March 11-17 is World Salt Awareness Week | After a century of study experts agree that there is direct link between high levels of sodium and high blood pressure By Dr. Anuji Gamage and Prof. Rohini De A. Seneviratne Salt has been a highly valued commodity for centuries. In the 14th century, in certain markets [...]

The Sundaytimes Sri Lanka

Shake that salt habit

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March 11-17 is World Salt Awareness Week | After a century of study experts agree that there is direct link between high levels of sodium and high blood pressure

By Dr. Anuji Gamage and Prof. Rohini De A. Seneviratne

Salt has been a highly valued commodity for centuries. In the 14th century, in certain markets in North Africa salt was traded for its weight in gold! Salt has been taxed, monopolised, treasured and fought over for thousands of years. It is used to add flavour to food, and as a preservative.Also known as sodium chloride, salt is made up of 40% sodium and 60% chloride. Sodium, the main component of salt is a vital nutrient -our bodies will not be able to survive without sodium. The human body is unable to produce its own sodium. It facilitates many functions in the human body such as, the controlling of water in our body, maintaining the body pH, transmitting nerve signals, and helping in muscular contractions.

Although it is a necessary component/ nutrient, a growing body of evidence shows that we consume far more salt than our body can handle.

The salt hypothesis

High dietary sodium intake is a known risk factor in the development of high blood pressure. The relationship between salt and blood pressure has been studied for more than a century.

Many experts agree that there is a direct link between excess salt in the diet and high blood pressure. “Blood pressure is the biggest cause of death in the world and salt is the most important thing that makes it rise,” says Graham McGregor, a professor of cardiovascular medicine at the London based Wolfsan Institute of Preventive Medicine and chairman of the influential World Action of Salt and Health (WASH) lobby group. He adds that cutting back on salt gives a direct beneficial effect on the biggest cause of death in the world.

An average 5 mm Hg reduction in blood pressure will be achieved for every 6g/day reduction in salt (7 mm Hg in hypertensives, 4mm Hg in normotensives). On this basis, it can be estimated that a population-wide reduction of 6 g/day will result in a 24% reduction of deaths due to stroke and 18% reduction in deaths from coronary heart disease or avoidance of some 2.5million deaths worldwide every year.

How to interpret yourblood pressure results

The INTERSALT study was a standard epidemiological study that showed an association between dietary salt, measured by urinary excretion and blood pressure. The study was based on a sample of 10, 079 men and women age 20--59, sampled from 52 populations spread across the world. The results were disputed by the Salt Institute (the salt producers’ trade organisation), as this study showed a clear link between salt and blood pressure, although the effect upon individuals varied greatly. When the researchers compared the higher blood pressure levels against the participant’s age, a pattern began to emerge. While young adults were generally less sensitive, the middle-aged and older adults were more likely to have high blood pressure due to high salt intake.

The authors concluded that INTERSALT results, agreed with findings from other diverse studies, including data from clinical observations, therapeutic interventions, randomised controlled trials, animal experiments, physiologic investigations, evolutionary biology research, anthropologic research, and epidemiologic studies, and support the judgement that habitual high salt intake is one of the quantitatively important, preventable mass exposures causing the unfavourable population-wide blood pressure pattern that is a major risk factor for the current epidemic of cardiovascular disease.

Other noteworthy reviews of the ‘Salt hypothesis’ include the WHO report released in 2007 which was titled ‘Reducing Salt Intake in Populations’. He also states that ‘totality of evidence for reducing salt is stronger than for any other non-pharmacological treatment’.

Another study published in the Journal of Hypertension, by Graham. A. Macgregor concludes that reducing salt intake would make people drink fewer amounts of soft drinks. How? More salt makes us thirsty so we buy more beverages.

Sources of sodium

More than three quarters of salt intake is derived from processed foods, 12% from naturally occuring sources, while11% is added during cooking and eating e.g., habitual adding of salt during preparation of rice and curry in Sri Lanka.

Content in processed foods varies according to the particular preparation method/ recipes. The major source of dietary salt is therefore from processed food. With urbanisation and rapid development the typical Sri Lankan lifestyle is drastically changing; opting for fast foods, restaurant food, instead of the healthy home made diet is a common scenario.

This is important from the public health perspective. Will reduction in salt intake at the population level reduce the incidence of high blood pressure? Judgement on this issue forms the basis of policy recommendations, which has to include action on quality control and labelling of processed foods. Hence commercial food supply is a principle source to be addressed.

How much is too much?

According to WHO recommendation, adults are advised to consume no more than 5g per day. This is equivalent to 1 teaspoon of salt. The actual consumption however, is much more. In many of the countries the average intake of salt is about 10g/ day. A study that has been conducted in Sri Lanka has reported the average intake of salt to be about 8.7g/day. In communities where the average daily salt intake is 3g/day or less, the average blood pressure is lower and shows little tendency to rise with age. Studies have proven that reducing salt intake to 6g/day would lead to 13% reduction in stroke and 10% reduction in ischaemic heart disease. This is a challenging but achievable goal.

How?

  • Reduce eating fast foods, processed foods and frequency of eating out ( as this is the major source of high salt and excessive salt).
  • Read food labels! Some labels provide both salt and sodium content and opt for those lower in salt.
  • f you’re checking labels, here’s the guide- based on 100mg
  • A lot of salt = 1.25g salt- would be labelled as red on the traffic light labelling system
  • A little salt =0.25g salt-would be labelled as green on a traffic light labelling system
  • Anything in-between these figures indicates a moderate amount of salt
  • Opt for fresh fruits and vegetable when snacking
  • Cut back from salt gradually over a period of weeks and you will find that your taste buds don’t miss the salty flavour in foods. In fact you would find that the salt added is too much even if it is just a little. Taste buds do adapt!

Reducing salt can reduce blood pressure. In trials that have been conducted, it has been shown that reducing from high salt (8.7g) to intermediate salt (5.8g) consumption can reduce systolic blood pressure by 2.1 mmHg. If consumption is further reduced from intermediate to low salt (3g) consumption per day an additional 4.6mmHg would be reduced of the systolic blood pressure.

The evidence is abundant, let’s start acting now.

(Dr. Anuji Gamage is Registrar in Community Medicine, Nutrition Division, Ministry of Health. and Prof. Rohini De A. Seneviratne is Senior Professor in Community Medicine and Head, Department of Community Medicine, Faculty of Medicine, University of Colombo)




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