"The salt of the earth." "Worth one's salt." "Salt away" savings. These age-old expressions illustrate the value humans have placed on salt for eons.
More recently, however, salt has gone from something treasured to something feared. Health authorities have been encouraging us for more than two decades to cut back on this once-prized substance, especially for lowering blood pressure and decreasing heart disease risk.
But are low-sodium diets necessary - or even safe - for everyone? Read on to learn more about salt and how much of it we should be eating, based on the best current evidence.
1. What is salt?
When you hear the word "salt," you probably picture a typical salt shaker filled with the white, crystalline substance that's added to food for seasoning purposes. Originating from seawater, evaporated lakes, or mines deep beneath the earth, salt not only brings out flavors in foods, it's also used as a preservative and plays an important role in curing, smoking, pickling, and processing food.
For centuries, salt was a precious commodity that was traded for gold. In fact, the term "salary" comes from salarium, the Latin word for salt.
Salt vs. sodium: What's the difference?
Although frequently used interchangeably, salt and sodium aren't the same thing - an important distinction when discussing daily intake. Sodium is a mineral that is found naturally in small amounts in many foods such as meat, milk, yogurt, certain tropical fruits, and vegetables like artichokes, celery, beets, and seaweed.
Salt is actually sodium combined with chloride, another mineral. Since sodium chloride is roughly 40% sodium, 5 grams of salt (about 1 teaspoon) contains about 2 grams of sodium. We get 90% of our sodium from salt that's added to processed foods. Some sodium also comes from baking soda (sodium bicarbonate) in baked goods, crackers and cookies.
In short, sodium is the essential mineral our body uses, but salt (sodium chloride) is the dominant way we take that mineral in.
Different types of salt
Salt is found on every continent, and edible forms are available in dozens of varieties. Here are a few of the most popular:
- Table salt: Known as rock salt, or halite, it is mined from underground deposits resulting from the evaporation of ancient seas. Rock salt can be used for curing meat or pulverized to a fine texture to create table salt. To prevent goiter and other problems caused by iodine deficiency, manufacturers typically add iodine and label their salt as iodized.
- Sea salt: Coarser-grained, flakier, and more subtly flavored than table salt, sea salt comes from evaporated present-day seawater. It may sometimes contain natural traces of iodine.
- Himalayan salt: Harvested from salt caves in the Himalayan mountains of Pakistan, this colorful salt ranges from off-white to deep pink and contains miniscule amounts of trace minerals despite common claims for larger amounts.
- Kosher salt: Its large size and coarse texture is used in the koshering process to draw fluids out of meat. Never iodized.
Although some forms are less processed than others and differ slightly in taste and trace mineral content, from a nutritional point of view, salt is salt, or sodium chloride (NaCl). Most salt substitutes are a mix of sodium chloride and potassium chloride (KCL).
2. Why do we need salt?
Sodium is an essential nutrient that must come from your diet because your body can't make it on its own. As the most concentrated electrolyte in your blood, sodium helps:
- maintain the delicate chemical and fluid balance in and around your cells
- maintain blood pressure
- contract muscles
- conduct nerve impulses
Sodium in your body is tightly regulated by your kidneys, central nervous system, and adrenal glands. When blood sodium levels rise too high, your brain responds by making you thirsty, prompting you to drink more water so the excess sodium can be excreted in urine.
If you eat too little salt, your adrenal glands release more aldosterone, a hormone that prompts your kidneys to retain sodium. However, this can have adverse effects on other hormones and potassium levels as your body makes adjustments in order to stay balanced and stable at all times. The sodium your body loses through urine and sweat must be replaced. This amount can vary considerably from day-to-day depending on weather, the intensity and duration of any physical activity performed, how much water you have consumed, your overall state of health, and other factors.
Indeed, drinking too much water without replacing lost sodium can have devastating consequences. Hyponatremia is an extremely dangerous condition in which there is too little sodium in the bloodstream. Symptoms of hyponatremia include headache, weakness, vertigo, muscle spasms, nausea and vomiting. Although it's often triggered by certain medications or an underlying illness, hyponatremia can also occur due to overhydration ("water intoxication") and inadequate sodium repletion during exercise, especially in hot weather, or in elderly adults who consume low-sodium, restrictive diets.
3.The controversy over salt intake
What is a "healthy" daily sodium intake? It seems like a simple question, yet it's one that's generated quite a bit of controversy over the past several decades.
According to major health organizations in the US and Europe, nearly all of us consume too much sodium on a regular basis, mainly from processed foods. They recommend that we sharply reduce our sodium consumption in order to prevent high blood pressure and decrease the risk of heart disease and kidney disease, down to the equivalent of just 1 teaspoon a day.
More on current salt recommendations....For instance, the 2015-2020 Dietary Guidelines for Americans specify that people should eat no more than 2.3 grams (2,300 mg) of sodium per day - the equivalent of about 1 teaspoon.
The American Heart Association goes even further, saying that everyone should ideally consume less than 1,500 mg of sodium (approximately ¾ of a teaspoon) daily. Most people would consume that much by just eating a bowl of soup or a Caesar salad.
The World Health Organization (WHO) recommends that we cap our salt intake at 5 grams of salt per day, which at first glance seems quite a bit higher than the amounts above. However, remember that salt is only 40% sodium. Therefore, the WHO's guidelines actually call for limiting sodium to 2,000 mg per day.
However, these recommendations have been publicly criticized by several researchers and physicians with expertise in the field of nutrition.
For instance, James DiNicolantonio, PharmD, has published articles saying our evolutionary need for salt is clear and suggesting that reducing salt consumption is unwarranted. He's also written a book called The Salt Fix, in which he discusses the potential risks to cellular processes and future chronic disease by consuming less than 3,000 mg of sodium per day.
Ketogenic diet expert Stephen Phinney, MD, stated in a recent Virta Health blog post: "[S]odium restriction as a national policy is increasingly apparent as a house built on sand."
Other experts have also been saying that too-low sodium intake may have unintended adverse health consequences.
4.Research on salt intake in healthy adults
Is there any evidence that following a low-sodium diet, when healthy, can help decrease your risk of developing future chronic disease? The answer may surprise you.
Systematic reviews and meta-analyses of randomized controlled trials (RCTs) - considered the strongest type of evidence - haven't found that sodium restriction reduces heart disease risk in healthy people with normal blood pressure. Observational studies, a lower level of evidence, show no evidence that higher sodium intake increases the risk of future cardiovascular disease in those currently without the disease.
Could limiting salt actually harm healthy individuals? One group of researchers who conducted a review of both observational studies and RCTs concluded that sodium restriction has no detrimental effects in healthy people and could potentially benefit some people. Therefore, they feel a low-salt diet is advisable for all.
However, this finding was contradicted by the recent PURE study, which extensively reviewed data on sodium intake from over 100,000 people living in 17 countries. In looking at the relationship between health habits and disease risk, researchers in the PURE study found that although consuming more than 7,000 mg of sodium per day was associated with increased risk of heart attack and death in people with hypertension (sustained elevated blood pressure), getting less than 3,000 mg of sodium per day was also linked to an increased CVD risk in both people with hypertension and those with normal blood pressure.
In earlier analyses by the same researchers consuming between 3 and 6 grams of sodium daily was linked to the lowest risk of heart disease and early death.
While observational data like this cannot prove that sodium intake is either a risk factor or a protective factor for heart disease it does suggest that diets with 3 to 6 gram of salt a day could be part of a healthy lifestyle. For more discussion about this, listen to cardiologist Dr. Bret Scher discuss the PURE study findings with its principal investigator Professor Andrew Mente.
Other experts have suggested that blanket low-sodium recommendations may have unintended health consequences in many people.This includes increased insulin resistance, which has been shown in several salt restriction trials in healthy adults. As discussed previously, sodium restriction signals the adrenal glands to release aldosterone, prompting the kidneys to hold on to sodium. Researchers have suggested that these higher aldosterone levels coupled with release of the stress hormone noradrenaline may be responsible for decreased insulin sensitivity in people who follow low-salt diets.
In 2017, a coalition of three European health organizations recommended an upper limit of 5,000 mg of sodium per day for most people - more than twice as much as the 2,300 mg guidelines that come from other major health organizations.
5. People on keto or low-carb diets may need additional salt
As we've noted in other posts on Diet Doctor, when you follow a low-carb or keto diet, your sodium needs increase - especially initially - as a result of changes in the way your kidneys handle sodium.
With decreased carb intake, insulin levels fall significantly. It's been known for decades that when insulin levels drop, the kidneys excrete more sodium and water, although the exact mechanism isn't clear.
If sodium isn't replaced, you're likely to develop the unpleasant symptoms of "keto flu," which include headache, fatigue, and weakness.
What's more, a keto or low-carb diet composed of mainly whole foods doesn't have a lot of sodium to begin with, especially compared to processed foods. Feel free to consume more salt.
Ways to increase salt intake - more info
Consuming about 4,000 to 7,000 milligrams of sodium (about 2 to 3 teaspoons of salt) is usually sufficient to get through keto-adaptation and can often be maintained beyond the transition period, depending on individual needs.
Here are a few ways to boost sodium intake. However, if you have elevated blood pressure, kidney disease or congestive heart failure, talk to your doctor first before increasing your sodium intake, especially if you take medication.
- Drink 1 or more cups of salty broth every day
- Add 1-2 teaspoons of salt in daily food preparation or at the table
- Eat olives, pickles, sauerkraut, and other salty keto foods regularly
- Choose standard rather than "low-sodium" sauces and seasonings for cooking
- Shake salt into a glass of water a couple of times a day.
6. What about salt intake in people with medical conditions?
So it appears that healthy people may not gain any health benefits by following salt-restricted diets. Surely there must be good research supporting the low sodium recommendations for people with chronic disease?
In truth, much of the evidence has been contradictory or inconclusive.
And note: all of the research on sodium's effects has been conducted in people eating standard American diets or low-fat diets rather than low-carb or ketogenic diets. That means most of the salt likely came from processed high carbohydrate food, not from real foods like meats and vegetables with added sea salt. No high-quality evidence exists that compares salt restriction on its own to carb restriction for improvements in health conditions.
And we do know that high-quality evidence has repeatedly demonstrated that low-carb and ketogenic diets - without salt restriction - can help reduce elevated blood pressure, waist circumference, and high blood sugar and insulin levels. In short, growing evidence says restrict the sugar and carbs, not the salt, if you want to really improve your chronic conditions.
Let's take a closer look at the mostly weak research evidence for salt restriction as it relates to common chronic diseases:
Hypertension
Hypertension is the medical term for high blood pressure. It currently affects one in three people and is especially common in older, overweight or obese individuals.
Everyone's blood pressure increases during physical activity and stressful situations. This is normal and poses no harm as long as blood pressure quickly returns to a healthy range. However, blood pressure that remains elevated throughout the day can damage your arteries and increase the risk of heart attack, stroke, kidney disease, loss of vision, and other serious medical problems.
People with hypertension are usually put on medication and advised to minimize salt intake based on several old studies suggesting that higher sodium intake may raise blood pressure.
Is there overwhelming evidence that salt restriction lowers blood pressure? No, not really, for a number of reasons:
- Not everyone is salt sensitive. First off, consuming a lot of sodium doesn't raise blood pressure in everyone, including those with hypertension. A person whose blood pressure increases after eating salt is said to have "salt-sensitive hypertension" due to a combination of genetic and environmental influences on the complex systems that regulate the body's sodium balance. It's estimated that about 50% of those with hypertension and 25% of individuals with normal baseline blood pressure are salt sensitive, meaning their blood pressure increases by at least 5 points when following a high-sodium diet compared to a low-sodium diet.Therefore, about half of all people with hypertension do not respond to higher sodium intake with a significant rise in blood pressure and do not respond, as discussed next, with lower blood pressure to lowering salt intake.
- Reducing sodium intake only slightly decreases blood pressure. Systematic reviews and meta-analysis of trials have found that for most hypertensive adults, sodium restriction doesn't lead to a dramatic decrease in blood pressure. In practical terms, going from 3,500 mg to 1,500 mg of sodium per day might reduce blood pressure by an average of 5 points. Although this modest change may be viewed as a statistically significant reduction in risk by researchers, most people would likely find it not very rewarding as a result, when such severe sodium restriction is very difficult to do and nearly impossible to sustain long term.
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Sodium restriction may have adverse effects. Furthermore, cutting back on salt may have a negative impact on other health markers in hypertensive adults. In a very large review of 185 clinical studies, people with hypertension who followed a sodium-restricted diet for two or more weeks experienced a 3.5% decrease in blood pressure, on average.
However, this came at the expense of an increase in triglycerides and in the adrenal hormones aldosterone, adrenaline and noradrenaline, which could potentially lead to health problems over time. Noting the study's short time frame the authors concluded: "we do not know if low-salt diets improve or worsen health outcomes." What's more, the response to sodium restriction in hypertensive individuals seems to include increased insulin resistance, regardless of whether they are salt sensitive or not. Thus, rather than simply measuring small changes in blood pressure, what we really need to know is if long-term health outcomes improve or not. Unfortunately, we don't have that data.
- Overall diet may affect blood pressure more than salt does. Other researchers have suggested that rather than restricting sodium intake, those who are salt sensitive should be provided with tools to improve the quality of their diet, promote weight loss and decrease insulin resistance, which could help make them less salt sensitive and reduce their disease risk. A very-low-carbohydrate, ketogenic diet often significantly decreases blood pressure in those who are overweight or have metabolic syndrome regardless of sodium content.
Heart disease
Heart disease, also known as cardiovascular disease (CVD), is a broad term that includes several disorders. People with CVD are generally advised to reduce their salt consumption as part of a "heart healthy diet," but here is what the research evidence actually has found:
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Atherosclerosis: The most common type of cardiovascular disease is coronary artery disease due to atherosclerosis, a process in which plaque builds up in the walls of the arteries, restricts blood flow, and increases heart attack risk.
A recent systematic review and meta-analysis of 11 randomized controlled trials (RCTs) concluded that reducing sodium by an average of 3,000 mg per day improved arterial elasticity in people with hypertension, heart disease, diabetes, obesity, or no health issues.However, with the exception of one study in 169 hypertensive individuals, the studies were fairly small (between 6 and 40 participants), lasted only one to six weeks, and provided no data on clinical outcomes such as heart attacks and strokes. Therefore, the long-term effects of sodium restriction on arterial health are yet to be determined. By contrast, several large observational studies have found that very low sodium intake is associated with worse cardiovascular outcomes.
While this is associational data, the study authors hypothesize that it is due to the hormonal alterations in aldosterone and adrenaline discussed previously.
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Congestive heart failure: In congestive heart failure (CHF), another common disorder, the heart's ability to pump blood is impaired, leading to fluid buildup in the lungs and extremities. Individuals with CHF are usually told to minimize sodium intake in order to prevent fluid overload.
However, no strong research evidence exists suggesting that severe sodium restriction is the best strategy for CHF.Indeed, some in the medical community are rethinking whether patients with CHF benefit from very-low-sodium diets.
In 2018, researchers performed a systematic review and analysis of nine RCTs and concluded that a lack of high-quality evidence exists in support of current low-sodium guidelines for CHF.
Based on the inconsistent results across the studies, it's possible that some people may be more sensitive to sodium's fluid-retaining effects than others. Although more research is needed, individualized sodium recommendations may be most appropriate for managing CHF.
Diabetes and prediabetes
At increased risk for both heart and kidney disease, people with diabetes usually receive advice to limit their salt intake. At one time, the American Diabetes Association recommended that individuals with diabetes aim for less than 1,500 mg of sodium per day; however, this was modified to 2,300 mg per day in the 2019 Standards of Care in Diabetes based on the lack of evidence supporting a further restriction.
Overall, the evidence to date seems to suggest that salt restriction doesn't improve diabetes outcomes.
In short, while avoiding very high sodium intakes greater than 6 grams a day may be beneficial for people with diabetes who have salt-sensitive hypertension, severe sodium restriction in everyone else with diabetes might end up doing more harm than good.
Kidney disease
When functioning properly, your kidneys reabsorb water, sodium and other nutrients from your blood as needed and excrete whatever isn't needed into your urine.
In chronic kidney disease, the kidneys become less efficient at eliminating excess sodium from the body. Additionally, hypertension is a leading cause of kidney failure because increased blood pressure can damage the delicate arteries that lead to the kidneys. For these reasons, the National Kidney Foundation advises people with kidney disease to limit their sodium intake to less than 2,000 mg per day.
A recent systematic review and analysis of RCTs found that sodium restriction in people with early to end-stage kidney disease can significantly lower blood pressure and reduce urinary albumin. Albumin is a protein normally present in blood, and its appearance in urine indicates that the kidneys aren't functioning the way they should be.
However, the optimal sodium restriction for people with chronic kidney disease isn't clear. A controlled 4-week study found that the benefits of reducing salt were most pronounced in hypertensive people with kidney disease whose usual diets provided 5,700 mg of sodium per day. And an observational study found that consuming more than 4,500 mg of sodium daily was associated with increased risk of CVD, heart attack, and stroke in people with chronic kidney disease. However, a wide range of sodium intakes below this level were all linked to lower risk. Therefore, for this group, moderate sodium restriction may be beneficial and easier to sustain than extremely low salt intake. Unfortunately, these studies did not adequately control for the quality of food intake, thus leaving some questions about the applicability to a real-foods, low-carb diet.
7. Is salt the real culprit?
According to health organizations, it is the high amounts of sodium in processed foods that have played a major role in the epidemics of heart disease, diabetes, and other cardiometablic conditions. However, what if it isn't the sodium but rather the sugar and refined carbs that are responsible for most or all of the effects of processed food?
Some researchers have suggested that sugar rather than sodium is the driving force in hypertension, while others say that it's actually a combination of sugar and salt. However, most studies have a hard time separating overall salt intake from consumption of these unhealthy, high-carbohydrate processed foods.
We know that reducing carbs can dramatically lower blood pressure, decrease CVD markers, help reverse diabetes, and promote weight loss - even with moderate to high sodium consumption. So the focus on the sodium content in processed foods alone may be completely misguided.
8. Summary: How much salt should you eat?
Both published research and anecdotal evidence have shown that the response to salt intake varies from person to person.
You can test your own blood pressure or look for signs of fluid retention (puffiness, tight rings) the day after you've eaten salty foods and compare these results to those following a day of eating less salt. In many cases, fluid retention and elevated blood pressure may be unrelated to sodium intake or only minimally influenced by it.
If you have salt-sensitive hypertension, congestive heart failure, or kidney disease, it may be best to avoid eating a lot of sodium - although the amount that's best for you may require some experimentation, in coordination with your medical provider. Also, keep in mind that eating a high-quality, carb-restricted diet may potentially improve blood pressure, cardiovascular function, and kidney health much more than restricting salt.
However, if you don't have any of these conditions, there isn't any convincing evidence that sodium restriction is beneficial, especially if you follow a low-carb or keto diet. Consuming about 4 to 7 grams of sodium (about 2 to 3 teaspoons of salt) per day is where most of us in the low-carb community will likely feel and perform our best. Occasionally, even more sodium may be needed to replenish increased losses in sweat during hot weather or strenuous physical activity.
And remember, it's always excellent advice to replace highly-processed, low-quality food with minimally-processed, nutritious real food.
