Dr Catherine Conlon: Should we introduce mandatory limits on salt in our food? 

Hypertension Awareness Month in May aimed to increase global awareness about high blood pressure (BP) as the leading preventable cause of premature death worldwide.

Unfortunately, Ireland has one of the highest rates of high BP in the world, as well as ranking among the lowest in terms of diagnosis, treatment, and control of the condition.

This matters: high blood pressure, the ‘silent killer’, significantly increases the risk of heart attack, stroke, kidney disease and premature death. Yet, early detection, regular monitoring and sustained treatment can prevent most conditions caused by sustained high BP.

Just over half (55%) of ischaemic heart disease, half (50%) of ischaemic stroke, and more than half (58%) of other cardiovascular conditions have been attributed to high BP. It is the single biggest risk factor globally for ‘all cause mortality’, leading to just under 10 million deaths a year with 1.4 billion people affected.

A study in The Lancet (2021) of people from 12 high-income countries, found that Irish men and women were least likely to have been diagnosed with high blood pressure, given medication to treat it, or to have it controlled.

Treatment is a combination of medication and lifestyle factors; including weight management, physical activity, salt restriction, alcohol reduction and stopping smoking.

However, one country has shown astounding success in the management of hypertension, demonstrating just what can be achieved with sustained political will. 

Over three decades, Korea has managed to cut stroke deaths by a remarkable 80%. How did they do it?

Former director of the Centres for Disease Control and Prevention and NYC Health Commissioner, Dr Tom Frieden described, in his recent newsletter, the policy changes that led to this achievement.

In 1990, stroke killed South Koreans at a rate of 248 per 10,000. By 2023, that had dropped like a stone to 32 – a fall of 87%.

This was achieved by a series of deliberate choices, sustained across successive governments, leading to plummeting hospitalisations, disability, strokes and heart attacks.

“The story deserves to be much better known,” said Dr Frieden, “because Korea has earned the credit and because every country in the world can make progress at least this fast.”

'Ingredients for success'

Rather than investing in awareness campaigns, the first step was to ensure every adult had a regular medical provider whose job was to keep blood pressure in check, and their performance was measured on how well they achieved it. Health professionals were required to identify those at risk, follow them up and record their successes.

It used standard medications – just one or two anti-hypertensive medications - to simplify treatment. Medications were free for low-income patients and heavily subsidised for older adults.

Secondly, in 2012, the government implemented a National Plan to Reduce Sodium Intake – working with manufacturers, schools, restaurants, and households to cut salt out of the national diet. The government funded research to help companies reformulate their products.

Within a few years, Koreans had reduced their sodium intake by almost a quarter, with plummeting rates of stroke and heart disease.

“None of this required exceptional technology, wealth, or anything specific to Korean culture,” Dr Frieden concluded. “A group of dedicated advocates pushed for it and never gave up. The ingredients for success – a regular provider, consistent treatment, free medicines, and smart food policy – are possible in most countries.”

Do we need changes at population level?

In Ireland, a quarter of deaths are due to cerebrovascular disease, and it is estimated that an incredible 80% of premature heart disease and stroke is preventable.

In late 2023, the Irish Heart Foundation launched a paper, Primary Prevention of Cardiovascular Disease: Best Practice and Lessons for Ireland, compiled by Prof Ivan Perry of the School of Public Health, UCC, recommending radical action – similar to Ireland’s 2004 ban on smoking in the workplace – to deal with cardiovascular disease and other diseases.

Key recommendations include a complete ban on the marketing of food and drinks high in fat, sugar and salt, and an increase in the legal age of tobacco from 18 to 21 - now due to be implemented in 2028. But the evidence shows that a mandatory limit on salt in the manufacture of bread and other processed foods leads the way as the cheapest strategy to reduce cardiovascular disease.

Cardiovascular disease accounts for almost 10,000 deaths in Ireland every year, 30% of all deaths. Diet is a key risk factor – via indirect effects on risk factors such as body weight, diabetes and blood pressure.

Another critical risk factor is salt. As BP rises, so does the risk of heart disease and stroke. But contrary to what you might expect, most heart and stroke events happen at the lower end of the BP scale of about 130mmg Hg/ 80mm Hg because of the large numbers of the population with BP at this level.

Given that clinical guidance does not recommend treatment at the lower end of the BP scale with medication, population wide interventions that focus on the underlying causes of BP – including suboptimal diet, physical inactivity, and alcohol intake in the whole population - are critical. 

The Korean success story is a case in point of just how impactful these nationwide interventions can be to cause heart disease and stroke to rapidly plummet.

Mounting evidence shows clearly that high levels of salt in the diet is the major cause of raised BP and a reduction in intake lowers BP and cardiovascular risk. The impact would be greatly advanced if it formed part of a suite of measures that included food labelling (front of pack), public sector procurement, and mass media campaigns, similar to approaches used in Finland and Japan.

A comprehensive, evidence-based report has spelt out the benefits of mandatory limits on the salt content of bread and processed meat to significantly reduce deaths and illness from heart disease and stroke in an ageing population. How long before Minister for Health, Jennifer Carroll McNeill and the Department of Health see it that way?