The salt of the question

Salt has been the basis of life for a long time. It once served as a type of money, roads were built to transport it, and cities sprang up in places of salt production and trade. And of course, people ate it. Today, it continues to be used all over the world.

It's hard to believe that a product that has been so firmly rooted in human life for centuries and civilizations can be harmful to the body. As seasoning manufacturers around the world tell us, salt consumption is associated with a risk of high blood pressure, which, in turn, is fraught with heart disease.

How much salt do we consume? How much harm does salt do to your health? The results of the research conducted by the NUTRICODE expert group, published in the New England Journal of Medicine (NEJM), make you think twice before reaching for the salt shaker.

In 2010, the average daily sodium intake per person was 3.95 g, which significantly exceeded the recommendation of the World Health Organization, which is 2 g per day. What are the consequences? According to the authors, almost one in ten deaths from cardiovascular diseases in 2010 could be caused by excessive sodium intake. That's about 1.65 million deaths worldwide. Moreover, over 40% of these deaths were premature (i.e., before the age of 70).

The highest mortality rate was observed in Central Asia, as well as Eastern and Central Europe. Of the individual countries, the highest mortality rate was observed in Georgia (1967 deaths per 1 million adults per year), and the lowest in Kenya (4 deaths per 1 million adults per year).

The authors also found that lower sodium intake is associated with lower blood pressure. For example, in a 50-year-old Caucasian with normal blood pressure, a decrease in salt intake by 2.3 g per day lowered systolic blood pressure by 3.74 mmHg. The exact magnitude of the effect varied depending on age and race, and the decrease was more pronounced in the elderly (compared with the young), Negroids (compared with Caucasians) and people suffering from hypertension (compared to healthy people).

Does this mean that low sodium intake will make you healthier? Not necessarily, according to two other articles published in the New England Journal of Medicine. In one study (PURE), urinary sodium excretion in 24 hours was calculated in more than 100,000 adults from 18 countries (an approximate indicator of sodium intake). Then the correlation with blood pressure was established.

The researchers found a non-linear relationship. In people who consumed a lot of sodium (which in this study was over 5 grams per day), each additional gram of sodium was associated with a sharp increase in blood pressure (2.58 mmHg per gram). However, in people with low sodium intake (less than 3 grams per day), the association with blood pressure was not statistically significant (0.74 mmHg per gram; P=0.19). It is noteworthy that only 10% of the study participants fell into the low-sodium category, and only 4% had sodium excretion levels consistent with current U.S. guidelines for sodium intake.

Based on these results, Dr. Suzanne Oparil of the University of Alabama at Birmingham suggests in an editorial that recommending a low-sodium diet won't do much good. She writes: "According to the results of the study, the authors concluded that only a very small proportion of the world's population adheres to a low-sodium diet and that sodium intake in these people is not associated with blood pressure. This casts doubt on the feasibility and benefit of reducing sodium in the diet as a strategy for lowering blood pressure at the population level. An alternative recommendation to stick to a high-quality diet rich in potassium may have more health benefits, including lowering blood pressure, than aggressively reducing sodium intake alone," Oparil writes.

"Sodium and chlorine ions perform diverse functions in the body. Sodium maintains normal osmotic pressure, regulates the movement of water, and normalizes the acid-base state. Excess sodium leads to water retention in the body, helps to increase vascular tone, and an excess of chlorine anions acts similarly.

The data from the Birmingham study are interesting, of course, but there are still many more factors involved in blood pressure regulation.

Answering the question of whether to salt or not, it should be borne in mind that, firstly, most foods already contain sodium chloride, and adding salt to food can lead to excessive daily intake and, as a result, increased reserves of sodium and chlorine ions in the body. Secondly, from the point of view of physiology, there is still more data on the harm of excessive salt intake, so the recommendation of moderation in its consumption in combination with a rational and balanced diet with a sufficient amount of another major cation, potassium, looks logical and reasonable."