What is salt? Common salt, or table salt, is one of the main condiments we use every day: It is a mineral; It has 40% sodium and 60% chlorine; 5 g of salt (or 1 level teaspoon) is approximately 2 grams of sodium; Sodium is an electrolyte with irreplaceable functions in the body, but in excess it can be a source of disease. Some history, numbers and recommendations For about 5 million years, man and his ancestors only ingested the salt that food naturally contained, that is about 0.5 grams per day. With the discovery of the properties of salt in curing and preserving food, its exploitation became an activity of great importance, and salt became a common food ingredient. And salt intake multiplied almost by 20. In the 19 th century, in Europe, it reached 18 grams per day; Current worldwide intake levels are around 9-12 grams per day. According to the World Health Organization, in 2017 excess salt was responsible for about 3 million deaths worldwide and is one of the main food-related health risk factors. The salt intake recommended by the World Health Organization for the prevention of cardiovascular disease is less than 5 grams per day or 2 grams of sodium . In 2012, the Portuguese consumed an average of 10.7 grams of salt per day, more than twice the recommended amount. Where does the salt in our food come from? With some variations between regions and countries, eating habits and lifestyles, the origin of salt in our diet comes from: About 75% of processed foods and meals prepared outside the home; 15%-20% results from what we use at home when cooking or add when eating. We add salt to food when we cook it because this condiment enhances the flavor. In fact, the regular consumption of salt inhibits the detection of the taste of food by the taste buds and, therefore, we add salt so that food do not become tasteless, and we continue to feel it tasty. In the case of processed foods, the addition of salt is also related to flavor and, depending on the product, also to conservation. In these foods, the amounts added are sometimes higher than desired, which can lead to an increase in the weight of packaged products and also in the need for fluid intake. What is the role of salt in our organism? Salt present in foods and drinks is one of the main body sources of sodium. And sodium is one of the most important electrolytes in the body, it has numerous irreplaceable functions , for example in: Contraction of skeletal muscle and cardiac muscle; Formation and conduction of nerve impulses; Maintaining the water balance and in the hydration and nutrition of the cells; Regulation of blood volume; Immunity and fight against diseases. However, the amount of sodium (and salt) we need to ingest to meet needs and for all these tasks to be carried out successfully is very small. What happens if we eat salt (and we have sodium) in excess? Our organism must have an optimum and stable sodium concentration. When faced with excess salt, he tries to compensate for it using various mechanisms: Increases sodium elimination mainly through the kidneys (in the urine), and also through the skin and intestines; Deposit it in places where it behaves like an inert substance. However, the continuous intake of excess salt causes these compensation mechanisms to stop working properly and even to fail, with multiple associated health problems, for example: Increased blood pressure It is more severe in patients with sensitivity to salt, particularly in elderly patients and diabetics. The increase in blood pressure is due to increased blood volume, damage to vessels caused by salt accumulated on the inner surface of their walls (endothelium) and vasoconstriction mediated by activation of the hormonal system and autonomic nervous system. Cardiovascular disease regardless of increased blood pressure It is due to direct injury of arteries, cardiac muscle hypertrophy and fibrosis mediated by hormonal activation (aldosterone). Kidney disease It is due to direct damage to the small vessels of the renal glomeruli where sodium filtration takes place, with a decrease in the clearance function and loss of protein in the urine. Osteoporosis It is due to bone demineralization because calcium is dragged along with sodium during its urinary excretion. Kidney stones It is due to the increased excretion of calcium in the urine that forms the calculi, a process that also directly damages the kidneys. Decreased muscle mas To compensate for excess salt and try to maintain an adequate concentration, water contained in the muscles is used, which contributes to its degradation. Increased susceptibility to diabetes and obesity It is due to decreased muscle mass and increased insulin resistance. Promotion of inflammatory states It is due to the inhibition of the production of anti-inflammatory substances, such as nitric oxide. Autoimmune diseases Due to exaggerated activation of the immune system with production of abnormal cytokines that activate macrophages and T lymphocytes. Skin aging It is due to sodium accumulation mediated by inflammatory and autoimmunity phenomena. Gastric tumors By direct injury to the gastric mucosa. How are recommendations to reduce salt intake justified? The scientific evidence on the link between excessive salt consumption and various diseases, among which cardiovascular diseases stand out, is numerous and not new. Among this, more than 30 observational studies and about a dozen randomized studies, which have greater scientific robustness, revealed that the decrease in sodium intake in hypertensive or pre-hypertensive patients translates into a decrease in overall mortality and not just mortality due to cardiovascular cause. This is the case, for example, of the TOHP1, TOHP 2 and SSaSS (salt substitute and stroke study) studies. And now that you know the most important thing about the effects of excess salt, start reducing it in your diet! Sources He F, Tan M, Ma Y, Graham A. Salt reduction to prevent hypertension and cardiovascular disease . J Am Coll Cardiol 2020;75:632-47. Ma Z, Hummel SL, Sun N, Chen Y. From salt to hypertension, what is missed? J Clin Hypertens 2021;23:2033-41. Robinson AT, Edwards DG, Farquhar WB. The influence of dietary salt beyond blood pressure. Curr Hypertens Rep 2019;21:42. World Health Organization. Salt intake . Author : Lígia Mendes Meet the cardiology clinical team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
