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Is Salt Good or Bad for Your Health? Exploring The Great Salt Debate

I've been collecting articles and research studies to build this blog post for a few months now and subsequently putting off writing it, until now... (there's a TLDR at the bottom of the blog)


Let's first define what salt even is... Salt is made up of sodium chloride AKA table salt. Salt is 40% sodium and 60% chloride. Sodium is commonly found in MSG, baking soda and as a preservative as sodium nitrate.


There is a cellular protein called the sodium-potassium pump that is present in every living cell in the human body and these pumps push sodium and potassium ions in and out of the cell to create something called 'action potentials.' These action potentials can also propel calcium ions across to elicit muscular contractions in both the heart and skeletal muscle as well digestive movements through the GI tract. Without adequate sodium and potassium, the body will have difficulty generating these action potentials, thus you can experience headaches, brain fog, low energy, muscle aches/cramps, and weakness to name a few symptoms.


Sodium and potassium are also important in regulating fluid balance in the body and thus overall total body hydration status. The less water we drink, the more salt we can retain and the more water we drink, the more salt (and other electrolytes) we will urinate out. Other important electrolytes to note are magnesium, calcium, chloride, phosphorous and bicarbonate.


Dehydration is defined as net water loss from the body and severe losses account for 5% of body water lost; but even 1% can be clinically relevant. Symptoms of dehydration includes thirst, dark urine, dry skin and cracked lips, headaches, moodiness, brain fog, fatigue, muscle cramps, constipation, nausea, dizziness, low blood pressure and rapid heartrate.


"It is well established that the quantity of salt required to maintain normal physiological homeostasis in adult humans is <1.25 g/d." But that doesn't account for increased physical activity, daily movement, job demands, social demands, current diet restrictions/limitations, etc. "Given that sodium ions are an essential noncaloric nutrient, there has been some controversy in the field concerning how large the reduction in salt intake should be."


Salt has been demonized for so long as it is connected to negative health outcomes including hypertension, kidney and liver disease, and increased risk for heart disease. The CDC states that Americans consume more than 3400mg of sodium per day on average which is above the national recommendation of less than 2300mg per day. If you have chronic kidney disease and/or diabetes you may even be recommended to drop your total sodium intake to less than 1500mg per day. One brand argues "Why aren’t we talking about the glut of sugary foods and the lack of exercise that permeate modern living? Because sodium is a convenient and easy-to-understand scapegoat. Because the government subsidizes the sugar industry to the tune of $4 billion per year. Because many don’t want to hear they need to exercise frequently."


For those that don't have chronic health concerns, sodium and water retention usually isn't an issue because our bodies will regulate those two things well but the CDC still recommends that people limit their sodium intake to 2300mg per day in order reduce their risk for cardiovascular issues. However, we can run into issues if we don't consume enough salt though. In the absence of adequate sodium intake, the body will stimulate blood pressure elevating hormones in an attempt to spare further sodium losses. So our blood pressure can actually increase without enough sodium! We can also be at a higher risk for poor bone density if our bodies have to pull electrolytes from bone to maintain balance.


On the other hand, salt has also been glamorized in the wellness space as an essential electrolyte that we aren't consuming enough of. So which is it? Do we need to limit it or do we need more of it? With any nutrition recommendation, IT DEPENDS on the individual. So let's review what the some of the research says and who it applies to.


 

Study 1: An old study from 1988 that looked at more than 10,000 men and women aged 20-59 years old, assessed the relationship between a 24-hour urinary electrolyte excretion and blood pressure. The study found that as an individual had a higher sodium urinary excretion, their systolic (p<0.001) and diastolic (p<0.05) blood pressure increased as well even when controlling for BMI and alcohol intake. Heavy alcohol intake, defined as more than 300mL/week (roughly 10oz or more),was also strongly related to blood pressure increases.

It can be inferred from this study that lower sodium intakes might have a positive effect on blood pressure especially in those with high BMIs and those who consume more than 10oz of alcohol per week.


Study 2: A newer study from 2018; a systemic review of 9 studies that looks at reducing salt intake for heart failure patients and its potential benefits. This study looked a 479 patients with heart failure to determine whether or not the evidence is there to support or invalidate reduced dietary sodium intake. Heart failure is a condition where the heart doesn't have enough strength to pump blood to the rest of the body. This can lead to fluid retention thus sodium retention and eventually a pericardial effusion, when fluid is surrounding the heart muscle impacting it's function further.

There was not sufficient data to draw a conclusion when looking at inpatients however, when looking at an outpatient population, heart failure was not improved by restriction of salt intake in 2 studies whereas 2 other studies showed significant improvement. This study did not provide adequate results to draw conclusions or recommendations from.


Study 3: Looked at fasting urinary sodium and potassium excretion (will not be addressing potassium excretion as this blog is looking at sodium) and the risk of cardiovascular events in patients with cardiovascular (CV) disease or diabetes (DM). This was an observational study with a follow up of 56 months that looked at 2 cohorts containing a total of 28,880 individuals.

The study found that a urinary sodium excretion of greater that 7 grams per day was associated with an increased risk of CV death and a sodium excretion of <3 grams per day was associated with an increased with of CV death and hospitalization for congestive heart failure.

To note, urinary sodium excretion is largely dependent on adequate kidney function, fluid intake, sodium intake and overall electrolyte balance within the body.

We can infer from this study that too high (7g) and too low (3g) urinary sodium excretion is associated with increased cardiovascular death and hospitalization for heart failure in those with a diagnosis of CV or DM.


Study 4: Done in 2018, looked at 2,632 normo-tensive (no hyper or hypotension) subjects ages 30-64 years old to answer the question of long-term effects of dietary sodium on blood pressure over a 16 year follow up.

The study found "After 16 years of follow-up, those with the lowest Systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels (129.5 and 75.6 mmHg, respectively) were those with higher intakes of both sodium and potassium while those with the highest SBP and DBP levels (135.4 and 79.0 mmHg, respectively) were those with lower intakes of both.

It was concluded that this study offers no support for lowering sodium intakes to recommendations of less than 2300mg/day among healthy individuals.


Study 5: Published in 2017 looking at the association between urinary sodium excretion, CVD and mortality in the elderly, 920 participants, aged 65 years or older. This was cohort study meaning researchers watched a group of individuals overtime who share common characteristics but nothing is controlled for.

The study found that high levels of sodium excretion in the urine was not associated with adverse outcomes in this elderly population and lower sodium excretion was associated with increased mortality especially among the more frail participants. . This means sodium restriction may not be helpful for the elderly population.


Study 6: Published in 2024, this study looked at effects of a salt substitute on incidence of hypertension and hypotension among normotensive adults. This study looked at 48 elderly care facilities in the Chinese population over 2 years and found that replacing usual salt with a substitute resulted in lower hypertension incidence and did not increase the incidence for hypotension. The mean blood pressure values did not increase from baseline in the salt substitute group but did for the usual salt group.

This study supports the use of salt substitutes to help reduce the incidence of hypertension in normo-tensive, elderly Chinese adults.


Article 7: published in 2023, this article states that cutting sodium below the current recommendations (2300mg/day) could be counterproductive in heart failure patients. While "the average American consumes over 3.4 grams of sodium per day" a meta-analysis found that "patients following a diet with a sodium intake target below 2.5 grams per day were 80% more likely to die than those following a diet with a target of 2.5 grams per day or more."

This study published in 2022 reviewed 17 randomized controlled trials with a total of 1705 individuals and found that sodium restriction did not reduce the risk of all-cause mortality, hospitalizations, or the composite of death/hospitalization in those with heart failure. There were 2 RCTs (accounting for 2/3 of the data) that showed improvement in NY Heart Association Class with sodium restriction.



Study 8: Published in 2023 looked at adding salt to food and it's impact of incidence of chronic kidney disease (CKD). This was a cohort study and people provided self-reported data of the frequency they added salt to foods. Participants were free from CKD at the beginning of the study. Those that added more salt to their foods were found to have a high BMI, be a current smoker, have diabetes or cardiovascular disease at baseline. Knowing this as well as the fact that it was self-reported data, makes me way less likely to utilize the outcomes of this study when educating patients and/or clients about salt intake.

The study did control for sex, age, race, ethnicity, BMI, Townsend Deprivation Index (includes unemployment status, non-car owners, homelessness, and other SES values), smoking, drinking, regular physical activity, high cholesterol, CVD, and diabetes at baseline, and found that "the association was attenuated but still significant for those who reported sometimes adding salt to food, those who reported usually adding salt to food, and those who reported always adding salt to food compared to those who reported never or rarely adding salt to food." The association was still the same even after controlling for hypertension, infectious disease, immune disease, and nephrotic drugs at baseline. What does this mean? That 'sometimes adding salt to food' may increase the risk of developing chronic kidney disease especially if you are already a diabetic, have CVD, or have a higher BMI.

This study highlights the important fact that having pre-existing comorbid conditions can lead to the individual being more sensitive to higher intakes of salt and worsening current conditions or developing other medical conditions.


Study 9: Published in 2012 and looked at dietary sodium intake with heart failure. "Interestingly, and paradoxically, the suggested 1500 mg daily sodium intake for the general population is less than the limit proposed for HF patients by most guidelines, which appears as a contradiction."

"Sodium reduction is difficult to adhere to even among patients with symptomatic HF, with an estimated compliance rate of only 33% as noted by 3-day food diaries."

The table below outlines fairly recent sodium restriction guidelines as recommended by certain organizations.



In animal studies, restricting sodium in the diet led to a decrease in cardiac output (heart function) and an increase in vascular resistance in turn activating the renin angiotensin aldosterone system, which can increase blood pressure and retain sodium (see photo below).

Providing a high sodium diet (2760mg/day) and a 1L fluid restriction didn't have a large impact on kidney function (when looking at serum CRE and BUN levels) and the reverse was true; that a low sodium diet was shown to increase kidney blood markers which is not favorable.

For the sake of this study, "sodium intake is classified into “very low” (230–800 mg/d), “low” (1610 mg/d to 2000 mg/d), and “moderate-to-high” (2300–5750 mg/d) dietary intake... Adverse event rates, defined as HF (heart failure) or non-HF readmission rates and mortality rates, were higher with low-sodium diets in several studies. Mortality rate was lower in the moderate-to-high sodium group in 3 studies in comparison with low-sodium diet." The study also found that restricted fluid intake may be in part responsible for differences in dietary sodium intakes and readmission rates.

In two observational studies, it was found that those with heart failure consuming more than 2800mg/day resulted in more HF hospitalizations in comparison to those consuming a lower intake. Those consuming more than 3g/day was associated with better symptomatic outcomes however, did result in creased readmissions and mortality.

To summarize, the 3 larger RCTs reviewed showed that lower sodium intake was associated with worse outcomes (increased mortality and readmissions) but was not free from bias. "Currently, there are insufficient data to endorse any specific level of sodium intake with certainty, and differences among the various HF subpopulations are not known... Physicians should consider some degree of sodium restriction in patients with stage C and D HF, but more data are needed to support a specific sodium intake level."


Study 10: Published in 2023, this review article looked at the role of dietary salt in metabolism and energy balance.



In regards to energy balance, high salt intake can promote production of ghrelin which in turn promotes increased food intake. High salt intake has also been shown to reduce levels of adiponectin and glucagon-like peptide 1 (GLP-1) which can lead to weight gain.

"The beneficial effects of sodium restriction on HF are thought to be achieved by reducing SBP and DBP, oxidative stress, arterial stiffness, inflammation, and aldosterone levels." however, some studies show that salt reduction can increase LDL levels, total cholesterol and triglycerides; exactly what we don't want for our heart health.

An observational study "demonstrated that sodium restriction (<2.5 g/d) in patients with HF was associated with an increased risk of death or hospitalization compared to those without a sodium-restricted diet." Low sodium intake has also been shown to worsen systemic inflammation in heart failure patients.

So it seems sodium intake of less than 2500mg can be detrimental to our heart health but too much can also impact our appetite and likely cause weight gain in the long run.


Study 11: a systematic Review and Meta-Analysis looking at how adherence to the DASH diet influences blood pressure. The study showed that the greater the adherence to the DASH diet recommendations, the greater the beneficial effects on blood pressure. and might also have a positive effect on overall heart health (looking at total and LDL cholesterol). The DASH (dietary approaches to stop hypertension) diet comprises of fruits, vegetables, whole foods, whole grains and low fat dairy products to assist with lower sodium intake overall. This study shows that consumption of less salt (not defined) can improve/lower blood pressure in those who adhere to the DASH diet.


Study 12: Published in 2018, looked at urinary sodium excretion first thing in the morning, blood pressure, CVD risk and mortality in over 168,000 individuals ages 35-70 who DID NOT have pre-existing cardiovascular disease. These people were following over a 3, 6, and 9 period.

The study concludes that "decreased sodium (less than 4g/day) intake was (significantly) associated with an increased CV risk and an increased sodium intake was associated with an increase in stroke." So it's seems that the middle ground of sodium intake at 4.43-5.08g/day was the more optimal range when it comes to optimizing blood pressure, CVD risk and mortality.


 

TLDR:

When it comes to patients with comorbid conditions: I believe there is some benefit to reducing sodium in the diet for those with how already have heart failure, diabetes, kidney and liver conditions UNLESS they eat a largely unprocessed diet (free from fried foods, prepackaged meals and preserved foods). But I believe that anything less than 2000mg is unhealthy for anyone with any condition (even less than 2300mg which is the CDC's recommendation). The studies also show that a sodium restriction may not be helpful for the elderly population. These people are likely not eating enough food as well as fluids so further restriction of sodium could also result in food restriction and electrolyte abnormalities which can be detrimental and even fatal for this population.


When it comes to generally healthy individuals: I believe that a sodium restriction is unnecessary but higher than 6000mg could be detrimental in regards to heart health, cardiovascular disease risk and even our waist lines if we experience increase hunger from higher intakes of sodium. Generally healthy individuals are those that don't eat in excess, exercise regularly and maintain a healthy weight for their demographic. These people eat in a 80-90/10-20 manner, meaning their diet is largely whole, unprocessed foods with adequate fluids and fiber and occasionally they eat less nutritious foods but that's not the majority of their diet. I believe that capping sodium intake to a maximum of 4-6g per day is beneficial.


When it comes to athletes: I believe that adding additional electrolytes (this includes sodium) can be beneficial based on training demands, amount of electrolytes lost during training and lifestyle, and how much sodium is already in the diet. I believe that capping sodium intake to a maximum of 4-6g per day is beneficial.


 

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