Large-scale salt substitution holds promise for reducing mortality with no elevated risk of serious harms, especially for older people at increased cardiovascular disease (CVD) risk, a systematic review and meta-analysis by Australian researchers suggested.
The study, published in Annals of Internal Medicine, adds more evidence that broad adoption of potassium-rich salt substitutes for food preparation could have a significant effect on population health.
Although the supporting evidence was of low certainty, the analysis of 16 international randomized controlled trials of various interventions with 35,321 participants found salt substitution to be associated with an absolute reduction of 5 in 1000 in all-cause mortality (confidence interval, –3 to –7) and 3 in 1000 in CVD mortality (CI, –1 to –5).
Led by Hannah Greenwood, BPsychSc, a cardiovascular researcher at the Institute for Evidence-Based Healthcare at Bond University in Gold Coast, Queensland, the investigators also found very low certainty evidence of an absolute reduction of 8 in 1000 in major adverse cardiovascular events (CI, 0 to –15), with a 1 in 1000 decrease in more serious adverse events (CI, 4 to –2) in the same population.
Seven of the 16 studies were conducted in China and Taiwan and seven were conducted in populations of older age (mean age 62 years) and/or at higher cardiovascular risk.
With most of the data deriving from populations of older age at higher-than-average CV risk and/or eating an Asian diet, the findings’ generalizability to populations following a Western diet and/or at average CVD risk is limited, the researchers acknowledged.
“We are less certain about the effects in Western, younger, and healthy population groups,” corresponding author Loai Albarqouni, MD, MSc, PhD, assistant professor at the Institute for Evidence-Based Healthcare, said in an interview. “While we saw small, clinically meaningful reductions in cardiovascular deaths and events, effectiveness should be better established before salt substitutes are recommended more broadly, though they are promising.”
In addition, he said, since the longest follow-up of substitute use was 10 years, “we can’t speak to benefits or harms beyond this time frame.”
Bond University
Dr Loai Albarqouni
Still, recommending salt substitutes may be an effective way for physicians to help patients reduce CVD risk, especially those hesitant to start medication, he said. “But physicians should take into account individual circumstances and other factors like kidney disease before recommending salt substitutes. Other non-drug methods of reducing cardiovascular risk, such as diet or exercise, may also be considered.”
Dr. Albarqouni stressed that sodium intake is not the only driver of CVD and reducing intake is just one piece of the puzzle. He cautioned that substitutes themselves can contain high levels of sodium, “so if people are using them in large volumes, they may still present similar risks to the sodium in regular salt.”
While the substitutes appear safe as evidenced by low incidence of hyperkalemia or renal dysfunction, the evidence is scarce, heterogeneous, and weak, the authors stressed.
“They can pose a health risk among people who have kidney disease, diabetes, and heart failure or who take certain medications, including ACE inhibitors and potassium-sparing diuretics,” said Emma Laing, PhD, RDN, director of dietetics at the University of Georgia in Athens. And while their salty flavor makes these a reasonable alternate to sodium chloride, “the downsides include a higher cost and bitter or metallic taste in high amounts. These salt substitutes tend to be better accepted by patients if they contain less than 30% potassium chloride.”
University of Georgia
Dr. Emma Laing
She noted that flavorful salt-free spices, herbs, lemon and lime juices, and vinegars can be effective in lowering dietary sodium when used in lieu of cooking salt.
In similar findings, a recent Chinese study of elderly normotensive people in residential care facilities observed a decrease in the incidence of hypertension with salt substitution.
Approximately one-third of otherwise health individuals are salt-sensitive, rising to more than 50% those with hypertension, and excessive salt intake is estimated to be responsible for nearly 5 million deaths per year globally.
How much impact could household food preparation with salt substitutes really have in North America where sodium consumption is largely driven by processed and takeout food? “While someone may make the switch to a salt substitute for home cooking, their sodium intake might still be very high if a lot of processed or takeaway foods are eaten,” Dr. Albarqouni said. “To see large population impacts, we will likely need policy and institutional-level change as to how sodium is used in food processing, alongside individuals’ switching from regular salt to salt substitutes.”
In agreement, an accompanying editorial by researchers from the universities of Sydney, New South Wales, and California, San Diego, noted the failure of governments and industry to address the World Health Organization’s call for a 30% reduction in global sodium consumption by 2025. With hypertension a major global health burden, the editorialists, led by J. Jaime Miranda, MD, MSc, PhD, of the Sydney School of Public Health at the University of Sydney, believe salt substitutes could be an accessible path toward that goal for food production companies.
University of Sydney
Dr. J. Jaime Miranda
“Although the benefits of reducing salt intake have been known for decades, little progress has been made in the quest to lower salt intake on the industry and commercial fronts with existing regulatory tools,” they wrote. “Consequently, we must turn our attention to effective evidence-based alternatives, such as the use of potassium-enriched salts.”
Given the high rates of nonadherence to antihypertensive medication, nonpharmacologic measures to improve blood pressure control are required, they added. “Expanding the routine use of potassium-enriched salts across households and the food industry would benefit not only persons with existing hypertension but all members of the household and communities. An entire shift of the population’s blood pressure curve is possible.”
The study authors called for research to determine the cost-effectiveness of salt substitution in older Asian populations and its efficacy in groups at average cardiovascular risk or following a Western diet.
This research was supported by the National Health and Medical Research Council of Australia and an Australian Government Research Training Program Scholarship. Coauthor Dr. Lauren Ball disclosed support from the National Health and Medical Research Council of Australia. Ms. Hannah Greenwood received support from the Australian government and Bond University. Dr. Miranda disclosed numerous consulting, advisory, and research-funding relationships with government, academic, philanthropic, and nonprofit organizations. Editorial commentator Dr. Kathy Trieu reported research support from multiple government and non-profit research-funding organizations. Dr. Cheryl Anderson disclosed ties to Weight Watchers and the McCormick Science Institute, as well support from numerous government, academic, and nonprofit research-funding agencies.