of their contents:

Sodium Chloride studies

Typical commercial product characteristics Sodium Chloride

Appearance	White powder
Boiling Point	1461 ºC
Melting Point	801°C(lit.)
Flash Point	1413°C
Density	2.165      1.199 g/mL at 20 °C
Refraction Index	n20/D 1.378
Water Solubility	360 g/L (20 ºC)
Storage	+15C to +30C
Potassium Iodate	35±15(20-50) mg/kg
Potassium ferrocyanide	≤10.0
Pb	≤1.0
As	≤0.5
F	≤5.0
Fe	≤0.0002
Ferrous cyanide	≤0.0001
Ba	≤15
Nitrogen	≤0.001
Sulfate	≤0.002
Nitrite	0
Safety

• Molecular Formula  NaCl    ClNa
• Molecular Weight     58.44
• Exact Mass    57.958622
• CAS  7647-14-5
• UNII    451W47IQ8X
• EC Number   231-598-3
• DSSTox Substance ID    DTXSID3021271    DTXSID6040379    DTXSID501033754
• IUPAC  sodium;chloride
• InChI=1S/ClH.Na/h1H;/q;+1/p-1
• InChl Key      FAPWRFPIFSIZLT-UHFFFAOYSA-M
• SMILES   [Na+].[Cl-]
• MDL number  MFCD00003477
• PubChem Substance ID    329824637
• ChEBI  26710
• RXCUI    9863  
• NSC   77364
• RTECS   VZ4725000
• NCI   C29974    C821
• Beilstein    3534976
• NACRES NA.21

Synonyms

• Sodium chloride
• Salt

References_______________________________________________________________________

(1) Patience S. Understanding the relationship between salt intake and hypertension. Nurs Stand. 2013 Jan 2-8;27(18):45-7. doi: 10.7748/ns2013.01.27.18.45.c9487. 

Abstract. Hypertension is a public health problem that contributes significantly to the non-communicable disease burden. A review of the epidemiological literature demonstrates that the relationship between salt and hypertension is unequivocal. The Department of Health has reported some success promoting awareness of the need to reduce salt consumption, but more work needs to be done in this area.

(2) Borghi C, Tartagni E. The older patient with hypertension: care and cure. Ther Adv Chronic Dis. 2012 Sep;3(5):231-6. doi: 10.1177/2040622312452189. 

Abstract. Hypertension is one of the most important clinical conditions affecting older people. Its prevalence in this group of subjects is above 60% and continues to grow. Isolated systolic hypertension accounts for the majority of cases as systolic blood pressure increases with advancing age, while diastolic blood pressure remains unchanged or even decreases. Nowadays hypertension is a well established risk factor for stroke and cardiovascular disease among older people and its treatment is considered mandatory. The general recommended blood pressure goal in uncomplicated hypertension is less than 140/90 mmHg, even if this target in older people is based mainly on expert opinion. All patients should receive nonpharmacological treatment, in particular reduction in excess body weight when body mass index is greater than 26 kg/m(2) and dietary salt restriction. Older patients with hypertension may also benefit from smoking cessation, physical activity and alcohol restriction. In relation to drug therapy, a low-dose thiazide diuretic could be a good first step. Other first-line drugs are long-acting calcium channel blockers, generally dihydropyridines, and angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. The HYVET study showed a specific protective effect of indapamide with or without perindopril in people older than 80 years. Since monotherapy normalizes blood pressure in only 40-50% of cases, a combination of two or more drugs is often required. Moreover the addiction of a second drug may reduce the dose-related adverse effects of the first one. Finally, compliance with treatment should always be achieved by giving complete information to patients and simplifying the drug regimen as much as possible.

He FJ, Campbell NR, MacGregor GA. Reducing salt intake to prevent hypertension and cardiovascular disease. Rev Panam Salud Publica. 2012 Oct;32(4):293-300. doi: 10.1590/s1020-49892012001000008.

Abstract. There is compelling evidence that dietary salt intake is the major cause of raised blood pressure (BP) and that a reduction in salt intake from the current level of ≈ 9 - 12 g/day in most countries to the recommended level of < 5 g/day lowers BP. A further reduction to 3 - 4 g/day has a greater effect and there needs to be ongoing consideration of lower targets for population salt intake. Cohort studies and outcome trials have demonstrated that a lower salt intake is related to a reduced risk of cardiovascular disease. Salt reduction is one of the most cost-effective measures to improve public health worldwide. In the Americas, a salt intake of > 9 g/day is highly prevalent. Sources of salt in the diet vary hugely among countries; in developed countries, 75% of salt comes from processed foods, whereas in developing countries such as parts of Brazil, 70% comes from salt added during cooking or at the table. To reduce population salt intake, the food industry needs to implement a gradual and sustained reduction in the amount of salt added to foods in developed countries. In developing countries, a public health campaign plays a more important role in encouraging consumers to use less salt coupled with widespread replacement of salt with substitutes that are low in sodium and high in potassium. Numerous countries in the Americas have started salt reduction programs. The challenge now is to engage other countries. A reduction in population salt intake will result in a major improvement in public health along with major health-related cost savings.

(3) Campagnoli T, Gonzalez L, Santa Cruz F. Salt intake and blood pressure in the University of Asuncion-Paraguay youths: a preliminary study. J Bras Nefrol. 2012 Oct-Dec;34(4):361-8. doi: 10.5935/0101-2800.20120026. 

Abstract. Introduction: High salt intake is a major risk factor related to many cardiovascular and renal diseases. World Action on Salt and Health is a newly formed coalition of heath professionals whose goal is to implement changes in salt consumption in their respective countries for the goal of reducing blood pressure. In the same vein, we have decided to study the amount of salt intake in Paraguay to determine if a relationship exists between salt intake and blood pressure. Objective: A preliminary study was undertaken to determine salt intake in Paraguay and its relationship with blood pressure, in order to implement a national program to combat hypertension.... Conclusion: Salt intake and blood pressure were found to be significantly elevated in young adults in Paraguay and argues for the importance of instituting a national campaign to reduce salt intake in this society.

(4) Woodruff SJ, Fryer K, Campbell T, Cole M. Associations among blood pressure, salt consumption and body weight status of students from south-western Ontario. Public Health Nutr. 2014 May;17(5):1114-9. doi: 10.1017/S1368980013000335.

Abstract. Objective: The purpose was to examine the associations among body weight status, blood pressure and daily Na intake among grade 7 students from south-western Ontario, Canada. Design: Cross-sectional. Data were collected using the Food Behaviour Questionnaire, including a 24 h diet recall. Measured height and weight were used to determine BMI. Blood pressure was taken manually using mercury sphygmomanometers.... Conclusions: High intakes of Na, coupled with high SBP and DBP, were associated with overweight and obesity status among the grade 7 sample from south-western Ontario, Canada.

(5) Grimes CA, Riddell LJ, Campbell KJ, Nowson CA. Dietary salt intake, sugar-sweetened beverage consumption, and obesity risk. Pediatrics. 2013 Jan;131(1):14-21. doi: 10.1542/peds.2012-1628.

Abstract. Objective: To determine the association among dietary salt, fluid, and sugar-sweetened beverage (SSB) consumption and weight status in a nationally representative sample of Australian children aged 2 to 16 years....Conclusions: Dietary salt intake predicted total fluid consumption and SSB consumption within consumers of SSBs. Furthermore, SSB consumption was associated with obesity risk. In addition to the known benefits of lowering blood pressure, salt reduction strategies may be useful in childhood obesity prevention efforts.

(6) Wick JY. Salt: important element, invisible menace. Consult Pharm. 2012 Nov;27(11):756-62. doi: 10.4140/TCP.n.2012.756.

(7) Staszak K, Wieczorek D, Michocka K. Effect of Sodium Chloride on the Surface and Wetting Properties of Aqueous Solutions of Cocamidopropyl Betaine. J Surfactants Deterg. 2015;18(2):321-328. doi: 10.1007/s11743-014-1644-8.

Abstract. Surfactants are important ingredients of personal care products and household products. The main characteristic of these compounds is to decrease the surface tension of solvent and resulting many properties such as contact angle, foam properties etc. The coexistence of other ingredients in the product may affect the properties of surfactants. One of the main components contained in almost every personal care and household product is sodium chloride. The main aim of this work was to determine the effect of this salt on some surface and usage properties of cocamidopropyl betaine (CAPB). From our experiments it was shown that the effect of added sodium chloride in the aqueous solutions of CAPB on the properties is the opposite to the one described in the literature for cationic and anionic surfactants, i.e., CMC increases with increasing ionic strength, foam height decreases with increasing salt concentration. Our investigation showed that sodium chloride makes worse the properties of the CAPB solutions examined in this work.

(8) Maifeld A, Wild J, Karlsen TV, Rakova N, Wistorf E, Linz P, Jung R, Birukov A, Gimenez-Rivera VA, Wilck N, Bartolomaeus T, Dechend R, Kleinewietfeld M, Forslund SK, Krause A, Kokolakis G, Philipp S, Clausen BE, Brand A, Waisman A, Kurschus FC, Wegner J, Schultheis M, Luft FC, Boschmann M, Kelm M, Wiig H, Kuehne T, Müller DN, Karbach S, Markó L. Skin Sodium Accumulates in Psoriasis and Reflects Disease Severity. J Invest Dermatol. 2022 Jan;142(1):166-178.e8. doi: 10.1016/j.jid.2021.06.013. 

(9) Popova, T., Petrova, T., Karadzhov, S. and Krustanova, G., 2016. Investigation of the Biocidal effect of electrochemically activated aqueous sodium chloride solution on Staphylococcus aureus. Traditions and Modernity in Veterinary Medicine. Scientific Journal of the Faculty of Veterinary Medicine of University of Forestry, Sofia, 1(1), pp.67-72.

Abstract. Studies were carried out to determine the sensitivity of Staphylococcus aureus to electrochemically activated 3% aqueous sodium chloride solution (anolyte) in different concentrations – 100 %, 50 %, 25 % and 12.5 %. As a control was used the disinfectant Virkon S, applied at final concentrations of 1 %, 0.5 %, 0.25 % and 0.125 %. Two referent strains of S. aureus were used – ATCC and Kowan. It had been found that the anolyte in concentrations of 50 and 100 % inactivates the cells of S. aureus ATCC in suspension at a density of 106 cells/ml within 5 min. After 10 minutes of impact and lower concentrations (25 and 12.5 %) had a bactericidal effect. The anolyte in all tested concentration (12.5 to 100 %) had a bactericidal effect on the cells of S. aureus Kowan in suspension with concentration of 106 cells/ml in 10-minutes. Shorter intervals tested (2 min and 5min) were not sufficient for achieving bactericidal action even at a concentration of anolyte 50 and 100 %, while after 10 min and even smaller concentrations (25 and 12.5 %) had such action. S. aureus ATCC showed slightly higher sensitivity to anolyte and Virkon S compared to the other tested strain Kowan. The effect of the control disinfectant Virkon S on the tested staphylococcal strains was completely analogous to that of the anolyte.

(9) Olszewski WL, Moscicka M, Zolich D, Machowski Z. Human keratinocyte stem cells survive for months in sodium chloride and can be successfully transplanted. Transplant Proc. 2005 Jan-Feb;37(1):525-6. doi: 10.1016/j.transproceed.2004.12.174. 

Abstract. Human skin fragments can be preserved in anhydric sodium chloride at room temperature for periods of weeks or months and successfully transplanted, retaining normal morphological structure. Skin fragments of 10 x 10 x 6 mm were harvested during elective vascular and orthopedic surgery of lower limbs, dried of blood, and placed in anhydric sodium chloride powder in tightly sealed containers. Prior to transplantation to scid mice, the specimens were desalinated and rehydrated. Specimens preserved for 1-6 months and harvested 3-4 weeks after transplantation revealed intensive incorporation of bromdeoxyuridine (BdUR) into basal keratinocytes (stem cells). They expressed p63 and CD29 (stem cells and transient cells antigens), proliferating cell nuclear antigen (PCNA), and cytokeratin 16 specific for proliferating keratinocytes. We conclude that human epidermal stem cells can survive in a dehydrated state in sodium chloride for months and after transplantation give rise to keratinocyte progenies. Skin fibroblasts and some resident immune cells can also survive.