CO-AUTHORED BY: James J. DiNicolantonio, PharmD
BRIEF BIO: Dr. DiNicolantonio is a research scientist at Saint Luke's Mid America Heart Institute in Kansas City, Missouri
LONGER BIO AND PHOTO: http://www.saintlukeshealthsystem.org/dinicolantonio
New York City is set to become the first city in the United States to require sodium warnings on menus. The city’s Board of Health voted unanimously to require large chain restaurants, theaters, and ballparks to post warnings (a salt-shaker symbol in ominous black triangle) for any item containing more than 2,300mg of sodium.
2,300 mg of sodium is the upper level of intake recommended by existing Dietary Guidelines for Americans and by the 2015 Dietary Guidelines Advisory Committee. But are these recommendations actually justified? And will labeling appropriately focus consumer attention and improve public health?
Problematic Guidance on Dietary Sodium
Unfortunately, a growing body of evidence suggests that current guidance on dietary sodium may actually be misdirected. Moreover, the effect of sodium labeling could be to direct attention away from bigger problems with nutrition and make consumers decidedly less healthy.
Just as background, the rationale for calling attention to sodium at all relates to blood pressure, the leading risk factor for the #1 cause of death in the US and NYC: heart disease. But the link between sodium and blood pressure is actually more-inconsistent, less-pronounced, and more-nuanced than most people realize, and the link between sodium and heart disease represents a leap in logic.
In biology, just because A (sodium) leads to B (blood pressure) and B (blood pressure) leads to C (heart disease) does not mean A (sodium) necessarily leads to C (heart disease). In other words, even though higher sodium intake might in some instances raise blood pressure, it might not lead to heart issues, and lower sodium intake might not protect hearts or health.
The Importance of Sodium in the Diet
It is worth noting that sodium is an essential nutrient. Although most people have been conditioned to believe that the less sodium they consume the better, evidence suggests that somewhere between 3 to 6 grams of dietary sodium per day may not only be safe, but optimal for hearts and health.
Across diverse populations, eating habits, and time, sodium intake is remarkably stable. Average intake in Western populations consistently falls between about 3 to 5 grams daily, regardless of specific food offerings or public-health interventions. Our bodies recognize the need to maintain sufficient levels of sodium, and sodium intake is in large part regulated through unconscious internal controls.
The Problem of Low Sodium Intake
When people consume relatively lower amounts of sodium, blood pressure may fall to a small degree, although in some people reducing sodium intake can actually increase blood pressure. In those seeing their blood pressure lowered with reduced sodium consumption, decreases might be only as much as 1-4 mmHg on average (on a scale where up to 120 mmHg is considered normal).
Regardless of possible effects on blood pressure though, individuals consuming less sodium than around 3 grams per day actually experience greater risk of heart attacks, stroke, and early death. Conversely, individual consuming greater than about 5 grams of sodium daily do not seem to have greater risk for heart attacks, stroke, or early death (specifically in population-representative samples adjusted for appropriate confounders).
The detrimental, sometimes deadly, effect of low sodium intake may be due sodium’s other effects on the heart and blood vessels. For instance, reducing sodium intake may stimulate hormones that increase heart rate, cardiac workload, and cardiac stress, and lead to unhealthy levels of blood cholesterol. People with even low-normal sodium levels in their blood are at greater risk of death from heart attacks and stoke.
Health Consequences for Vulnerable Groups
Initiatives aimed at lowering sodium consumption could be a decidedly bad thing for public health. Harmful effects may be particular problems for society’s vulnerable groups.
NYC Health Commissioner, Dr. Mary Basset, rightfully worries about premature mortality rates among black and Latino New Yorkers. But it is precisely these New Yorkers who may be harmed most by initiatives aimed at dietary sodium restriction. Diabetes, kidney disease, and heart disease are all more prevalent among minority groups, and the respected Institute of Medicine (now the National Academy of Medicine) has determined that sodium intake as low as recommended for people having these medical conditions may cause harm.
Broader Dietary Considerations
Importantly, net effects on health from dietary intake relate not just to the amount of sodium in any given menu item but to that menu item’s other constituents and to all other food items in the diet. After all, people eat foods, not isolated food components like sodium.
Other components of food may mitigate unhealthy effects of unusually high-sodium intake. Potassium, for example, is associated with lower risk of heart attack, stroke, and dying early. Eating vegetables (good sources of potassium among other healthy components) that are generously seasoned with a saltshaker is not likely to undo the benefits those vegetables provide.
However, the predominant source of sodium in the diet is not salt added to whole foods by the saltshaker. It is salt incorporated into processed items in industrial plants and prep kitchens.
Admittedly, there are many items on NYC menus containing incredible amounts of sodium. But it is not the sodium in these items that is the problem, per se. The problem is the items themselves.
The items that NYC’s new sodium initiative will highlight will generally be industrial formulations of ultra-processed ingredients. In particular, items will be full of refined starches and added sugars, which themselves may constitute greater risk for hypertension and heart disease than sodium.
Unintended Effects on Foods and Diets
When NYC’s saltshaker labeling takes effect, food companies will be incentivized to reduce sodium in their high-sodium items. The companies will inevitably need to replace the salt with something else to achieve palatable products. Often, what will replace the salt is sugar.
Sugar may increase blood pressure through a variety of mechanisms. A diet high in added sugars has been found to increase blood pressure and cause a 3-fold increased risk of death due to cardiovascular disease. Will incentivizing industry to provide, and customers to consume, products higher in sugar be good for public health?
Even if food companies did not modify their high-sodium products at all except for subtracting out the sodium (a feat which would be impossible in actuality due to palatability constraints), consumers might still wind up taking in more sugar (as well as more unhealthy fats and various other ultra-processed artificial ingredients: e.g., colors, flavors, fillers, stabilizers, emulsifiers, etc.). Recall that sodium intake is highly stable across populations and unconsciously regulated. If sodium content of food items goes down, consumers will need to consume a greater quantity of items or a greater number of items to get the sodium their bodies demand (and they will get bigger doses of all the other unhealthy constituents in those items as a consequence).
Would individuals possibly ordering and eating more “now lower in sodium” nachos, processed meats, and saucy noodle and rice dishes be a good thing? Certainly for businesses it would, which is why some companies may embrace NYC’s sodium-labeling initiative or protest only half-heartedly against it. But for consumers, it may mean eating more in general and more unhealthy stuff specifically.
A Path Forward for Public Health
Sodium labeling is emblematic of other misdirected public health initiatives focused on single food components. Years ago, when campaigns focused on dietary fat, the food industry substituted starches and sugars and the result was greater obesity and higher rates of chronic diseases. Today, with initiatives like those focused on sodium, the result is likely to be the same: food companies will engineer substitutions that make unhealthy products perhaps just as unhealthy—or even more so.
The time has come to stop focusing on food components and start focusing on whole foods and whole diets. If the NYC health department wants a symbol to accompany menu items at various city eateries, then an indicator of overall nutritional quality would be far superior. Scoring systems already exist that might be applied. In the interim, continued focus on isolated menu constituents, particularly sodium, is likely to produce the exact opposite effects of those intended. What we need is initiatives that are worth their salt.