Disclaimer: First let me assure you, I am not a medical or health professional of any kind, do not play one on TV nor claim to be one at parties or on dates - nor do I have licenses, certifications or advanced degrees of any kind - therefore nothing I write here is or can be construed as medical advice.
I am also free from any conflict of interest from affiliation, attachment
or involvement with any industrial, government or academic institution or
organization. What I have to say here is gleaned from careful and critical
reading of publicly available material.
Sodium & Salt
A teaspoon of regular table salt weighs roughly 6 grams (6,000 mg) which is about 40% sodium by weight, or 2,400 mg sodium. The average American consumes between 3,600 and 4,800 mg of sodium per day, or 1.5 to 2 teaspoons (American Heart Association numbers). The current U.S. government Centers for Disease Control (CDC) recommended range is between 1,500 and 2,300 mg. The American Heart Association says 1,500 mg or less. Anything much below 500 mg is considered immediately dangerous, but maximums are highly variable, with some people reported able to handle 30,000 mg.Salt & Cardiac Health
Listening to public policy proclamations, the media and do-gooders (one of the most dangerous elements in our society) you could easily conclude that the evidence is in and uncontroversial - salt consumption is very bad and will cause heart attacks and stroke. Salt consumption should be reduced by government mandate.
That conclusion would be quite premature. Most of the policy outcry is based on a single study that was seriously defective in design. Many more recent scientific and demographic studies do not support the conclusions of that study and some researchers now believe it was the accompanying radical reduction in sugar, not salt, that improved heart health.
A recent study involving over 275,000 people was published in the American Journal of Hypertension, published in March or April 2014, confirming and refining the results of previous studies. It found that that sodium consumption either above or below the "normal" range of 2,645 to 4,945 mg increased risk of both ACM (All-Causes Mortality) and CVD (Cardiovascular Mortality). It appears the AHA is, once again, providing recommendations detrimental to your health. Well, at least they are consistent.
Note that the AHA reports the average American currently consumes between 3,600 and 4,800 mg of sodium per day, which is entirely within the lowest mortality range. Most people in the entire world, regardless of diet or ethnicity, have been found to stay within the 2,645 to 4,945 mg per day range.
The Sodium Hypothesis: Let us start with the foundation of this charade, the "Sodium Hypothesis". This basis for much public policy and concerned outcry is simple: high blood pressure is associated with heart attacks and stroke. Salt is associated with high blood pressure. Therefore the general population should greatly reduce its salt consumption.
Note in particular the words "associated with". That is not the same as "causes". That high blood pressure causes heat attacks is not at all proven. It could be just another symptom of what causes them. If so, then reducing blood pressure will have little effect on the incidence of heart attacks and stroke.
Unfortunately, many studies have simply concentrated on that one thing, whether limiting salt intake significantly reduces blood pressure, and not on the actual health outcome - does reducing salt cut the risk of heart attacks and/or overall mortality?
To date, some significant studies that did aim to determine outcome have shown that low salt diets increase the incidence of heart attack and stroke (S1, S2, S3, S4, S7). A side result of one of the "low salt is detrimental" studies is that increased potassium intake reduced stroke.
Ignoring all of that, does reducing salt actually reduce blood pressure? Just as controversial - some evidence appears to show that it does so in only a small minority of people, not in the general population. Some researchers say most people have a very effective salt management system and would probably not show a significant blood pressure drop until their salt intake was very dangerously low.
Some promoters of lowering salt show a huge reduction in coronary problems from even a small decrease in salt consumption in the general population (S5). A lot of these numbers are derived from "complex computer models". That is absolutely laughable. Having many years intensive experience with computers, I firmly believe we should be highly suspicious of any such numbers. Billions spent on "complex computer models" run on advanced supercomputers and fed by thousands of ground stations and satellites cannot reliably predict if it's going to rain tomorrow. The human body is much more complex, variable and difficult to model than weather patterns. Our understanding of it is woefully inadequate to generate a reliable computer model, but experts can easily create a model that provides the answer they want to see.
Further, According to the U.S. Preventive Services Task Force "There is insufficient evidence that, for the general population, reducing dietary sodium intake or increasing dietary intake of iron, beta-carotene, or other antioxidants results in improved health outcomes." Canadian institutions have come to similar conclusions.
Gary Taubes prize winning article in the American Association for the Advancement of Science's magazine Science concludes, "After interviews with some 80 researchers, clinicians, and administrators around the world, it is safe to say that if ever there were a controversy over the interpretation of scientific data, this is it. After decades of intensive research, the apparent benefits of avoiding salt have only diminished. This suggests either that the true benefit has now been revealed and is indeed small or that it is non-existent and researchers believing they have detected such benefits have been deluded by the confounding of other variables."
Unfortunately, once the do-gooders have latched onto a defective theory, it takes on a life of its own and is almost impossible to correct. Careers now depend on it and businesses are now making money exploiting it. Unfortunately our formers of public policy pay a lot more attention to the shrieking do-gooders than they do to legitimate scientists. Most of them are politicians living by slogans and sound-bites and have little or no understanding of actual science, and care less.
But does public policy even matter? A 2009 study of 19,151 people in 33 countries shows salt consumption is remarkably uniform over cultures and diets - at between 2,700 and 4,900 mg per day (S2), pretty solidly within the "safe zone" from the new study referenced above (S7). Other studies tend to support this data. It seems the body's natural salt regulating system will effectively over-ride public policy.Salt & Stomach Cancer
A correlation has been found between high salt consumption and rates of stomach cancer. Studies have produced highly inconsistent results, but the results have been more consistent in China and Japan where large amounts of salt cured vegetables and seafood are consumed (S6), but even there inconsistency is the rule.Iodized Salt
Dietary iodine available in many inland and mountainous regions is insufficient for health. Low iodine results in swollen thyroid gland (goiter), stunted growth and severe mental retardation (cretinism) as well as less obvious problems. Government mandates to add small amounts of iodine compounds to table salt have nearly eliminated these problems in North America. Where this program has not been instituted, particularly the former Soviet Empire, the Near East and parts of Africa, these problems are still severe.
Today, even in North America, the success of this program is threatened by a number of factors:
All salt originates from the rocks and minerals of the Earth's crust, leached out by water and carried to oceans and closed lakes where it has been concentrated by evaporation. A major change in life on Earth happened when Calcium reached saturation in the oceans so living creatures could build shells and bones.
Natural salt is either evaporated from seawater, or mined from mineral deposits that are the buried remains of dried up salt lakes and inland seas. Sea salt varies somewhat from one location to another, but mined salt can vary quite a bit due to minerals migrated in and out of it by groundwater.
Opinion from dieticians seems to be this, "Salt is salt. It's just about all sodium chloride and there's too little of anything else to affect nutrition, though it does affect taste." I find it kind of difficult to believe that something in sufficient amount to affect taste is insufficient to affect trace mineral nutrition.
Recipes for salt fermenting vegetables, for instance Korean kimchee, specify natural sea salt (available cheaply and in bulk from Korean markets) because trace minerals are important for proper fermentation. Impact on health is debatable for the quantities of salt you should be eating.
Here are the dry matter compositions of table salt and typical sea salt so you can make your own evaluation:
Note that sea salt doesn't contain enough iodine to prevent Iodine deficiency, so some natural sea salt is iodized. Seafoods, including seaweed do concentrate sufficient iodine from seawater to be significant sources. Note that the high "Other" percentage in refined salt is usually anti-caking agents.
Note that salt labeled "Sea Salt" from major salt processors may have originated from seawater but is typically so refined it might as well be called table salt. The processors make more on the chemicals extracted from salt than they do on the salt itself, so thorough refining is to their advantage.Links