Abstract
Heart disease is a leading cause of mortality and morbidity globally. Sedentary lifestyle, bad eating habits, and little to no exercise have led to an alarming rise of lifestyle-mediated diseases in recent times. Table salt is one of the staples of all our kitchens and dining tables. Salt contains almost 98% sodium chloride. The unregulated amount of salt in our diet has led to adverse cardiovascular consequences. Fast foods such as salted French fries and Chinese cuisine may contain as much as 7,000 mg of sodium in a single meal! The American Heart Association (AHA) recommends a daily intake of not more than 2.3 g of salt per day (roughly one teaspoon). For patients with hypertension, heart failure, or kidney disease, a lower daily cut-off of 1.5 g of salt has been proposed but is still under debate. There is conflicting evidence of going too low with salt restriction as recent studies have shown increased adverse events when salt was restricted to beyond the recommended per-day threshold. The DASH (dietary approaches to stop hypertension) diet is a novel dietary pattern that is recommended for patients with hypertension. The DASH diet is not a restrictive or short-term diet but rather a sustainable and balanced approach to eating. It promotes a wide variety of foods, focusing on whole, unprocessed options, and encourages portion control. Adhering to a DASH eating pattern by itself can lower the systolic blood pressure by 6–11 mm Hg. Reducing salt intake can be challenging, as salt is present in many processed and packaged foods, restaurant meals, and fast food. More than 70% of the salt we eat, according to the AHA, comes from processed, prepackaged, and restaurant foods.
“Salt Lite” is often marketed as a healthier alternative for individuals looking to lower their sodium intake. It typically contains a blend of potassium chloride with sodium chloride and is hence not totally “sodium free.” Individuals considering the use of “Salt Lite” should be aware of its higher potassium content and should not use it if they have a kidney disease or are on drugs that can cause hyperkalemia. There is a common misconception that pink Himalayan salt is lower in sodium than regular table salt. However, both types consist of approximately 98% sodium chloride. Research has not shown that Himalayan salt has any unique health benefits compared to other dietary salts.
It is hence imperative for all individuals to restrict dietary salt intake to the recommended levels—as a measure toward a healthy lifestyle as well as a therapeutic modality for those with established cardiovascular diseases.
Introduction
Heart disease, including conditions such as hypertension and cardiovascular disorders, remains a leading cause of morbidity and mortality worldwide. Lifestyle modifications, including dietary changes, play a crucial role in the management and prevention of heart disease. One such dietary modification is the reduction of salt intake.
Our diet is one of the most crucial factors that directly or indirectly affects our health and well-being. The age old saying “You are what you eat” could not hold more relevance in this context. Living in a world that is just emerging out of the clutches of the deadly COVID-19 pandemic, diet has never been a greater risk factor toward the development of cardiovascular disease (CVD).
The pandemic ravaged many lives either directly or indirectly. Many lost their lives, their loved ones, their health, but it also changed our lives forever. Today, we find a sharp rise in the number of overweight and obese individuals compared to the pre-pandemic era. A quick survey of your own friends and family will reveal that almost a near majority of individuals have gained an excess of body weight. Unhealthy eating habits and access to fast foods via the rise of food delivery apps have invited obesity and its associated diseases into our lives—an unhealthy food habit is now just a few clicks away, delivered right to the doorstep. Fast foods such as salted French fries and Chinese cuisine may contain as much as 7,000 mg of sodium in a single meal! The unregulated amount of salt in our diet has led to adverse cardiovascular consequences. There has been an alarming rise in young hypertension, metabolic syndrome, sleep apnea, and premature coronary atherosclerosis.
Salt, or sodium chloride, is a commonly used seasoning and preservative in food. Table salt consists of about 40% sodium and 60% chloride. While sodium is an essential mineral required for various bodily functions, excessive intake can have detrimental effects on cardiovascular health. High salt intake has been linked to hypertension, which remains one of the most significant causes of premature morbidity and mortality worldwide. It also contributes to fluid retention, strain on the heart, and an increased risk of stroke.
The Burden of Salt
The American Heart Association (AHA) has provided guidelines for salt intake to promote heart health. The general recommendation for the general population is to consume no more than 2,300 mg of sodium per day, which is equivalent to approximately one teaspoon of salt. However, for individuals with heart disease or those at a high risk, such as those with hypertension, diabetes, or chronic kidney disease, the recommended sodium intake is even lower—around 1,500 mg per day.
The average Indian adult consumes around 11 g of salt per day, which is more than double the recommended intake of salt and is much greater than the physiological requirement of the body.
Multiple studies have demonstrated a consistent relationship between dietary salt intake and blood pressure. A 4.4 g reduction in daily dietary intake of salt decreases blood pressure by about 4.2/2.1 mm Hg. In cohort studies, a 5 g per day higher salt intake (2,000 mg of sodium) is associated with a 17% greater risk of total CVD and crucially a 23% greater risk of stroke.
Reducing salt intake can be challenging, as salt is present in many processed and packaged foods, restaurant meals, and fast food. More than 70% of the salt we eat, according to the AHA, comes from processed, prepackaged, and restaurant foods. It is important for patients with heart disease to be aware of hidden sources of sodium and to make conscious efforts to limit their intake.
It is crucial for patients with heart disease to work closely with their healthcare providers and registered dietitians to develop personalized dietary plans. These plans should consider individual health conditions, medications, and specific nutritional needs.1–6
The Dietary Approaches to Stop Hypertension Diet
The dietary approaches to stop hypertension (DASH) diet is a well-known eating plan that has been specifically designed to lower blood pressure and promote heart health. It emphasizes the consumption of nutrient-rich foods while limiting sodium intake, making it an excellent choice for individuals with hypertension. The DASH diet originated in the 1990s. In 1992, the National Institutes of Health (NIH) started funding several research projects to see if specific dietary interventions were useful in treating hypertension. Subjects included in the study were advised to follow just the dietary interventions and not include any other lifestyle modifications to avoid confounding factors. They found that only the dietary intervention alone could decrease systolic blood pressure by about 6–11 mm Hg. The effect on blood pressure reduction was seen both in normotensive and in hypertensive individuals. Based on these results, in some instances, DASH has been advocated as the first-line pharmacologic therapy along with lifestyle modification. 7
The key features of the DASH diet include:
High consumption of fruits and vegetables: The DASH diet encourages a significant intake of fruits and vegetables, which are rich in potassium, magnesium, and fiber. These nutrients have been linked to lower blood pressure levels. Whole grains: Whole grains, such as brown rice, whole wheat bread, and oatmeal, are included in the DASH diet. They provide essential nutrients and fiber while promoting satiety. Lean proteins: The diet emphasizes lean protein sources, such as poultry, fish, and legumes, instead of high-fat meats. This helps to reduce saturated fat and cholesterol intake while providing necessary protein. Low-fat dairy: The DASH diet incorporates low-fat or fat-free dairy products, such as milk, yogurt, and cheese. These are excellent sources of calcium and protein while being lower in saturated fat. Limited sodium intake: The DASH diet aims to reduce sodium consumption to help lower blood pressure. It encourages the use of herbs, spices, and other flavorings as alternatives to salt. Limited sweets and added sugars: The DASH diet suggests limiting the intake of sweets, sugary beverages, and foods with added sugars. These foods are often high in calories and low in nutritional value.
The DASH diet is not a restrictive or short-term diet but rather a sustainable and balanced approach to eating. It promotes a wide variety of foods, focusing on whole, unprocessed options and encourages portion control.
Sacks et al, in their study on the effects of reduced sodium and the DASH diet on blood pressure, found that as compared with the control diet, the DASH diet resulted in a significantly lower systolic blood pressure at every sodium level and in a significantly lower diastolic blood pressure at the high and intermediate sodium levels. The DASH diet had a greater effect on blood pressure at higher sodium levels than it did at lower levels of sodium (p < .001). 8
A meta-analysis by Fillippou et al published in 2020 showed that, compared with a control diet, the DASH diet reduced both systolic blood pressure (SBP) and diastolic blood pressure (DBP) (difference in means: −3.2 mm Hg; 95% CI: −4.2, −2.3 mm Hg; p < .001, and −2.5 mm Hg; 95% CI: −3.5, −1.5 mm Hg; p < .001, respectively). Hypertension status did not modify the effect on BP reduction. The DASH diet compared with a control diet reduced SBP levels to a higher extent in trials with sodium intake >2,400 mg/d than in trials with sodium intake ≤2,400 mg/d, whereas both SBP and DBP were reduced more in trials with mean age <50 years than in trials of older participants. The adoption of the DASH diet was accompanied by significant BP reduction in adults with and without hypertension, although higher daily sodium intake and younger age enhanced the BP-lowering effect of the intervention. 9
The blood pressure–lowering effect of the DASH diet seems to stem from its ability to cause natriuresis, which in turn exerts an influence on the renin–angiotensin–aldosterone system. This results in vascular and hormonal responses, which lead to a hypotensive effect. Sacks et al suggested that the BP-lowering effect of the DASH diet compared with the control diet was almost threefold higher for those at higher sodium intake than for those at lower sodium intake. The low dietary sodium probably countered the hypotensive effects of potassium, or probably, the high calcium or potassium content of the DASH diet countered the effects of low sodium.8–12
The DASH diet also plays a role in the prevention of chronic heart failure as well as its management. Prospective observational studies have shown individuals adhering to a DASH pattern of eating have lower rates of heart failure incidence in women and also have a lower prevalence of hospitalization from heart failure and death in men. 13
The DASH diet offers a well-rounded and evidence-based approach to managing hypertension. By adopting the principles of the DASH diet and making healthy food choices, individuals with hypertension can take proactive steps toward improving their cardiovascular health and overall well-being.
Effects on Salt on Cardiovascular Physiology6, 14
The relationship between salt intake and CVD, particularly hypertension (high blood pressure), is well established. Excessive salt intake has been consistently associated with an increased risk of developing CVD, including heart disease, stroke, and other related conditions. Some of the effects of sodium on the cardiovascular system are as follows:
Left ventricular hypertrophy (LVH): LVH is an important risk factor for premature CVD. Salt intake, independent of blood pressure, was found to be an independent predictor of LV mass and a reduction in salt intake led to a regression of LVH. Blood pressure regulation: Sodium, the primary component of salt, plays a crucial role in fluid balance and blood pressure regulation in the body. When sodium intake is high, the body retains more water, which increases blood volume and puts additional strain on the blood vessels, leading to elevated blood pressure. Hypertension: High blood pressure is a major risk factor for CVD. Research indicates a strong connection between excessive salt consumption and the development of hypertension. Studies have shown that reducing salt intake can help lower blood pressure levels, both in individuals with hypertension and in those with normal blood pressure. Endothelial dysfunction: Excessive salt intake can contribute to endothelial dysfunction, which refers to the impaired function of the inner lining of blood vessels. Endothelial dysfunction has been recognized as a precursor to and predictor of later CVD in individuals with various cardiovascular risk factors. Studies have revealed that a key pathogenic mechanism of dietary salt (independent of its effect on blood pressure) is a profound reduction in vascular nitric oxide (NO) bioavailability that limits endothelium-dependent dilation. This reduction in NO is strongly associated with increased levels of reactive oxygen species (ROS) generated by NAD(P)H oxidase, xanthine oxidase, or uncoupled endothelial NO synthase within the vascular wall, leading not only to scavenging of NO but also to disruption of some signaling pathways that mediate its production.
14
Vascular stiffness: High salt intake has been linked to increased arterial stiffness, meaning that the blood vessels lose their ability to dilate and contract effectively. This stiffness can contribute to elevated blood pressure and further cardiovascular complications. Fluid retention and edema: Salt is one of the major substrates contributing to total body fluid balance. High salt intake triggers thirst, and the consequent increase in fluid intake leads to fluid retention in the intravascular compartment, leading to a rise in total blood volume. The kidneys and the heart are the main organs to compensate for these changes through hormonal responses (renin angiotensin aldosterone system/atrial natriuretic peptide), increased forward flow, cardiac output, and renal clearance. Dysregulations of these homeostatic mechanisms lead to fluid retention that is often triggered by increased intake of dietary salt and can be ameliorated by a reduction in salt intake. Salt sensitivity: It is important to note that individuals vary in their sensitivity to the effects of salt. Some people may be more prone to experiencing increases in blood pressure in response to high salt intake, while others may be less sensitive. However, even individuals considered salt resistant can still benefit from reducing salt intake for overall cardiovascular health.
Adverse Effects of Going Too Low
While a low salt diet is recommended for individuals with hypertension or CVD, it is important to note that extreme or excessively restrictive low salt diets can have potential negative effects on heart health such as the following:
Electrolyte imbalance: Sodium is one of the essential electrolytes in the body, and it plays a crucial role in maintaining fluid balance, nerve function, and muscle contractions, including those of the heart. Severely restricting sodium intake without proper monitoring can lead to an electrolyte imbalance, which may have adverse effects on heart rhythm and overall cardiac function. Orthostatic hypotension: Sodium helps regulate blood pressure, and a drastic reduction in salt intake can cause a drop in blood pressure, leading to orthostatic hypotension. This condition is characterized by dizziness or light-headedness upon standing up and can increase the risk of falls and other related complications, particularly in older individuals. Adverse effects on kidneys: Sodium balance is intricately linked to kidney function. In certain individuals, extremely low salt intake may negatively impact kidney function and disrupt the delicate balance of electrolytes, potentially leading to kidney problems or impairing the body’s ability to excrete waste effectively. Insufficient micronutrient intake: Restricting salt intake to an extreme level may also result in inadequate intake of certain essential nutrients, such as iodine. Iodized salt is a common source of dietary iodine, and a deficiency in this mineral can have implications for thyroid health and overall cardiovascular well-being. Adherence challenges: Maintaining a very low salt diet can be challenging for some individuals due to the prevalence of salt in processed foods, restaurant meals, and convenience foods. Strictly adhering to an extremely low salt diet may lead to feelings of deprivation, which can make it difficult to sustain in the long term.
Salt and Heart Failure
A diet high in sodium is associated with an increased risk of cardiovascular comorbidities, especially hypertension and heart failure (HF). The prevalence of HF is rising all over the world, and in India, it is 1.2 per 1,000 population as per the UK–India Education and Research Initiative Study. 15 An imbalance involving the renin angiotensin aldosterone system (RAAS) is the key pathogenic mechanism in the incidence or worsening of HF in patients consuming a high sodium diet. Imbalance of the RAAS system leads to sodium and water retention, leading to fluid overload manifesting as peripheral and pulmonary edema. An increase of 5 g salt a day leads to an extracellular volume expansion by almost 1.5 L, which leads to cardiac decompensation and HF. Excess salt is harmful both to patients suffering with HF with reduced EF (HFrEF) and to those with HF with preserved EF (HFpEF), though most of the data of benefit of salt restriction is with patients having HFrEF. Most studies on salt restriction have excluded patients with HFpEF. Dietary sodium retention is hence a mainstay in the management of HF. Patients with HF who actively adhere to a salt restricted diet benefit from a decrease in pulmonary capillary wedge pressure, decrease in extracellular fluid volume, decrease in arterial stiffness and systemic vascular resistance, suppression of oxidative stress and a decrease in aldosterone synthesis and its associated effects. 15
A pilot trial, SODIUM HF (Study of Dietary Intervention under 100 mmol in HF), compared a low sodium (1.5 g/day) diet with a moderate sodium (2.3g/day) diet in HF patients. At six months’ follow-up, on the basis of a post hoc analysis based on the dietary sodium intake achieved (> or ≤ 1,500 mg/d) in all patients, the authors observed that there was a significant association between a sodium intake of ≤1,500 mg/d and improvement in BNP levels and quality of life. 16
Another pilot study by Kalogeropoulos et al, the PROHIBIT (Prevent Adverse Outcomes in Heart Failure by Limiting Sodium) study, compared the effects of a 1,500 mg/day versus a 3,000 mg/day sodium diet in HF patients. The authors observed that while both meals were tolerated well by the participants, there was a significant improvement in the quality of life in the group restricting sodium intake to 1,500 mg/day but not in the 3,000 mg/day group. However, there was no significant difference in in the NTproBNP levels between groups. There was a significant reduction in the serum creatinine level in the 1,500 mg/day group. 17
Is Lower Always Better?
A recent article in the Journal of the American College of Cardiology (JACC) 18 discussed the results of a meta-analysis by Palicherla et al, 19 in which the authors after a meta-analysis of nine studies including 3,499 patients observed that as compared to usual dietary recommended sodium restriction, the group of patients who restricted sodium to lesser than the usual recommendation levels, showed a significant increase in in-hospital mortality, while there was no significant difference in hospitalization between the groups following dietary sodium restriction versus the usual low sodium diet. In the study, researchers analyzed nine randomized controlled trials that assessed different levels of sodium restriction for people with HF and included data on rates of death and hospitalization. Most of the studies were conducted between 2008 and 2022, except for one earlier study published in 1991. Together the trials enrolled nearly 3,500 HF patients in total.
Analyzing outcomes across all studies, the researchers found that patients following a diet with a sodium intake target below 2.5 g per day were 80% more likely to die than those following a diet with a target of 2.5 g per day or more. The sodium limits varied from about 1.2 to 1.8 g per day in the more restrictive study arms. The analysis did not show a trend toward increased hospitalizations among patients following more restrictive diets. 18 Hence, lower is not always better. It is prudent to remember here that sodium is an essential mineral responsible for many homeostatic processes in the body, as a result going too low or cutting out all the sodium from diet can have serious adverse effects as revealed by this meta-analysis.
Acute Decompensated Heart Failure
Restriction of sodium in patients admitted with acute decompensated HF (ADHF) is not necessary and can be counterproductive. Aliti et al studied the role of sodium restriction, which showed no effect on weight loss or clinical stability at three days, and they concluded that sodium restriction in patients admitted for ADHF is unnecessary. 20 In a large Italian study of patients admitted with HF, patients assigned to low sodium intake (1.84 g/day) compared to moderate sodium intake (2.76 g/day) had reduced diuresis, more HF readmissions, and a trend toward increased mortality. 21
Sodium Restriction in HFpEF
HFpEF accounts for almost half of all the cases of HF worldwide. While most large studies of salt restriction in HF have excluded the HFpEF subset, it is prudent to analyze the data available and make an informed assumption. Patients with HFpEF do indeed have a different response to the standard therapies of HF—except SGLT2 inhibitors, which have shown mortality and HF reduction, and spironolactone, which has shown reduction in hospitalization, most of the other optimal therapies for HFrEF have drawn a blank in HFpEF. By virtue of its effect on fluid retention, salt restriction should play a role in response to therapy of patients with HFpEF. However, contrary to expectation, a recent study in patients with HFpEF revealed that an exaggerated dietary salt restriction could harm patients with HFpEF and is associated with a worse prognosis. 22 Machado et al also found that aggressive salt/water restriction does not provide clinical benefits in patients with HFpEF. 23
A lack of uniformity in limiting the amount of sodium restriction per day, unclear data on the associated use of fluid restriction, and simultaneous usage of diuretics and neurohormonal blockade agents as well as heterogeneity of the HF population studied could provide an explanation for the conflicting evidence in the HFpEF subset.
“Lite” Salt and Salt Substitutes: Hype or Hope?
“Salt Lite” is a term used to describe a type of salt that has a reduced sodium content compared to regular table salt. It is often marketed as a healthier alternative for individuals looking to lower their sodium intake or manage conditions such as hypertension or CVD.
Salt Lite typically contains a blend of sodium chloride (regular salt) and potassium chloride. Potassium chloride is used as a substitute for some of the sodium chloride to reduce the overall sodium content. Potassium is an essential mineral that helps regulate blood pressure and balance fluids in the body.
The primary purpose of Salt Lite is to provide a similar taste to regular salt while reducing the sodium content. However, it is important to note that while Salt Lite may be lower in sodium, it is not sodium free. It is still essential to use it in moderation and follow dietary guidelines recommended by healthcare professionals. Individuals considering using Salt Lite should be aware that it may have a slightly different taste compared to regular salt. Some people may notice a slight metallic or bitter taste due to the potassium chloride. It is advisable to try it in small amounts and gradually adjust to the taste if needed.
Potassium is an essential mineral that can help lower blood pressure. However, individuals with certain medical conditions, such as kidney disease or those taking certain medications, may need to limit their potassium intake.
The Salt Substitute and Stroke Study (SSaSS) was the largest clinical trial of salt reduction in cardiovascular events that evaluated the effect of replacing regular salt with salt substitute during cooking in Chinese participants. This study showed a reduction in the risk of stroke, major cardiovascular events, and all-cause mortality in the study group using a salt substitute compared to those using regular salt. 24
Pink Salt: A Healthier Salt? No!
Pink Himalayan salt is chemically similar to table salt. It is a rock salt (halite) that is mined from the Punjab region of Pakistan. There is a common misconception that pink Himalayan salt is lower in sodium than regular table salt. However, both types consist of approximately 98% sodium chloride. The rest of pink salt consists of trace minerals, such as potassium, magnesium, and calcium. These give the salt its light pink tint and also explain why it tastes different from regular table salt. Himalayan salt carries the same risks as any other type of dietary sodium. Research has not shown that Himalayan salt has any unique health benefits compared to other dietary salt. The mineral impurities that give it a pink color, often promoted as healthful, are far too low in concentration to help with nutrition. One would have to eat a lethal amount of sodium to achieve helpful quantities of the other minerals! Hence, consuming pink salt with the notion that it is “healthy” can have disastrous consequences.
“Table Salt” and Its Effect on Cardiovascular Health
Despite having added salt in food while cooking, many individuals prefer adding salt “on-table” to cooked food. There has been a lot of interest in understanding if the frequency of adding salt to food has a direct implication on CVD events or subtypes. The frequency of adding salt to food may be considered a surrogate marker for long-term sodium intake.
In a recent study by Ma et al evaluating the relationship between frequency of adding salt to foods and CVD risk, the authors found that during a median follow-up of 11.8 years, lower frequency of adding salt to foods was significantly related to lower risks of total CVD events after adjusting for covariates and DASH diet. Compared to the group that always added table salt to foods, the group that never/rarely added table salt to foods was related to a 23%, 26%, and 37% lower risk of total CVD events, ischemic heart disease, and HF, respectively. Among the CVD subtypes, the strongest association was found between the risk of HF and lower frequency of salt intake, followed by a lower risk of ischemic heart disease. With relation to the DASH diet, participants with the lowest salt intake with highest adherence to the DASH diet had the lowest risk of total CVD events. 25 This study corroborates the findings of a previous study 26 which also reported that a higher frequency of adding salt to food was associated with a higher risk of all-cause premature mortality and lower life expectancy. A recent trial 27 has also demonstrated a significant reduction in NtproBNP levels with dietary sodium reduction—a finding that reiterates that the greatest effect of salt restriction is on reduction of HF events. A strong relationship between the risk of ischemic heart disease and salt intake was also reported in a study from the Million Veteran Program. 28
Conclusion
Excessive sodium intake by virtue of its propensity to retain water has been associated with an increase in blood pressure. Hypertension, a silent killer, is often the result of a disregard for salt restriction in diet. Hypertension contributes to an increased risk of other types of heart disease, stroke, or renal failure. Excessive sodium intake and uncontrolled blood pressure are major risk factors both for the development of HF and for episodes of decompensation in those with chronic HF. A low-sodium diet may help lower or prevent high blood pressure and may reduce the risk of CVD. Sodium-rich diets are also usually high in total fat and calories, which contribute to obesity and its myriad complications. A link between sodium intake and osteoporosis and stomach cancer has also been proposed. Salt begets salt! The more you eat a salty diet, the more your tase buds will crave a salty diet; hence, it is imperative to cut down on salt intake at the very roots.
Some practical tips to achieve a low-salt diet are as follows:
Read food labels to identify the sodium content of packaged foods. Choose products labeled as low sodium or reduced sodium. Preparing meals at home gives you control over the ingredients and allows you to use less salt. Experiment with herbs, spices, and other flavorings to enhance the taste of your dishes. Limit processed foods, which often contain high levels of sodium. Be mindful of condiments such as soy sauce, ketchup, and salad dressings, which are high in sodium. Look for low-sodium alternatives or use them sparingly. Choose fresh herbs and spices to add flavor to your meals without relying on salt. Reduce eating out as restaurant meals are often high in sodium. When dining out, request for your food to be prepared with minimal salt and ask for sauces and dressings to be served on the side. Be a smart shopper create a shopping list in advance to avoid impulse purchases of high-sodium foods. Focus on fresh produce, lean proteins, and whole grains.
Footnotes
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
