Does restricting sodium intake cause more problems than it solves?
The story of salt — as a favorite food flavoring and, at the same time, public-health enemy — continues to unfold.
Following a plot line familiar in the realm of nutrition, the salt saga pits two well-intentioned and strongly held perspectives against each other. On one side, public-health experts have warned of salt’s dangers for nearly 50 years, stressing its association with high blood pressure and heart disease. They insist we’d all be better off if we ate less of it. A lot less.
On the other side, a growing number of researchers and clinicians call for a more nuanced assessment. They argue that salt (a mineral known chemically as sodium chloride) is a biological -necessity and not inherently problematic — at least not for everyone.
They point to inconsistent findings in the literature regarding sodium’s role in raising blood pressure, and they caution against unintended consequences when we don’t get enough sodium.
Creating more confusion, the terms “salt” and “sodium” are often used interchangeably in health warnings. We eat salt — which typically contains 40 percent sodium and 60 percent chloride — but it’s the sodium that concerns health experts.
Americans consume an average of 3,400 mg of sodium per day, the amount in about 1½ teaspoons of salt. Nearly 70 percent of this comes from industrially processed foods — fare that is not only excessively high in sodium, but also sugar, refined grains, and other ingredients that research has shown to cause elevated blood pressure and other metabolic conditions that can lead to heart disease.
Many experts argue that the salt on our tables is not as much of a problem as the processed-food context in which we most often consume it (the quality of table salt does matter — more on that later). The solution, they say, is less about managing how much salt we’re getting and more about improving our overall diet.
“If you eat a healthy and varied diet, you probably do not have to worry about your sodium intake,” explains prominent sodium researcher Niels Graudal, MD.
Your Body and Salt
Salt plays a vital and beneficial role in human health. The sodium chloride molecule is a key factor in dozens of biological processes, including muscle contraction (think pumping heart), nerve-impulse function (think firing brain neurons), and blood-pressure and blood-volume regulation.
“Sodium also helps the body absorb vitamin C, and drive vitamin C into the brain and into the bone,” explains cardiovascular research scientist James DiNicolantonio, PharmD, author of The Salt Fix. “The other half of salt — chloride — makes up hydrochloric acid and helps with the digestion of food and nutrient absorption. It also helps to reduce bacterial overgrowth.”
The 2015–2020 U.S. Departments of Agriculture and Health & Human Services Dietary Guidelines recommend limiting daily sodium intake to 2,300 mg, roughly equivalent to 1 teaspoon of salt. Other public-health organizations, including the American Heart Association and the Academy of Nutrition and Dietetics, set daily sodium targets as low as 1,500 mg — the amount in less than ¾ teaspoon of salt.
Some health experts find these recommendations overly aggressive. They point to similar high-profile crusades against saturated fat and cholesterol that were later shown to be based on faulty scientific hypotheses.
Indeed, studies show that too little sodium can lead to increased cholesterol and triglycerides in the bloodstream, says Graudal. It also disrupts hormonal balance: The endocrine function that conserves salt in the body (known as the renin-angiotensin-aldosterone system) is activated when you’re low on sodium, he explains. “And increased renin is a prognostic marker for increased mortality.”
Lower sodium intake has also been associated with greater insulin resistance, notes Hillel Cohen, DrPH, MPH, an epidemiologist at Albert Einstein College of Medicine in New York City — though he cautions that there is likely significant variation from person to person.
Individual sodium needs can differ dramatically as well, says Cohen, and are affected by activity level, water intake, genetic predispositions, and other factors.
Further, many common health conditions increase our salt requirements, explains DiNicolantonio. Inflammatory bowel disease, celiac disease, and gluten intolerance, for example, inhibit salt absorption; other conditions, such as sleep apnea, hypothyroidism, and kidney disease, cause salt loss. Dietary factors also play a role in individual salt requirements, including caffeine consumption, which exacerbates salt loss from sweat and urine.
In other words, each of us would be wise to take broad public-health messages about sodium with a grain of salt.
“It took more than 30 years to turn around the low-fat, high-carbohydrate recommendations that had been mistakenly made, albeit with good intentions,” says Cohen. “So, it’s not surprising that an extreme low-salt position still lingers, despite growing evidence to the contrary.”
“Guidelines that affect millions of people should be made on the basis of unambiguous scientific evidence,” Graudal notes. “I think the current sodium-reduction guidelines could wind up inadvertently killing more people than they save.”
Good Salt, Bad Salt
Food manufacturers use sodium as a preservative, texturizer, and chemical catalyst — and as a seasoning that contributes to the amped-up flavor that makes many of these foods so hard to resist.
Sodium is found in surprising places: Much of the raw chicken sold in supermarkets, for instance, is injected with salt water, giving a 4-ounce serving up to 400 mg of sodium, more than five times that found in a same-size serving of unadulterated chicken. (For more on how processed foods hijack your taste buds, see “Take Back Your Tastebuds.”)
And the sodium value listed on the nutrition label of packaged, jarred, or canned food represents not only sodium chloride but also any added sodium bicarbonate (baking soda); monosodium glutamate (MSG); sodium benzoate (a preservative considered a potential trigger for kids with attention deficit hyperactivity disorder, or ADHD); sodium saccharin (the sweetener also known simply as saccharin); and sodium nitrate and nitrite (preservatives associated with increased cancer risk).
“Our bodies are not designed to handle the tsunami of sodium delivered day in and day out by processed foods,” says integrative nutritionist Kathie Madonna Swift, MS, RDN, LDN, cofounder of the Integrative and Functional Nutrition Academy.
Not only are sodium levels in processed foods higher (and of a different nature) than they would be if we salted to taste, but they’re also missing potassium and other synergistic minerals that have a protective effect on cardiovascular health. In addition, they crowd out whole foods that deliver nutrients in the proportions our bodies are designed to utilize.
“Because we don’t eat enough high-potassium vegetables and fruits to balance it out, our sodium-to-potassium ratio is totally lopsided,” says Swift. This is why reduced-sodium foods are not the best answer, even for those who do need to lower their sodium intake.
“It’s all about electrolyte balance,” says functional-medicine nutritionist Julie Starkel, MS, MBA, RD. “I always talk to my clients about ways to get more minerals.”
Starkel recommends limiting processed foods and enjoying whole foods, such as grassfed meat, vegetables, and unrefined grains, seasoned to taste with sea salt. “Sea salts contain more than 15 percent trace minerals and have been proven to raise trace-mineral levels in the body,” she says. (See “Make a Salt Swap,” page 39, for more on choosing natural salts.)
So instead of obsessing about salt, ditch the sugar, low-quality processed fats, and refined flours — all of which will likely do more harm to your health. Let high-quality salts enhance your enjoyment of the whole foods your body needs, such as bitter greens, which are high in potassium, magnesium, and other minerals.
“Salt can be a gateway to healthier eating,” says DiNicolantonio.
What About Salt’s Role in Blood Pressure and Heart Disease?
More than 360,000 Americans die due to complications from high blood pressure each year. But the case for the public-health initiative to restrict sodium in an effort to reduce blood pressure, and by extension cardiovascular disease, is not ironclad.
First, not everyone is sensitive to salt. “The data is fairly consistent that about 80 percent of people with normal blood pressure are not salt sensitive,” explains cardiovascular research scientist James DiNicolantonio, PharmD. He cites research indicating that 75 percent of people with prehypertension, and 55 percent with hypertension, are also not salt sensitive.
Plus, efforts to reduce sodium intake are not widely associated with low blood pressure and reduced risk for cardiovascular disease. A recent Cochrane Review meta-analysis found that salt-reduction initiatives resulted in only slightly reduced blood pressure among people without high blood pressure. Among study subjects who were hypertensive, there was only “weak evidence of benefit.”
And, while there is no simple way to test your body’s sensitivity to salt, experts say that even if you have high blood pressure, salt may not be the culprit.
“Hypertension, like fever, is not a diagnosis but rather a description,” explains Paul Rosch, MD, FACP, chairman of the board of directors at the American Institute of Stress. “The vast number of people you see with hypertension have no specific, obvious cause for it.”
So, when it comes to managing cardiovascular risk, how much sodium is too much — and how much is too little? Here’s what some of the latest research says.
- Study participants whose daily sodium consumption fell between 4,000 and 6,000 mg suffered fewer heart attacks and strokes than those whose intake fell on either side of that range, according to a 2014 report published in the New England Journal of Medicine. The review, which looked at 100,000 people in 17 countries over an average of nearly four years, also found that higher potassium intake was associated with lower risk of both major cardiovascular events and death.
- High sodium intake, when compared with moderate consumption, was associated with an increased risk of cardiovascular events and death in hypertensive populations. Yet researchers found no link among people without high blood pressure, according to a 2016 study published in The Lancet. The study also showed a connection between low sodium intake and increased risk of cardiovascular events and death in those with or without hypertension.
- People who consumed less than 2,500 mg of sodium per day had higher blood pressure than those who consumed higher amounts — and those who consumed higher combined intakes of sodium (3,717 mg daily on average) and potassium (3,211 mg daily on average) had the lowest blood pressure, according to a study presented by Lynn L. Moore of Boston University School of Medicine at the 2017 American Society for Nutrition Scientific Sessions and Annual Meeting.
These studies and others suggest a J-shaped relationship between sodium and cardiovascular risk: People whose intake falls above or below a certain level tend to experience increased health risks. The studies also highlight the potential protective effect of the electrolyte potassium on cardiovascular health.
“As with any thresholds, the thresholds that have been identified for the J are not exact,” notes epidemiologist Hillel Cohen, DrPH, MPH. “They are rough estimates and will vary from study to study.”
Research has shown that salt sensitivity, independent of blood pressure, is a risk factor for cardiovascular morbidity and mortality. But risk also represents an interplay of genes and environment, including diet and lifestyle. Cohen recommends that those in at-risk categories consult with clinicians to discuss nonpharmacological methods of reducing blood pressure.
“No matter what group you are in, what’s true for the average is not necessarily true for the individual,” he says. “Broad assumptions about categories of people may not apply.”
This originally appeared as “The Great Salt Debate” in the March 2018 print issue of Experience Life, and is an updated version of “Shaking Out the Truth About Salt.”