You may have heard of the saying that "eating salt will raise blood pressure to unhealthy levels." This view can be traced back at least a century ago, and most of the views that "eating salt is harmful" come from this. It isn't as clear as the simple logic that makes you believe. Eating salt does indeed increase blood pressure, but it does not necessarily mean you should eat less salt.
Most experts believe that the first time salt and hypertension were linked together was in France in 1904.
There was a study at that time, two researchers followed up and surveyed six patients with hypertension for three weeks. They assigned subjects three different dietary regimens, possibly changing new recipes every week.
- Two liters of milk per day (almost no salt)
- Milk plus Protein , meat and eggs (with a small amount of salt)
- Milk plus two liters of broth (with a lot of salt)
Scientists who came up with these rare and cruel meal plans also measured the amount of salt in the subjects' urine every day to infer the amount of salt intake of the subjects. (It is much easier to estimate the sodium people consume based on excreted sodium than calculating the salt they eat.)
Researchers found that when people eat small amounts of salt, they excrete more sodium than they consume. However, when they eat a lot of salt, they consume more sodium than they excrete. And, when they eat more salt, their blood pressure is higher.
I hope I have taught you enough ways to judge studies, so you will certainly be suspicious of any research that has such a short duration and so few subjects. We don't even know whether this is a randomized trial or a blinded trial, nor whether scientists follow reasonable standards when selecting subjects—they also did not clearly state how "hypertension" is defined.
You won't want to pay too much attention to this kind of research, let alone formulate dietary health policies or make dietary decisions based on this.
However, in the next few decades, some people in the medical community began to treat hypertension by reducing their salt intake. This trend only emerged in the late 1940s, when a researcher named Walter Kempner at the time proved that he treated 500 patients with hypertension with a low-salt diet, but the diet consisted of only light rice and fruit, which was almost impossible to stick to. A lawsuit even accused Dr. Kempner of taking corporal punishment in order to make the subjects adhere to this diet.
Due to various reasons, this method of treating hypertension by reducing salt intake is not ideal.
First of all, if the solution requires us to convert into a lifestyle that seems very difficult to maintain (such as a boring diet composed of rice and fruit), we tend to try to find drugs with the same effect. salt balance is a good example.
The drug that prompts us to excrete salts, commonly known as diuretics, was widely used in the mid-1950s. doctors can more easily change patients’ salt balance without requiring them to adhere to a mad and unrealistic restrictive diet. However, these drugs may have obvious side effects, including electrolyte disorders , physical weakness, and even arrhythmia .
But ironically, actually has good evidence that salt intake can adversely affect patients with hypertension.
2014 published a study, namely "Prospective Urban and Rural Epidemiological Research" (PURE), which confirmed this. The researchers analyzed the sodium content in urine of more than 100,000 people in 18 countries and found that those who consumed more sodium had significantly higher blood pressure than those who consumed less sodium.The researchers also made a further analysis, which was also published in the same issue. analysis found that people who consume more than 7 grams of sodium per day had a much higher mortality rate than those who consumed 3 to 6 grams of sodium per day. People who consume a lot of sodium have a higher probability of heart attack, heart failure, and stroke .
Researchers in the field of health have discovered the same result again and again, and the conclusion is inevitable: People who eat too much salt should reduce the amount to avoid cardiovascular problems. Patients with hypertension should limit their sodium intake as much as possible.
But does this mean we should all avoid salt? No.
Many of us may eat too little salt, for example, Americans consume an average of 3.4 grams of sodium per day. In a 2014 study published in the New England Journal of Medicine, defines daily sodium intake of 3 to 6 grams as a "safe zone", while 3.4 grams falls into the lower value in this range. If the amount of sodium intake is much lower than this value, health may be affected. (Because there is a lower limit (zero) intake of salt, but there is no upper limit (people can eat a lot of salt), so more people who consume less than 3.4 grams of sodium per day are more than 3.4 grams of sodium. Remember this when others say "everyone eats too much salt".)
Of course, there is no consensus on how much salt is safe to eat. The US Food and Drug Administration believes that 3-6 grams of sodium intake per day is not small enough, and it is recommended to consume only 2.3 grams of sodium per day. WHO said that 2.0 grams of sodium should be consumed daily. American Heart Association goes a step further and recommends that we consume no more than 1.5 grams of sodium per day.
However, these numbers have no theoretical basis. In 2013, a committee of the American Institute of Medicine evaluated evidence on sodium intake worldwide. The Committee agreed that it was necessary to reduce excessive sodium intake, but they cautioned that there was no evidence to support a low-salt diet. They hope future research can point out the potential benefits of diets with daily sodium intake of 1.5 to 2.3 grams - a level advocated by other organizations.
2014 published in the New England Journal of Medicine solves this. In addition to tracking and investigating the health of people with high sodium diets, the study also compared their health with those with low sodium diets. researchers found that based on people who consume 3 to 6 grams of sodium per day, people who consume less than 3 grams per day are at a higher risk of death or cardiovascular events than those who consume more than 7 grams of sodium per day.
If the medical community had not known about this before, then this result would be shocking. However, similar research results have been found before. In 2011, the Journal of the American Medical Association published a study, which tracked and surveyed 3,681 people in about 10 years. Researchers also found that excessive intake of salt is related to hypertension. They also found that a low sodium diet was associated with increased mortality due to cardiovascular disease.
Obviously, consuming too much salt or too little salt can lead to heart attacks or strokes. So why do experts and organizations urge people to go from one extreme to another? Sadly, this is very common in the medical community, and we tend to apply the results of research targeting one group to everyone else.
This article is selected from "Is "bad" food really bad? 》
