Sodium reduction
salt intake and initiate programmes to reduce it. WHO Member States, for example, have agreed to reduce the global population’s salt intake by 30% by 2025. China’s central government is aiming for a 20% reduction by 2030 as a key component in its ‘Healthy China 2030’ initiative.
In the UK, work on salt reduction began back in 2004 when the Scientific Advisory Committee on Nutrition recommended average salt intake should be reduced to 6g per day to reduce the risk of high blood pressure and cardiovascular disease (CVD). CVD causes around one quarter of all deaths in the UK and is the largest cause of premature mortality in deprived areas. In China, where salt intake is among the highest in the world at around 11g per day, CVD accounts for 40% of all deaths.
Time for change
Although the link between sodium and blood pressure has been investigated before, research has not affected wholesale change in global salt consumption. Indeed, a vocal minority has always decried the link between salt and CVD, though it is hoped the latest research will quieten those voices. “It has been a confusing space. There are two main types of study that can be done to investigate the link between sodium intake, blood pressure and CVD,” says Dr Bruce Neal, executive director at The George Institute for Global Health Australia and professor of medicine at the University of New South Wales Sydney. “You can do an observational study, where you ask people how much salt they eat and track them over time to see their health outcomes. The results from these studies can be confounded by other factors and give misleading results. “For example, if you have had a prior heart attack or stroke you may well have reduced the amount of salt you eat,” he adds. “In an observational study, these people are counted as low salt consumers, despite years of eating high salt before their heart attack. And because they have now already had one heart attack this means they are at very high risk of having another one. This sort of problem can skew the results because it makes it look like people who eat less salt have higher, not lower, risks.” A physician by training, Neal has been a researcher for 20 years. His long-standing interest has been in blood pressure and how excess sodium consumption affects it, and he has been eager to replicate the process of drug therapy trials in the food and nutrition space. Consequently, he was involved in China’s recent Salt Substitute and Stroke Study (SSaSS), which sought to emulate the kind of randomised trials that pharmaceutical companies perform when seeking regulatory approval for a new drug treatment.
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www.ingredients-insight.com
“The second stronger type of study is a randomised trial,” he remarks. “By randomly assigning people to either salt or a salt substitute you know that everything was equal between the two groups when you started. And that means you can infer whatever results you see at the end to be the effect of the salt substitute. In addition, we wanted to study effects on stroke and heart attacks, not just blood pressure. This meant we had to go big because even in high-risk people these sorts of outcomes are fortunately fairly infrequent. No one had done a large enough study to define effects on stroke and heart attack before.”
The global supply chain was already switched to iodised salt 50 years ago.
“If you have had a prior heart attack or stroke you may well have reduced the amount of salt you ear. In an observational study, these people are controlled as low salt consumers, despite years of eating high salt before.”
Dr Bruce Neal
Spanning five years, SSaSS is one of the largest dietary interventions ever conducted. It enrolled more than 20,000 participants from 600 rural villages in China. All of the participants had a history of stroke or were aged over 60 with high blood pressure. “We did the study in rural China because they eat a lot of salt there, and the salt is largely added when preparing food in the home,” says Neal. “This means you can change the type of salt people eat quite easily. In the UK, 80–90% of salt comes in processed and packaged food, so it is hard to change to a salt substitute.”
“Also, China has a rural health insurance scheme in which everyone in the study was enrolled, so we could search hospital records every six months for stroke, heart attack and death,” he adds.
30% WHO 81
WHO Member States have agreed to reduce the global population’s salt intake by 2025.
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