When we refer to “regular table salt,” it is most commonly in the form of sodium chloride, which is also a major constituent of packaged and ultraprocessed foods.
The best approach to finding the “healthiest salt” – which really means the lowest in sodium – is to look for the amount on the label. “Sodium-free” usually indicates less than 5 mg of sodium per serving, and “low-sodium” usually means 140 mg or less per serving. In contrast, regular table salt can contain as much as 560 mg of sodium in one serving.
Other en vogue salts, such as pink Himalayan salt, sea salt, and kosher salt, are high in sodium content – like regular table salt – but because of their larger crystal size, less sodium is delivered per serving.
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Most salt substitutes are reduced in sodium, with the addition of potassium chloride instead.
FDA issues guidance on reducing salt
Currently, the U.S. sodium dietary guidelines for persons older than 14 stipulate 2,300 mg/d, which is equivalent to 1 teaspoon a day. However it is estimated that the average person in the United States consumes more than this – around 3,400 mg of sodium daily.
In October 2021, the U.S. Food and Drug Administration published guidance on voluntary sodium limitations in commercially processed, packaged, and prepared food. The FDA’s short-term approach is to slowly reduce exposure to sodium in processed and restaurant food by 2025, on the basis that people will eventually get used to less salt, as has happened in the United Kingdom and other countries.
Such strategies to reduce salt intake are now being used in national programs in several countries. Many of these successful initiatives include active engagement with the food industry to reduce the amount of sodium added to processed food, as well as public awareness campaigns to alert consumers to the dangers of eating too much salt. This includes increasing potassium in manufactured foods, primarily to target hypertension and heart disease, as described by Clare Farrand, MSc, BSc, and colleagues, in the Journal of Clinical Hypertension. The authors also make several recommendations regarding salt reduction policies:
- Food manufacturers should gradually reduce sodium in food to the lowest possible levels and explore the use of potassium-based sodium replacers to reduce sodium levels even further.
- Governments should continue to monitor sodium and potassium levels in processed foods.
- Further consideration may need to be given to how best to label salt substitutes (namely potassium) in processed foods to ensure that people who may be adversely affected are aware.
- Governments should systematically monitor potassium intake at the population level, including for specific susceptible groups.
- Governments should continue to systematically monitor sodium (salt) intake and iodine intake at the population level to adjust salt iodization over time as necessary, depending on observed salt intake in specific targeted groups, to ensure that they have sufficient but not excessive iodine intakes as salt intakes are reduced.
- Governments should consider opportunities for promoting and subsidizing salt substitutes, particularly in countries where salt added during cooking or at the table is the major source of salt in the diet.
The new FDA document includes 163 subcategories of foods in its voluntary salt reduction strategy.
Salt substitutes, high blood pressure, and mortality
Lowering sodium intake is almost certainly beneficial for persons with high blood pressure. In 2020, a review in Hypertension highlighted the benefit of salt substitutes in reducing hypertension, reporting that they lower systolic blood pressure by 5.58 mm Hg and diastolic blood pressure by 2.88 mm Hg.
And changes to dietary sodium intake can potentially reduce or obviate the need for medications for essential hypertension in some individuals. Although there are only a few studies on this topic, a study by Bruce Neal, MB, ChB, PhD, and colleagues, revealed a reduction in stroke, cardiovascular events, and deaths with the use of potassium-based salt substitutes.
Salt substitutes and sodium and potassium handling in the kidneys
Many studies have shown that potassium-rich salt substitutes are safe in individuals with normal kidney function, but are they safe and beneficial for people with chronic kidney disease (CKD)?
For anyone who is on a renal diet, potassium and sodium intake goals are limited according to their absolute level of kidney function.
There have been case reports of life-threatening blood potassium levels (hyperkalemia) due to potassium-rich salt substitutes in people with CKD, but no larger published studies on this topic can be found.
A diet modeling study by Rebecca Morrison and colleagues evaluated varying degrees of potassium-enriched salt substituted bread products and their impact on dietary intake in persons with CKD. They used dietary data from the National Nutrition and Physical Activity Survey 2011-2012 in Australia for 12,152 participants, 154 of whom had CKD. Replacing the sodium in bread with varying amounts of potassium chloride (20%, 30%, and 40%) would result in one-third of people with CKD exceeding the safe limits for dietary potassium consumption (31.8%, 32.6%, and 33%, respectively), they found.
“Potassium chloride substitution in staple foods such as bread and bread products have serious and potentially fatal consequences for people who need to restrict dietary potassium. Improved food labelling is required for consumers to avoid excessive consumption,” Ms. Morrison and colleagues concluded. They added that more studies are needed to further understand the risks of potassium dietary intake and hyperkalemia in CKD from potassium-based salt substitutes.
The American Heart Association recommends no more than 1,500 mg of sodium intake daily for persons with CKD, diabetes, or high blood pressure; those older than 51; and African American persons of any age.
The recommended daily intake of potassium in persons with CKD can range from 2,000 mg to 4,000 mg, depending on the individual and their degree of CKD. The potassium content in some salt substitutes varies from 440 mg to 2,800 mg per teaspoon.
The best recommendation for individuals with CKD and a goal to reduce their sodium intake is to use herbs and lower-sodium seasonings as a substitute, but these should always be reviewed with their physician and renal nutritionist.
Dr. Brookins is a board-certified nephrologist and internist practicing in Georgia. She is the founder and owner of Remote Renal Care, a telehealth kidney practice. She reported no relevant conflicts of interest.
A version of this article first appeared on Medscape.com.