People who add salt to their table food are at higher risk of dying prematurely from any cause, according to a study of more than 500,000 people, published in European Heart Journal today (Monday).
Compared to those who never or rarely added salt, those who always added salt to their food had a 28% higher risk of dying prematurely. In the general population about three out of every hundred people aged 40-69 die prematurely. The increased risk of always adding salt to food, seen in the current study, suggests that one person in every hundred may die prematurely in this age group.
In addition, the study found a lower life expectancy among people who always added salt compared to those who never or rarely added salt. At age 50, life expectancy fell by 1.5 years and 2.28 years for women and men, respectively, who always added salt to their food compared to those who never or rarely did.
The researchers, led by Professor Lu Qi, of the Tulane University School of Public Health and Tropical Medicine, New Orleans, USA, say their findings have several public health implications.
“To my knowledge, our study is the first to assess the association between added salt in foods and premature death,” he said. “It provides new evidence to support recommendations to modify eating behaviors to improve health. Even a modest reduction in sodium intake, by adding less or no salt to table food, is likely to result in benefits significant health effects, especially when achieved in the general population”.
Estimating overall sodium intake is extremely difficult as many foods, especially pre-prepared and processed foods, have high levels of salt added before they reach the table. Studies that assess salt intake using urine tests often take only one urine test and thus do not necessarily reflect usual behavior. In addition, foods high in salt are often paired with foods rich in potassium, such as fruits and vegetables, which is good for us. . Potassium is known to protect against the risk of heart disease and metabolic diseases such as diabetes, while sodium increases the risk of diseases such as cancer, high blood pressure and stroke.
For these reasons, the researchers chose to look at whether or not people added salt to their meals at the table, regardless of any salt added during cooking.
“Adding salt to table foods is a common eating behavior that is directly related to an individual’s long-term preference for salty-tasting foods and habitual salt intake,” said Prof. Qi. “In the Western diet, added table salt accounts for 6-20% of total salt intake and provides a unique way to assess the association between habitual sodium intake and risk of death.”
The researchers analyzed data from 501,379 people who took part in the UK Biobank study. When they joined the study between 2006 and 2010, participants were asked, via a touchscreen questionnaire, whether they added salt to their foods (i) never/rarely, (ii) sometimes, (iii) usually, (iv) always , or (v) prefer not to answer. Those who chose not to answer were not included in the analysis. The researchers adjusted their analyzes to take into account factors that could affect the results, such as age, gender, race, deprivation, body mass index (BMI), smoking, alcohol intake, physical activity, diet and medical conditions such as diabetes, cancer and cardiovascular disease. They followed the participants for an average (median) of nine years. Premature death was defined as death before the age of 75 years.
In addition to finding that always adding salt to foods was associated with a higher risk of premature death from all causes and a reduction in life expectancy, the researchers found that these risks tended to be slightly reduced in people who consumed the highest amounts of fruit and fruits and vegetables, although these results were not statistically significant.
“We were not surprised by this discovery since fruits and vegetables are the main sources of potassium, which has protective effects and is associated with a lower risk of premature death,” said Prof. Qi.
He added: “Because our study is the first to report an association between added salt in foods and mortality, further studies are needed to confirm the findings before recommendations can be made.”
In an editorial to accompany the paper Professor Annika Rosengren, a senior researcher and professor of medicine at Sahlgrenska Academy, University of Gothenburg, Sweden, who was not involved in the research, writes that the net effect of a drastic reduction in salt intake for individuals remains controversial.
“Given the various indications that a very low sodium intake may not be beneficial, or even harmful, it is important to distinguish between recommendations on an individual basis and actions at the population level,” she writes.
She concludes: “Classical epidemiology argues that a greater net benefit is achieved by approaching the entire population (achieving a small effect in many people) than by targeting high-risk individuals (a large effect, but achieving only in a small number of people) The obvious and evidence-based strategy regarding the prevention of cardiovascular disease in individuals is early detection and treatment of hypertension, including lifestyle modifications, while community-wide salt reduction strategies will lower population average blood pressure levels, resulting in fewer people developing hypertension, needing treatment, and becoming ill. Not adding extra salt to the diet is unlikely to be harmful and may contribute to strategies for lower blood pressure levels in the population.”
A strong point of the study of Prof. Qi is the sheer number of people involved. It also has several limitations, which include: the possibility that added salt in food is indicative of an unhealthy lifestyle and lower socio-economic status, although the analyzes attempted to adjust for this; there was no information on the amount of salt added; the addition of salt may be related to total energy intake and combined with the intake of other foods; participation in the UK Biobank is voluntary and therefore the results are not representative of the general population, so further studies are needed to confirm the findings in other populations.
Prof. Qi and his colleagues will conduct further studies on the link between added salt in foods and various chronic diseases such as cardiovascular disease and diabetes. They also expect prospective clinical trials to test the effects of a reduction in salt intake on health outcomes.
 An example of a typical salty food that also contains vegetables is tacos, which are often filled with beans and vegetables.
 “Salt – the sweet spot?”, by Annika Rosengren. European Heart Journal. doi:10.1093/eurheartj/ehac336