Lower-sodium, potassium-enriched salt substitution: An opportunity for improving blood pressure in Jamaica?

1. Background

High systolic blood pressure (≥115 mmHg) is the leading modifiable risk factor for cardiovascular disease and the Caribbean has the highest prevalence of hypertension in the Americas [1]. The Pan American Health Organization (PAHO) reports that 35 % of adults in Latin American and the Caribbean (LAC) have hypertension and, of those on treatment, about one-third are controlled. [2]. The World Health Organisation (WHO) estimates that Jamaica's age-standardized hypertension prevalence for adults 30–79 years was 46 % in 2019 with only 19 % of hypertensive patients at blood pressure target of <140/90 mmHg [3]. It is estimated that Jamaican $1.4 billion dollars was spent in subsidy for hypertension medications in 2020 [4]. Population-based strategies are needed to reduce the burden and cost of hypertension.

Salt substitution as a population intervention.

Facilitators

• •Strong evidence of effectiveness
• •Increasing market share for other salts (e.g. sea salt)
• •Similar taste to regular salt when used in food preparation
• •Previous private sector partnership to implement fluoridated salt as a public health strategy
• •Sole salt manufacturer >40 years in Jamaica
• •Social marketing and mass media

Barriers

• •Higher price compared to regular salts
• •Possibility of public resistance to use of salt substitute
• •Lack of awareness about potassium enriched salt
• •Limited data on salt substitution use in persons with chronic kidney disease
• •Limited availability

2. Sodium and potassium consumption

Excessive sodium and insufficient potassium consumption are principal causes of high blood pressure. Worldwide 1.65 million deaths annually are attributed to high blood pressure caused by excess sodium consumption, including 15.6 deaths per 100,000 people in Jamaica [5]. Sodium reduction can lower blood pressure, prevent hypertension and reduce the number of anti-hypertensive medications required for blood pressure control. It is also associated with lower risks of cardiovascular disease and all-cause mortality [6]. Each 1.0 g/day lower level of sodium intake results in one-fifth reduction in cardiovascular disease risk (RR 0.80, 95 % CI 0.66–0.97) [6] with greater impact for older persons, nonwhite populations and persons with hypertension [7]. The WHO recommends sodium consumption of ≤ 2g/day but the 2023 Jamaica Salt Consumption Study reported mean intake of 3.6 g/day, with two-thirds of Jamaicans consuming more sodium than recommended [8]. Meanwhile mean potassium consumption (2.1 g/day) was below the WHO recommended minimum (3.5g/day) and almost 90 % of Jamaicans consumed inadequate potassium [8]. The survey found that dietary sodium mostly comes from discretionary salt, that is, salt added when cooking at home.

3. Blood pressure control and sodium reduction initiatives

The Caribbean has several policy initiatives to address hypertension and cardiovascular diseases [[9], [10], [11]]. The 2007 Port of Spain Declaration was the first Summit of Heads of Government to focus on non-communicable diseases (NCDs) [9]. This was followed by international commitments including the United Nations High Level Meetings on NCDs (2011, 2013, 2014 and 2018), the WHO Global Action Plan for Prevention and Control of NCDs (2013–2020) and locally, the PAHO Regional Plan of Action for the Prevention and Control of NCDs in the Americas (2013–2019) [10,11].

These initiatives identified the need for better ways to treat and prevent hypertension but policy implementation has been sub-optimal. A PAHO evaluation of the Port of Spain Declaration showed that none of the signatory countries had fully implemented all 15 mandates [9]. Subsequently, PAHO identified that the least progress was made in addressing unhealthy diets [12]. Only 5 countries, excluding Jamaica, had a policy on sodium reduction and implementation was limited in all [12].

4. Progress with cutting sodium intake and the potential for switching to salt substitute

Jamaica is not alone in failing to progress with sodium reduction strategies based on cutting salt intake. The key challenges for initiatives to cut salt are twofold. Firstly, removing salt from food may make it less palatable to consumers; secondly, it changes food preparation and preservation behaviors that neither individuals nor corporations have been able to achieve.

Salt substitutes, also called low-sodium salts or potassium-enriched salts, are alternatives to regular salt with some of the sodium chloride replaced with potassium chloride. Salt substitutes produce the same salty taste as regular salt, and they can be used as a direct one-to-one switch when seasoning food. They lower blood pressure by reducing dietary sodium and increasing dietary potassium. These effects are additive, and may be synergistic with larger blood pressure lowering achieved with potassium supplementation when dietary sodium is high [7,13]. Large clinical trials show that salt substitutes provide benefits for normotensive and hypertensive persons [14,15] with protection against stroke, major cardiovascular events and premature death [16,17]. The high acceptability of salt substitute was highlighted by the largest trial to date, with 92 % of participants assigned to the salt substitute group using it after 5 years. In addition, salt substitutes do not significantly alter the flavor of food compared to regular salt when used in food preparation [18].

For Jamaica, it is estimated that switching salt supply from regular salt (100 % sodium chloride) to salt substitute comprised of 25 % potassium chloride and 75 % sodium chloride can avert about 12 % (760/6211) of cardiovascular deaths annually. In addition, switching would prevent a further 10 % (2018/20,133) of non-fatal cardiovascular events annually [19]. While available evidence is largely for discretionary salt, the greatest benefits are expected from addressing discretionary and non-discretionary sources of salt simultaneously.

5. Public health success in Jamaica from a salt intervention

One of Jamaica's public health successes is the introduction of fluoridated salt to address dental caries. In the 1980s fewer than 3 in every 100 children were free of caries and about 6.7 % had decayed, missing or filled teeth [20]. Fluoridated water was the standard approach in other countries, but salt was the best medium for Jamaica since water distribution services were then limited to urban areas. Rainwater or other sources which were low in fluoride were used for drinking water. Prior evidence on salt fluoridation in Colombia showed similar reductions in dental caries from the use of fluoridated salt (50 % compared to control community) and fluoridated water (60 %) [20].

In 1987, a dentist worked with the Ministry of Health to partner with Jamaica's only salt producer to sell fluoridated salt [21]. The Ministry of Health led Parliament in establishing the regulatory framework. Engineers from the salt factory fluoridated salt by adding 250 mg of potassium fluoride per kilogram of salt and purchased necessary equipment (US $3000). This cost was recovered by a slight increase in product cost. The Ministry of Health provided biological and chemical monitoring of the salt while the company performed quality control and the Jamaica Bureau of Standards monitored fluoride concentration. By 1995 the index of dental caries severity in 6- and 12- year old children fell by over 80 % [21]. This cost-effective intervention has a lasting impact on children's wellbeing, particularly those from vulnerable households.

Salt substitution is another example of creative problem-solving that can be implemented with large scale impact in Jamaica. The Industrial Chemical Company being the sole salt manufacturer in Jamaica for more than 40 years plus the history of government collaboration to address dental caries is an opportunity for a population-wide intervention. Other salt formulations were successfully launched after fluoridated salt including sea salt which is marketed as a natural option. Its success may be an indication of the population's interest in “healthy” options. This is consistent with a recent needs assessment for the CATCH study (Caribbean and South America Team-based Strategy to Control Hypertension) which showed that hypertensive patients in Jamaica were receptive to lifestyle interventions including dietary recommendations to improve hypertension control. Political will is also high as the Jamaican Government has allocated significant financial resources to address NCDs. The Ministry of Health and Wellness has recently promulgated a National Strategic and Action Plan for the Prevention and Control of NCDs as well as national guidelines for hypertension management. Various campaigns are being implemented to increase physical activity (“Jamaica Moves” campaign) and to increase awareness and self-management of NCDs (“Know your Numbers” campaign).

6. Considerations for use of salt substitutes in Jamaica

Recognizing the potential of salt substitute, in January 2025 the WHO guideline highlights switching discretionary salt to salt substitute as a novel strategy to address challenges presented by traditional approaches to cutting discretionary salt intake. Important considerations for Jamaica in this regard include:

Improving the policy environment for implementation and scale-up of salt substitutes: Despite the strong evidence base and WHO’s recommendation for use of salt substitutes, Jamaica’s recent National Strategic and Action Plan for NCDs does not include salt substitutes as a strategy and emphasis is placed on cutting salt intake. Potassium-enriched salt is not manufactured locally. Therefore engagement of the Government and local salt manufacturer will be an important first step to recognize salt substitute as a national strategy to reduce the burden of hypertension. This will also provide opportunities to strengthen the policy and regulatory environment around salt manufacturing and use in different settings. Engagement of multilateral organizations such as WHO/PAHO, and UNICEF will be important for advocacy, technical support and resource allocation.

Risk of high blood potassium levels (hyperkalaemia) in patients with kidney disease: No trial to date has shown increased risk of adverse clinical outcomes from hyperkalaemia though most studies exclude people with serious kidney disease [16,17]. In one trial done in elderly care homes that included people irrespective of kidney function [17], there was increased risk of hyperkalemia, though no associated adverse clinical outcomes were recorded, and there was protection against cardiovascular events. Potassium-enriched salts are recommended in clinical guidelines for persons with hypertension and normal kidney function [22]. However, the National Institute for Health and Care Excellence (United Kingdom) cautions against their use in older adults, pregnant women as well as in persons with diabetes, and conditions or medications that interfere with potassium homeostasis (e.g. ACE inhibitors or angiotensin II receptor blockers). A pilot study in Jamaica will provide insight into the risk of hyperkalemia in our population and identify persons at-risk. We anticipate a good safety profile since the prevalence of CKD in Jamaica (15 %) is lower than that recorded in rural China (29 %) where community-based trials of salt substitutes did not show significant risk of hyperkalemia [23,24]. Further studies are needed in patients with impaired kidney function because of the theoretical risk of hyperkalaemia. Finding the right balance between managing risk in kidney disease and accruing population benefit is vital because large net health gains are anticipated with switching to salt substitute, even amongst patients with kidney disease [25].

Cost: Salt substitute products are on average 1.7 times more expensive than regular salt but prevention of major cardiovascular events, particularly in the lowest income groups, leads to substantial cost savings in the long-term [26,27]. While still a low-cost commodity, the higher price of salt substitute may deter use in Jamaica and could worsen health inequities. Local production and policies including government subsidies may provide affordable salt substitutes and ensure widespread adoption, scalability and reduced health disparities.

Awareness and availability: While salt substitutes were available in about 50 countries worldwide (including Jamaica), in no country did salt substitute constitute a significant proportion of total salt sales. Social marketing and mass media campaigns will be integral for increasing awareness about the health benefits of salt substitutes and avoiding use if kidney disease is present while preserving the taste of traditional foods. Such campaigns have been used successfully in other public health programmes including Jamaica's HIV response.

Impact on dietary iodine and Fluoride: Because salt substitutes can be iodized there is no requirement for changes to strategies for prevention of iodine deficiency. However the feasibility of joint iodization, fluoridation and potassium-enrichment needs to be confirmed because salt is the vehicle for delivering fluoride for prevention of dental caries in Jamaica [28].

Integration with other Public Health Initiatives: Exploring the potential for integration of salt substitute with HEARTS [29] and local initiatives to improve blood pressure care could provide a rapid way of identifying opportunities and challenges specific to introducing salt substitute in Jamaica and assessing safety concerns. Additionally it would also allow for evaluation of safety concerns around precipitating hyperkalemia in these patients, particularly those with chronic kidney disease. It will be important to engage organisations spanning government, health bodies, the salt industry and consumer organisations.

7. Conclusion

Hypertension is a formidable threat to Jamaica's health and development. Salt substitute is a novel, low-cost, non-pharmacological approach to this public health problem. Many actions will be required prior to salt substitute use in Jamaica but the history of nationwide iodization and fluoridation of Jamaica's salt supply and the strong political will to address NCDs suggest that potassium addition should be a highly tractable proposition.

Ethical statement

This commentary did not involve human subjects or animals in its research. Neither ethical approval nor individual consent was applicable.

Contributor statements

MKTR, TSF and BN are responsible for conceptualization, MKTR and JPD produced the first draft and integrated comments from all authors into the final version for submission. All authors reviewed, edited and finalised the manuscript. All authors have seen and approved the final manuscript.

Funding

None.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Past and planned trials led by Bruce Neal have been provided with potassium-enriched salt by Klinge Chemicals. The other authors have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.