This is known, Rhonda Patrick talks about it on Joe Rogan (I can hear you groaning).
What confuses me is that this ties new research to old, outdated research (the old wisdom that salt leads to high blood pressure). No sources, but latest studies show excess salt is not harmful in healthy people.
I checked one of the papers they refer to [0] and... well, they fed mice (not humans) a diet with an 8- to 16-fold increase in salt.
As with all nutrients, there is an optimal intake range, and anything below or above that is by definition sub-optimal. In humans, the optimum for sodium intake per day seems to be well above dietary recommendations, but also well below 16 times the amounts described in those recommendations.
Also, it is worth noting that the first sentence in the linked paper is again repeating the same unreasoned "we all know salt is bad" dogma. Diets high in salt in the western world are also high in many, many other things that are bad for you. Epidemiology is useless to derive new information, it only works to establish future work or to deny previous hypotheses.
[0]: http://sci-hub.tw/https://www.nature.com/articles/s41593-017...
Is there some underlying assumption that those researches are idiots and didn't know all that?
The logical interpretation is that they gave 8- to 16-fold increase in salt purposefully, because they cared to see whether there are any specific effects mediated through salt. In over words, they want to put the effects on full blast to magnify responses and be able to see some novel connection, not to see how a mouse cops with mild over-consumption of salt.
Specifically, the article says that they found it resulted "in increased vulnerability of the brain to autoimmunity", which one wouldn't expect from sub-optimal salt intake alone. This is not some rehash of "very high salt = blood pressure, duh!".
The issue is reporting of results to the public. Someone feeds mice a ridiculous amount of salt and notices they have some health issues. Let's assume for an instant that this is somehow useful for some reason (I mean, salt poisoining has been known for millenia and people actually commit suicide by drinking saturated salt solutions). Even in that case, journalists are still distilling the whole thing into "more salt is bad", which is what the average person will understand. The general public doesn't read scientific literature with a critical thinking mindset, if at all.
Sodium intake is actually regulated by the body, just like protein. Your body demands more salt when it needs it. Which means that around 3.7 grams might actually be the optimal amount of sodium intake.
There are many studies showing that the standard recommendation for reducing the salt intake is bullshit. Not only that, but reduced salt intake is linked to obesity and sugar cravings.
Also before refrigerators, like in the 19th century, people consumed a lot more sodium because salt was the primary way to preserve food, especially meat. All modern chronic diseases were rare back then ... and yes, heart disease was harder to diagnose, but improvements in technology can't explain it fully, plus we are also talking of diabetes and cancer.
For skeptics, I recommend reading "The Salt Fix" which provides a good overview of the history and of various studies: http://thesaltfix.com/
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I'm not saying that healthcare professionals are idiots.
The problem is that healthcare is reductionist. Studies that properly use the scientific method don't lie, but the problem is that people often reach the wrong conclusions.
It's like in that fable in which a group of blind people are told to feel and describe an elephant, only in real life some of the blind people have more political clout than others.
Someone then probably tried to prove this by checking whether dietary salt intake leads to hypertension. However, medical and nutritional science are very limited in the ways they can conduct research. So they probably did an epidemiological study and saw that populations with hypertension also had a high dietary salt intake. Proof! Except... well, no.
Our kidneys are perfectly capable of balancing this out as long as we don't ask too much of them. More salt in your food than you need? More sodium in your pee. Less salt in your food than you need? Well, you're screwed.
Edit: Sorry for being unable to provide a direct answer to your question, but I felt compelled to reply.
Edit 2: After a search in Google Scholar, the earliest study I could find is from 1950 [0]. They studied the link between salt and hypertension in rats by replacing their drinking water with 2% salt solutions and measuring their blood pressure. It seems to me that all non-epidemiological studies are useless extremes... With no "clean" water (all water intake was hypertonic) the kidneys can't really dispose of much.
[0]: http://sci-hub.tw/https://journals.sagepub.com/doi/abs/10.31...
Edit 3: The actual paper recognises in the discussion (with citations) that it is impossible to cause hypertension in rats without artificially controlling all their water intake. Wow. Even if all water is salted, as long as it's iso- or hypotonic there is no hypertension.
Regrettably I can't find the source.
It's like with cholesterol, i.e. the claim that eating saturated fat can increase LDL particles in your bloodstream (it can), but to jump from there to claiming that increased LDL causes heart disease is a stretch, because LDL is just a transport mechanism and naturally, it depends on what it transports.
People are inclined to search for easy solutions. But unfortunately nothing is easy about our metabolism.
The stories that get retold, aren't the ones that are true, but often the ones that are simplest to tell.
Saying its not harmful in healthy people (depending on how you define healthy) is a pretty ignorant thing to say.
In any case, there is this: https://www.acsh.org/news/2018/08/10/spoonful-salt-makes-blo...
Which suggests that salt intake does raise blood pressure slightly, but it's a very small effect and does not measurably impact actual cardiovascular outcomes.
Even specialists disagree, leaving you with the choice of which you trust more. They can't all be right.
That leads to confusion and general mistrust for doctors. If skilled doctor doesn't know what he does, how can I? If I don't know better than doctor, how can I know who gives better advice? How to find that good advice?
I'm an environmental studies major. I think it's complicated. I tend to not bother to argue it. My doubts are not some kind of definitive proof that the assertions of others are wrong. I mostly think it's not worth debating at this point in time.
There are plenty of negative changes that are well documented, such as species going extinct, species on the Endangered Species list, etc. We don't really need to prove global warming one way or the other to know that we need to make some changes in a big way and very soon because the course we are on is clearly a crash course.
The science of climate change is also multi-level, gradually converging on details with more and more sophisticated models, but the core of it rests on the absorbtion and re-emission spectra of CO2 and water vapor, which is some fairly simple long-settled experimental chemistry.
(Wikipedia traces it to this fascinating little paper by Eunice Foote in AAAS in 1856! https://books.google.co.uk/books?id=6xhFAQAAMAAJ&pg=PA382&re... )
For example, a new type of food may become quite popular over the course of like five to ten years. In that time millions upon millions of people will undergo a change in their gut flora from eating that food--even if only on occasion!
Who TF knows what the long term impact of such an evolutionary change could be? 90% of the time it's probably nothing but 10% of the people might develop IBS later in life because their gut bacteria suddenly evolved in such a way as to throw off the "balance of power" (as it were... The many zillions of gut bacteria are constantly at war with each other to process food faster and more efficiently).
The issue with nutritional science is that you essentially have to rely on humans accurately taking some prescribed action and self-reporting it truthfully. As far as data points go, that is as flimsy as it gets.
Isn't the vast majority of climate change skepticism just political ideology anyway? I really haven't met too many people that were interested in rebutting the science.
Since "the latest nutritional studies" are a dime a dozen, and one says one thing, another says the opposite, it's wise to ignore them altogether until they are grown more and established into a concrete set of suggestions.
I'd ignore anything that hasn't reach the level of "nutrition 101" in a university course, and is still on "just published on a peer reviewed journal" level.
If you have a specific medical condition, a best practice is to start a folder of some sort and collect good information there and try to understand it yourself. Another good thing to do is keep a health journal where you track, to some degree or other, specific metrics pertinent to your specific condition.
What I have concluded is that a lot of advice of that sort is over-simplifying a complex biological process. Figuring out what makes sense in terms of diet involves fleshing out your own mental models for the pathology of the condition in question.
This is bullshit. "Most doctors" know very little about the electromechanical processes involved in a keystroke but they still know it results in a letter appearing on the screen.
A doctor's job is to keep you alive and to a lesser extent, healthy. They are not in the fitness businesses but they sure know that fit people have less health problems. Problems that they ultimately get stuck treating.
Do they know the chemical processes at work (in detail) in the brain when you eat something? Probably not... Not unless they're a gastroenterologist/neurologist. But do they know that eating loads of sugar every day can lead to Type II diabetes? They sure do! I'd even go so far as to say, "Doctors know quite a lot more than most people" about such things!
They also know loads of things about salt! Ask any psychiatrist about the effects of high salt intake on various mental conditions (and their respective treatments). Ask any pediatrician what would happen if you fed a tablespoon of salt to a baby. Ask a dermatologist about salt in general (wow, take a seat and be prepared for a lecture).
When you say "nutrition was more effective in treatment/prevention than anything prescribed and stating 1 focused on that" I call bullshit. Its just a known fact that diet changes can alleviate issues so its pretty much a given but its not going to alleviate the issues right away (in most instances) which is the doctors primary concern. So they often prescribed medicine to do just this.
If you need a doctor to explicitly mention to you that good nutrition will improve your health, then I'd suggest being a little more perceptive. But case in point, every doctor I've met has recommended diet changes to alleviate my symptoms.
huh? the point was made about their in depth understanding of impact of specific nutrition. not that "good diet is important" generality. and I am being "a little more perceptive" by doing a decade of my own research. not sure why that comment was necessary or what it has to do with my point
this is a common truism that may or may not be beneficial to any one individual. it has nothing to do with understanding of nutrition as pertaining to treating specific health issues.
it's like saying, "exercise and sleep good". while this is true in most cases, has nothing to do with original point "Most doctors know very little about what food does to the body."
But doctors don't get "stuck" treating health issues! On the contrary, that's how they get paid! Doctors' jobs, unfortunately, have perverse compensation structures which disincentivize their helping patients reach maximum healthiness. They get paid to keep you alive, yes. But they get paid much more if you remain in a state of imperfect health -- and thus remain a patient, requiring paid treatment -- than if you happily stay fit and only visit for routine checkups.
Some cultures (eg the proverbial village doctor in some parts of Asia) resolved this conflict of interest by having members of the community pay the doctor only while they're healthy, but pay nothing when faced with illness. Interesting to think what such a model might look like in modern western civ.
From my observations, it isn't.
> Doctors know quite a lot more than most people
In general, I don't think most doctors do.
Saying they know "very little about what food does to the body" might be stretching it a bit far. It's more like:
_most_ people know very little and doctors, on the whole, appear to know a little more than most people.
Having said that, there are doctors who know their stuff. I just don't think it's fair to say this characterizes most doctors
I have a form of cystic fibrosis. It is standard practice for CF clinics to have a dietitian on staff. Last I checked, they recommended a "high fat, high calorie, high salt" diet for CF. In line with that, they straight up recommend you eat junk food.
I'm currently drug free, which is supposed to be impossible. I achieved that in part by focusing on improving my nutritional status. Instead of eating a high calorie, junk food diet, I got very picky about food quality and nutritional value.
So that's where I'm coming from. I'm a former homemaker. If me reading up a bit on nutrition and food chemistry and applying it to my life can get such dramatically better results than conventional wisdom for my condition, it seems to me the bar for what doctors need to know about food and health is set pretty low.
Obviously, they could tell people that this is the reason and treat us like adults, but they don't seem to want to.