Population-based salt intake survey to support the national salt reduction programme for Malaysia

Cardiovascular disease including strokes, heart attacks and heart failure, is the leading cause of death and disability in Malaysia and worldwide. Hypertension is an important risk factor for cardiovascular disease, responsible for over 60% of strokes and almost 50% of coronary heart disease. High salt intake is the major cause of hypertension, accounting for about half of the disease burden attributable to blood pressure. Reducing salt intake to the World Health Organisation recommended level of 5 gram/day could prevent approximately 1.65 million cardiovascular deaths per year globally. There is also evidence that a reduction in salt intake may have many other beneficial effects on health. For example, a lower salt intake is associated with a reduced risk of stomach cancer, related to a lower risk of obesity directly or indirectly through a reduction in soft drink consumption, and associated with a reduced risk of kidney diseases and osteoporosis. Indeed, salt reduction is one of the most cost-effective public health policies to reduce non-communicable diseases. The World Health Organisation has recommended salt reduction as one of the top three priority actions to tackle the global non-communicable disease crisis.

In Malaysia, the prevalence of hypertension is high with approximately one third of the adult population having hypertension in 2011. This figure continues to rise. It is estimated that 7.6 million adults would have hypertension by 2020. Salt intake in Malaysia is likely to be very high. The Ministry of Health Malaysia started a salt reduction initiative in 2010. However, the progress has been very slow and there is still lack of key contemporary data upon which to formulate policy and engage key stakeholders. We propose to carry out a cross-sectional study to determine the level of salt intake among the Malaysian adult population using the gold standard method, i.e. 24h urine collection. Additionally, we will assess the main sources of salt in the diet using food frequency questionnaire, and assess the knowledge, attitude and practice towards dietary salt among the Malaysian adult population by completing a standardised questionnaire.

Our study will provide valuable data which are urgently needed for the development and effective implementation of a national salt reduction programme in Malaysia. This will lower salt intake across the whole population and thereby prevent many thousands of unnecessary deaths from strokes, heart attacks and heart failure each year, and also lead to major cost-savings to individuals, their families and the health services.

Although our study will be carried out in Malaysia, the research findings and the evidence-based salt reduction strategy developed in our study could potentially be generalisable to many other developing countries, particularly South East Asia. A reduction in salt intake, even by a small amount, across the whole population around the world will have enormous benefits in reducing the huge burden attributable to chronic non-communicable diseases.

We will carry out a cross-sectional study in 1100 adults aged over 18 years. The participants will be randomly selected by a multi-stage stratified cluster sampling of Living Quarters (LQs) throughout Malaysia.

The data collection will include
(1) Complete a general questionnaire on basic demographics, disease history and medication use.
(2) Complete a questionnaire which assesses knowledge, attitude and practice about salt.
(3) Complete the food frequency questionnaire (FFQ). Trained dietitian or nutritionist will interview the participants using a pre-tested and validated FFQ including 94 food items.
(4) Do a brief physical examination including blood pressure, body weight, height, waist and hip circumference using a standardised protocol.
(5) Complete one 24h urine collection which is the gold standard method in determining the level of dietary salt intake. All participants will be given both oral and printed instructions on how to accurately collect 24-h urine. We will measure urine volume, sodium, potassium and creatinine. Ion-selective electrode method will be used for sodium and potassium analysis and Jaffe method for creatinine. Twenty-four hour urinary creatinine together with urine volume will be used to determine if the collection is likely to be complete.

The primary outcome of the study is salt intake as measured by 24-hour urinary sodium excretion. The secondary outcomes are the main sources of salt in the diet, knowledge levels, attitude and current practices relating to salt.

Humans only need a very small amount of salt from the diet, i.e. less than 1 gram per day to maintain normal physiological function. However, the vast majority of the population including children eat far more salt than they need (on average most adult populations in the world eat 9-12 times that level). This high salt intake has many harmful effects on health.

Our project will provide new evidence that will lead to a reduction in population salt intake. Almost everyone stands to benefit from a reduction in salt intake because almost everyone eats far more salt than they require. The immediate benefit from a reduction in salt intake is to lower blood pressure. For adults, this will have an immediate and significant benefit on reducing the risk of suffering a stroke, heart attack or heart failure. For children, a lower salt intake will prevent the development of hypertension and thereby cardiovascular disease when they grow older. From a population viewpoint, even a modest reduction in salt intake across the whole population will have a large impact on reducing the appalling burden of cardiovascular disease in the population. Furthermore, a reduction in salt intake may also have other beneficial effects on health, for example, salt reduction may help reduce obesity and lower the risk of stomach cancer, kidney disease and osteoporosis.

A reduction in salt intake not only saves lives, but also saves money to individuals and the health service. A paper in the Lancet demonstrates that a 15% reduction in population salt intake could avert 8.5 million cardiovascular deaths over 10 years in 23 developing countries and result in major cost-savings to individuals, their families and the health services. Indeed, such a modest reduction in salt intake is more, or at the very least just, as cost-effective as tobacco control in terms of reducing cardiovascular disease, the leading cause of death and disability in Malaysia and worldwide.