Recently I was reading some of a new book called “The Salt Fix: Why the Experts Got it All Wrong and How Eating More Might Save Your Life”.
This contains the interesting claim that humans evolved on a diet high in salt. This is rather surprising as salt and sodium are generally considered to have been a rather scarce in human diets before the development of salt production technologies in the past few thousand years.
Reading this I thought I would delve into the evidence for this in a little more depth, which ended up with me fact-checking Chapter 2 of this book, which contains this claim. I thought that this would be interesting as firstly, evolutionary justifications are often used now in nutrition, and secondly, I had already seen statements from this part of the book quoted on social media.
As I don’t have the time or interest to review a whole book a subsection of Chapter 2 reviewed here is quoted in full from the subheading “Prehuman Primates” to the end of the subsection “The Case Is Clear” in Chapter 2. My comments are found between each quoted excerpt.
“Prehuman Primates
Even today, most people believe that prehuman primates (such as orangutans, monkeys, baboons, and macaques) subsisted mainly on fruit and terrestrial vegetation.”
This is not a great start as orangutans, monkeys, baboons, and macaques are not pre-human primates.
Most people believe that orangutans, monkeys, baboons, and macaques subsist mainly on fruit and terrestrial vegetation because they do.
“Thus, one group of scientists has insisted that our prehuman bodies evolved on a low-salt diet. But that is clearly not the case.”
This suggests that other groups of scientists have insisted we evolved on a high-salt diet, which does not seem to be the case.
“Millions of years ago, climate changes that featured intense dry seasons were thought to have forced nonhuman primates to seek out wetlands. 19 Their diet would have consisted of aquatic vegetation, with a sodium content five hundred times that of terrestrial plants. 20”
The only source I could find for the sodium content of aquatic plants was a paper from 1973 called “Sodium Dynamics in a Northern Ecosystem“, which examined the role of water plants in the diet of moose living on Isle Royale, Lake Superior. While floating aquatic pondweed can be a good source of sodium it is only really relevant if you are a herbivore like a moose that can eat large quantities of pond weed, in which case this can be a decent source of sodium. I could find no details for the African environments in which our early ancestors evolved.
While it may be true that aquatic plants can have a higher sodium content than terrestrial plants, this is still not very high because terrestrial plants have very low levels of sodium.
“This may also be when nonhuman primates started eating meat, which they would have first encountered when fish and aquatic invertebrates were trapped in aquatic vegetation – providing primates with the original seafood salad. 21”
I think catching fish is usually a little more difficult than this…
“Once these foods were “inadvertently” eaten, nonhuman primates probably got a taste for them and started seeking them out deliberately. Their first fish were thought to have been easier prey, such as catfish that were injured, washed ashore, or trapped in shallow ponds. (Catfish were plentiful where ancestral primates and early humans roamed, making this a plausible notion.) This dietary switch— toward consuming more fat and omega-3s— certainly makes sense for its potential to foster the development of a larger (more human-sized) brain. Dozens of nonhuman primates have been reported to eat fish and other aquatic fauna that would have supplied their diet with ample amounts of salt. 22”
While eating fish has occasionally been reported in nonhuman primates, this would not supply “ample amounts of salt” as fish do not contain high levels of salt. African catfish contain 406 mg of sodium per kilogram of raw catfish, which is not a high level.
A better explanation of the wetlands theory (not referenced here) is a book chapter called “The Case for Exploitation of Wetlands Environments and Foods by Pre-Sapiens Hominins“. This explains a new theory that wetlands were important to our earliest hominin ancestors and that fish may have been an early item on the menu.
But this does not imply that they were eating a high sodium diet.
“They would have encountered such things as shark eggs, shrimp, crabs, mussels, razor clams, snails, octopus, oysters and other shelled invertebrates, tree frogs, invertebrates in the river mud, snapping turtle eggs, water beetles, limpets, tadpoles, sand-hoppers, seal-lice, and earthworms. 23 These abounded at seashores and in swamps, freshwater and marine water, and other tropical and temperate locations. Based on this list, it’s obvious that the diet of prehuman primates (and thus early humans) would not have been low in salt; in fact, it could have been extremely high in salt.”
This rather diverse list contains a mixture of very different creatures and is copied out of context from reference [23].
- I suspect that our early hominin ancestors did not spend a lot of time eating water beetles, tadpoles, sand hoppers, or seal-lice.
- The shark eggs, shrimp, crabs, razor clams, octopus, and oysters are sea creatures that would not be found in the inland freshwater wetlands described in the theory described in the previous paragraph.
- The mussels, snails, tree frogs, and snapping turtle eggs are at least potential food sources for our early ancestors, but none of these is high in sodium.
No evidence is referenced that the creatures in this list available to early human ancestors are high in sodium (they don’t appear to be). The reference cited does not mention sodium. Therefore, it is not obvious that early human diets could have been high in sodium.
“The taste for fish and other aquatic creatures may have led these prehuman primates to begin deliberately trying to catch fish by hand and eventually using tools such as sticks, sand, and food to catch fish— which represented a huge leap forward in cognitive development. Think of that twist of fate: eating fish by happenstance may have enabled early primate brains to develop the intellect to actively catch fish through the use of tools. Exactly how they were able to obtain these salty creatures is more of a mystery, but it is thought that they used rocks to crack shells open and tapped on bamboo to find frogs living inside it. At least five other species, beyond orangutans, have been found to use tools to obtain fish and other salty aquatic prey. Thereafter, hominins – both modern and extinct humans – would have used primate fish-catching practices. 24″”
“…begin deliberately trying to catch fish by hand and eventually using tools such as sticks…”
“…and tapped on bamboo to find frogs living inside it.”
I’m not quite sure what to make of this. Have you ever tried catching fish with a stick or tapping on bamboo to find frogs? Additionally, neither fish nor frogs are high in sodium.
“Early Humans
Intriguingly, the emergence of tool-assisted fish catching in early Homo dates to around 2.4 million years ago. Primate fish-eating habits suggest that hominins would have also started eating aquatic plants first, then accidentally sampled the aquatic animals clinging to their nightly feeding, and, having acquired a taste for a newfound meat, eventually transitioned to catching fish and other aquatic prey. 25 Some researchers assert that an early human, Paranthropus boisei, and early Homo dug into wetlands to add vertebrates and invertebrates to what had previously been their predominantly plant-based diet. These aquatic animal foods yield plenty of salt and novel, high-quality nutrients, such as docosahexaenoic acid (DHA). Similar to how these essential fatty acids may have led to brain growth in prehuman primates, DHA allowed for the brain to increase in size in early humans. 26 The fact that DHA is important for the growth of the human brain creates the unavoidable suggestion that aquatic foods— and the hunger for salt that drew our ancestors to them— were an important player in how the human brain evolved into what it is today. 27 Terrestrial plants are low in DHA, which suggests that this transition to aquatic vegetation and prey was essential to increasing our brain size. 28 Imagine: our hunger for salt may have played a role in early humans’ great leap forward.”
Aquatic animal foods yield more sodium than land plants, but no reference is given here for how much this is. I have not been able to find any values for the sodium in aquatic animals in African wetlands where our early ancestors may have lived.
This is one theory of early human evolution that is presented as fact. The author attempts to link his theory of a high-salt diet without any evidence.
“Even early humans who lived far from the ocean’s brackish waters had this hunger for salt.”
I do not know how the author knows this.
“Data suggests that early humans roaming East Africa’s noncoastal regions between 1.4 and 2.4 million years ago may have consumed a diet extremely high in salt. An ancient ancestor to humans known as “Nutcracker Man” was said to have lived on large amounts of tiger nuts. 29 The fossils of this early human, discovered in 1959 in Tanzania, feature strong jaw muscles as well as wear and tear on molars, indicative of a diet high in tiger nuts.”
This is incorrect.
The “Nutcracker Man”, (Paranthropus boisei), was not a human ancestor.
A diet of tiger nuts is one theory to explain the highly specialized skull adapted for heavy chewing and the C4 carbon isotope ratios found in this species. However, reference [29] is actually a Daily Mail newspaper article… which I won’t link to.
While this branch of the hominin family is interesting it does not directly relate to the evolution of modern humans and our diet.
“Tiger nuts are extremely high in salt (up to 3,383 milligrams of sodium per 100 grams, the average amount of sodium we modern humans eat in an entire day). 30 Just a handful (3 ounces) of these nutlike tubers would have provided an entire day’s worth of sodium in today’s world.”
The single reference [30] cited gives a very high value (3,383 mg per 100 grams) for sodium in tiger nuts. Several other studies (not referenced in the book) show much lower levels of sodium in tiger nuts suggesting that reference [30] may not be representative of tiger nuts in general.
- Published figures report 37.6 mg of sodium per 100 grams in raw tiger nuts.
- Sodium varied from 235-245 mg per 100 grams of tiger nut flour.
- Sodium values of 12 mg per 100 grams in dried tiger nuts.
- Sodium values of 20 mg per 100 grams.
- Sodium values of 62 mg per 100 grams.
These suggest that tiger nuts are not necessarily a rich source of sodium and that the study cited in the book may be an outlier.
“Nutcracker Man did not live by nuts alone. He also survived on a diet largely composed of grasshoppers. A close relative of the grasshopper, the cricket contains a very good amount of sodium (about 152 milligrams of sodium per five crickets). 31”
This is incorrect.
The crickets tested, Acheta domesticus, weigh an average of around 0.4 grams and contain 152 mg of sodium in 100 grams of crickets. That means these crickets contain about 152 mg of sodium per 250 crickets, not per five crickets.
“Most likely, certain insects are so high in sodium because it allows them to move and fly faster and thus avoid being eaten by their brethren. 32 Scientists have observed that sodium deficiency can lead to cannibalism in insects (and probably other animals, too). 33 The theory goes that the animals instinctively know that salt is contained within blood, interstitial fluid, skin, muscle, and other parts of their bodies.”
Insects are not so high in sodium. As Reference [32] and [33] suggest, actually both are the same reference, that sodium deficiency is bad for insects and they will eat each other, but this is not really relevant to the discussion here as insects are rather different to humans.
“Not surprisingly, experts believe humans have been getting protein and micronutrients from wild insects for several millennia— and continue to do so to this day, particularly in parts of Africa, Asia, and Mexico. 34”
This reference [34] actually shows that insects are not high in sodium. Even for crickets, which had the highest sodium level of the insects tested, you would have to catch and eat more than 2 kg (4.4 pounds) of crickets each day (more than 5,000 crickets) to get close to the average sodium intake of Americans.
“”The Case Is Clear
From an evolutionary standpoint, evidence does not suggest that we evolved on a low-salt diet. Instead, much of our evolutionary theory seems to support the fact that we evolved on a high-salt diet. So where does this persistent misconception about our original diet come from?”
Is the case clear? No evidence has been presented so far to suggest that we evolved on a high-salt diet.
“The idea that our human ancestors consumed very little salt, generally less than 1,500 milligrams of sodium per day, is both old and current. 35 Some of the debate about evolutionary diet seems to stem from one influential paper on the topic, which was published in 1985 in the New England Journal of Medicine, one of the world’s most prestigious medical journals. The authors of this paper estimated that during the Paleolithic era (from about 2.6 million years ago until about 10,000 years ago), our intake of sodium was just 700 milligrams per day. 36 But this figure was based on the sodium content of select land animals (and only the sodium content of the meat) as well as land plants available to hunter-gatherers. This estimate does not include the sodium that would have been obtained from tiger nuts, insects, or aquatic vegetation or prey, nor does it include the other large stores of sodium found in animals besides the meat, such as that found in the skin, interstitial fluid, blood, and bone marrow (which we know hunter-gatherers did eat). We can’t forget that, aside from their meat, animals themselves (muscle, organs, viscera, skin, blood) are extremely good sources of salt.”
None of the evidence presented in this book questions the estimates made in 1985.
Muscle, organs, viscera, skin, blood) are not “extremely good” sources of salt. A diet based mainly on eating animals nose to tail can supply around 1,500 milligrams of sodium per day. But this is significantly lower than modern intakes of salt.
“For example, muscle contains approximately 1,150 milligrams of sodium per kilogram. Australian Aborigines would eat 2 to 3 kilograms of meat per sitting during a kill. 37 This is equal to 3,450 milligrams of sodium per day, the exact amount of sodium that current-day Americans consume (when they’re not straining to achieve the low-salt guidelines, that is!).”
This is incorrect. Meat does not contain that much sodium, but no reference is provided.
According to the USDA food database, 1 kilogram of “Beef, top sirloin, steak” contains 520 milligrams of sodium.
As another example, kangaroo meat contains between 40 and 60 milligrams of sodium per 100 grams. Eating 2-3 kilograms of kangaroo meat could contain 1000-1500 milligrams of sodium.
“Organs of animals are even higher in salt than meat: just 10 ounces of bison ribs (about one-quarter of a kilogram) provides 1,500 milligrams of sodium, the same amount in just 13.5 ounces of bison kidney or 2 pounds of bison liver. And remember, this doesn’t even include the salt that is found in the skin, interstitial fluid, blood, and bone marrow.”
This is incorrect. However, no reference is provided.
- 10 ounces of bison ribs contain 300 milligrams of sodium, not 1,500. Beef ribs seem to contain a bit less.
- 2 pounds of bison liver contains 882 milligrams of sodium, not 1,500 milligrams. This is equal to 276 milligrams in 10 ounces, similar to that found in meat.
- I could not find any measurement of bison kidney. But 100 grams of beef kidney contains 182 milligrams of sodium, more than in muscle meat but still not a lot.
This indicates that organ meats are not going to provide you with a lot of salt.
I could not find any measurement of sodium in the skin, bone marrow, or in “interstitial fluid” in animals, or any idea how you would go about eating interstitial fluid. If the author of the book has these figures he is not revealing them.
“Early humans probably got salt in other ways as well. Some would have also eaten soil, as is still done by Kikuyu women of Africa, who are known to make dishes from sodium-rich soil. 38”
If you read reference [38] it states that Kikuyu women of Africa did eat sodium rich soils, but that their diets were still very low in sodium despite this. To quote the reference:
“A nutritional study carried out a generation ago in Africa (Orr and Gilks, 1931) reports that Kikuyu women, especially during pregnancy and lactation, prepared a special dish making use of sodium-rich soils; men did not eat this. It is of interest to note that in spite of their regular daily utilization of edible earths, Kikuyu women obtained only between 0.88-1.56 grams of sodium per day, whereas males derived only 0.48 grams. Obviously, without the emphasis on sodium-rich soils, the Kikuyu diet would have been virtually devoid of sodium.”
“Our ancestors also likely had salt licks and drank rainwater, providing clear evidence that previous estimates of sodium intake during our evolution are most likely drastic underestimations.”
Our ancestors may have had salt licks, although as shown above, eating sodium-rich soil does not supply a lot of sodium.
While true that rainwater can contain sodium this is misleading as the sodium content of rainwater is very low. If you have ever tasted rainwater it does not taste salty.
“But alas, the mantra has always been that the strict vegetarian diet of our early ancestors only provides around 230 milligrams of sodium per day, and that even a carnivorous diet only provides around 1,400 milligrams of sodium.”
These values appear to be reasonable estimates.
“These low estimates led most experts to believe that our current salt intake is two to twenty times what our ancestors would have consumed. And if we didn’t eat that much salt during our evolution, then our current intake can’t be good for us! (Or so the mantra goes.)”
This is how theorising based on evolutionary principles is often carried out.
“No one truly knows how much salt our Paleolithic ancestors ate or how much salt our human brain evolved on— but it’s probably much more than what most experts think. Some experts believe that 45 to 60 percent of our Paleolithic ancestors’ calories came from animal foods 39 that are naturally high in salt.”
As stated above, animals foods are not “naturally high in salt”, at least compared to modern foods with added salt.
Conclusions
Salt may not be as bad for people as has often been claimed. But the poorly constructed evolutionary rationale in this book used to justify a diet high in salt is badly referenced, contains little to no actual evidence, and includes a number of factual inaccuracies. The references that are used appear to have been chosen to fit into the narrative of the book and references that did not fit the narrative have been inaccurately reported. Factual statements that were not referenced were often inaccurate.
I did not find any evidence in this chapter that supported the suggestion that humans evolved on a diet high in sodium and the poor quality of this chapter does not give a great deal of confidence in the rest of the book. If you want to enjoy reading popular books related to nutrition I recommend that you do not attempt to check their factual accuracy.
The call of the Honeyguide 
I don’t think the author knows anything about human evolution
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Blood does contain a fair amount of salt. I’ve seen videos of e.g. the Masai slaying an animal and drinking the blood. The Inuit also drank blood. A litre contains, apparently 9g of salt. Blackpudding a standard part of British and Irish diet until very recently. Made primarily from blood. The Spanish, Portuguese, Poles etc all eat it.
The recent Canadian research done on optimal salt intake, suggests very strongly that the optimal intake for longevity being in the region of 6-7g per day of salt, as against sodium, that this level of intake is what we are best adapted to consume, if not indeed more. As the measure is of salt lost in urine being a surrogate for salt consumed, this can be exceeded a lot in intake by those who sweat a lot.
In the modern diet, there is added salt such as in bacon and other preserved meat and fish. It could be that this is simply substituting for salt that otherwise would be sought by humans.
I agree that the historic stuff is speculative, but what should more concern us is what is best. What does the evidence show?
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It is certainly true that many populations have consumed quite a lot of salt during recent millennia, although this seems a comparatively recent development that is tied to agriculture. However, not everyone considered recent agricultural populations to have been the best examples of good health.
It is perhaps a more interesting question to ask why the amount of sodium we need for optimal health is rather higher than the sodium intake consumed during our evolution.
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Thanks for doing this fact check. The book seems like a mess. The only way our ancestors could have had a high-salt diet is by the same means we have a high-salt diet today: added salt. Either from liquid seawater or salt deposits. This is a very difficult hypothesis to test, but it seems unlikely that our ancestors in Africa would have had consistent access to seawater or salt deposits, at least before extensive trade. Whole foods don’t contain high levels of salt because the osmolarity is incompatible with life.
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Masai, Inuit etc., drank blood. 9g salt per litre. Blood also used in many places to make black pudding etc.
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Blood has a lower concentration of NaCl than you suggest: about 140 mmol/L Na and 100 mmol/L Cl in humans. That’s about 1.5g of Na and 1.7g of Cl, for a total of 3.2g per liter. Furthermore, neither the Inuit nor the Masai live like our distant ancestors. The Inuit are ancestors to only a small percentage of the world’s population and the Masai are herders who drink more milk than blood and are also not ancestral to much of the world’s population. I’m sure hunter-gatherers ate some blood along with their meat but you can’t eat more blood than is contained in the animals you kill. They were certainly not drinking a liter every day.
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Thanks, I don’t recall reading of any examples of recent hunter-gatherer groups specifically seeking out natural sources of sodium, at least not the way predominantly plant eating animals do, probably because they get enough from the animals in their diet.
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Very well written!
Please read the latest article from dr.Cordain along with the previous ones. It has got 121 reliable references while his detractors only have few messed up cherry picked tales like this.
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I checked what you wrote, Stephan. I think it’s more like 6g per liter.
One point. We know little about our ancestors’ behaviour. They may have had salt lakes which they went to. There’s always been a trade in salt. People were a lot more sophisticated in their behaviour than they are given credit for.
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The error that evolutionary detractors always make is that they make a strawmen to fight against.
Neither Cordain nor any other reliable ancestral health advocate merely points out a tale about human evolution. The latter theory is one piece of the puzzle that has to fit with antropological evidence (“contemporary hunter gatherers”), RCTs, epidemiological evidence, animal studies, in vitro studies,etc… is the triangulation between ALL of this stuff that makes a solid argument toward causation.
I’m really fed up with using evolutionary theory at personal use to confirm alleged theories at one side and on the other blaming who use the same theories with other hubris ov evidence.
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Hello Gearoid,
Here is my math. Human blood contains about 140 mmol/L Na and 100 mmol/L Cl. The molecular masses of Na and Cl are 11 and 17, respectively. (11 x 0.140) + (17 x 0.100) = 3.24 g of Na and Cl. If there is a mistake here I’m happy to be corrected.
I agree that we know very little about our ancestors’ behavior so we can only guess. But in my opinion our best guess come from current and historical hunter-gatherers, most of which don’t have much added salt. I acknowledge that this extrapolation isn’t ironclad and there was likely a lot of variation in access to added salt and salt water.
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I’ve a probing question for Stephan and Matthew.
There is no disputing that humans have a taste for salt which leads them to eat the amount of it, they do, averaging around 7g per day of sodium chloride. The fact that this level of consumption pans out as having the longest survival suggests that it’s the best level. Not only have they a taste for it, such that if they’re deprived of it, food tastes delicious with it, but if they overconsume it, an aversion develops and the food tastes “too salty.” This is clearly a salt managing “system.”
A lower consumption can be managed by aldosterone and other mechanisms, one of which is more absorbtion of it, with concomitant water from the colon. Constipation results from this. Overconsumption results in less absorbtion and can cause diarrhoea. It also causes the body to make water from food, to help to get rid of it. This was shown by very recent research.
The question is this. If the salt managing system goes for 7g per day, how did it go for this excessive level, by their thinking?
You don’t know how humans might have got this level in times past, but that doesn’t mean that they didn’t. Animals know where to look for it. Humans probably evolved near sources of salt, like salt lakes etc., drank blood and so on. Research shows, more and more, evidence of a fair degree of unexpected sophistication in our ancestors.
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Forget about fairy tales my friend.
Matthew easily dispelled them in his review and Cordain has got a HUBRIS of reference about the detrimental effects of high salt consumption.
You reported a distorted view about how it works.
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Hi Gearoid,
First I want to explain that I don’t have much of an opinion about the health impacts of salt. The evidence seems so conflicting to me that I haven’t taken a position on it. I’m also not an expert on the evidence. So I don’t really have a dog in the fight when it comes to modern-day salt intake recommendations.
But let me ask you a rhetorical question that I think is similar to what you are asking. Do you think there is a “sugar managing system” that optimizes our refined sugar intake? In the US we get about 14% of our calories from sugar, and nearly all affluent countries get between 10 and 20 percent. This is what we are choosing– few people like low-sugar diets, and few people like diets that are above 20% sugar. We crave sugar and we miss it when we don’t get it. I would argue that our sugar intake has not been optimized for health by a “sugar managing system”– we are drawn to refined sugar because we’re wired to like sweetness, and for that reason we consume more of it than is good for us (but our preference tops out at a certain intake level). We’re wired to like sugar, salt, glutamate, starch, and fat, and today we have easy access to all those things, and I think that’s likely the reason why we eat so much of them.
But whether our high intake of salt is harmful or not, I don’t know– I find that question difficult to answer. The observational evidence showing that the lowest mortality level correlates with a salt intake of 7g is not convincing to me. It could easily be confounded. And it seems hard to believe (but not impossible) that the optimal salt intake would be far higher than the intake of many of our ancestors.
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Matthew likes awkward questions. I’ve asked them. I’ve no interest in slogans. THere was no distortion in how I described the situation. Latest science. The PURE study level showed around 7g per day as average and such a consumption gave the longest life expectancy. Fact, and it seems pretty robust.
Well Matthew? Can it be that there’s some stuff about people long ago we don’t know? I think it’s pretty likely that there is.
It is possible to reduce your salt quite a lot as I did for many years. I don’t think it did me any good but I’ve no way of being sure. The point is that I’ve found that I can eat considerably more, up to my natural desire for the stuff without budging my blood pressure. If I deliberately overdo it, it will raise it, but at that stage it doesn’t taste good. It appears that overdoing sugar is a much bigger factor in blood pressure.
Sure, if it does raise your BP and reducing sugar or elmininating it doesn’t do the trick, try to reduce it by salt restriction, but to prescribe this for the whole population is nuts, when for 90% or more it has no effect and may be doing some harm to some of them, as the longevity curve seems to show.
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I think there are different but related questions in this. How much sodium did our distant ancestors consume, and does that tell us what we should consume now?
I would say that overall evidence does suggest that we now consume rather more sodium than our hunter-gatherer ancestors or related primates. The addition of salt to the diet appears to be an aspect of agriculture. However, we also now probably eat less salt than our recent ancestors, as salt intake has decreased in recent decades, partly due to improved food preservation and refrigeration, we just don’t use as much salt to store our food anymore.
I would be cautious saying that the low levels of sodium intake of hunter-gatherers are necessarily the best for everyone now. Just because their diets were low in salt doesn’t necessarily mean ours should be as low. The J-shaped curve emerging now for salt intake in epidemiological studies is interesting, as is the evidence for an effect on insulin resistance. Insulin resistance does not seem to have been a problem for hunter-gatherers and so low sodium intake would not have had any detrimental effect, perhaps it does now?
Most animals seem to have a drive for sodium, as it is usually a rare mineral in the wild, so when given easy access to it they tend to over-consume beyond requirements. I believe the same thing occurs in farm animals given access to salt.
High salt intakes do seem to have some negative health effects, but perhaps a moderate salt intake of around 7 grams is actually better, on average, in modern populations than the low levels consumed by hunter-gatherers. I think that is an interesting question.
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But humans don’t naturally overconsume as it starts to taste too salty. Hence the average consumption being also apparently the ideal one. A hot of the presses headline about Salt increasing heart failure done on a Finnish study is most interesting in this regard. Those in the highest quintile had more heart failure BUT this quintile was a very high level of consumption whereas the lowest was around 6.8g, i.e. at the ideal level. The authors then assume that lower than this would be better, either ignoring the PURE study or simple not knowing about it. This is not a surprise to me as I worked with such academics all my career and many if not most of them don’t actually read a fraction of what they write. They are actually too busy.
Now what would make people overconsume salt as in the Finnish Study. It may well be that some processed foods, full of salt, don’t taste salty as the other tastes overwhelm it. I also suspect that Insulin Resistance has something to do with it, as it appears to something to do with everything except the price of fish!
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That depends on what you mean by over-consume. It is very difficult to eat a lot of sodium without added salt, which is a relatively recent development. Everyone now consumes a lot more salt than our evolutionary basal requirements must have been.
Even if for example, we take 6.8 grams a day to be the ideal level, much of the world still consumes rather more than this.
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I think it’s true that insulin resistance has a greater impact overall. However, evidence shows us that whenever we steer away from the evolutionary framework, we go toward a “detrimental curve” in the sense that the more you deviate from that template, the more you go toward issues.
Health is impacted by many many variables and we can observe that an active person, who sleeps and exercise and eats a whole food nutrient dense toxin free diet, even if he adds some salt in his recipes, can stay relatively healthy.
But the devil is always in the details and the term relatively is the key factor. If epidemiological studies compare the average joe with the aforementioned “fitter” sample, there’s no way that the outcome of the study is in favour of the latter, but would he be better off without salt or other x y z variables? Who knows?
We should compare a paleo diet with and without salt that is quite difficult to do so far.
Thus, if I had to choose, I would stay on the “safer” side of the river.
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I see your point within the context of a paleo diet.
But if we consider salt restriction in modern populations it is within the context of an unhealthy diet that often leads to insulin resistance and obesity etc. While I agree that high salt intakes seem detrimental I can see a potential at least that, with the context of modern populations, reducing salt alone to the low levels seen in hunter-gatherers may not be totally beneficial.
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But, folks, the PURE study was from countries all over the world and the average was about 7g and this coincided with the longest survival. Now on a Paleo, or certainly an LCHF diet, cutting back on salt will constipate the hell out of you. Personal experience. I had a very low salt intake (added no salt at all) for about 20 years. Had given it up. Ate TONS of fruit. Never constipated. I think I had a measure of fructose-intolerance. I just had to up my salt to fix myself after starting LCHF. All the experts say you have to. My blood pressure has only risen when overconsuming experimentally.
The business of fibre is fraught. Recent RCTs show that for the chronically constipated, cutting out fibre totally gives the best result. A small percentage of these just may be salt-deprived (deliberately).
I’ve experimented on myself in this regard. As I do a lot of cycling, I have to take more salt. Not doing so will constipate. Topping up by taste will prevent. Overswilling salt (drinking salty water etc) will cause loose stools and raise my BP.
One of the “experts” said on this recent Finnish thing.. the heart doesn’t like salt. This is bullshit. Had he said that the heart doesn’t like salt if its overconsumption leads to raised bloodpressure, he would’ve been spot on. But by careless statements you lead to a nonsense position. Cut out the salt entirely. No bueno.
This has turned into a good discussion!
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I’m always open to change my mind in front of strong evidence. In this case, the most convincing source for me so far is this:
http://thepaleodiet.com/physiological-mechanisms-underlying-high-salt-diets-cancer/
Paleo diets are not necessarily low carb diets, I believe to adjust the carb intake for personal needs
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Alessio, the Japanese eat a lot of salt. Their incidence of stomach cancer is high, but their breast cancer and bowel cancer rates are much lower than ours. While it has been shown that high sodium and low potassium can cause hypertension there, in most places they don’t have particular hypertension and are very longlived. So, I remain in doubt about this issue.
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Can you give me the reference about high salt intake of the “healthy” part of Japan that you mentioned?
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Epidemiological studies are so far from causation
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This is true, although aren’t most sodium recommendations based on epidemiology to some degree?
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Reading Cordain’s articles, you have many hints aside from epidemiology. It looks very convincing to me so far.
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Gearoid,
In the PURE study:
1. Average sodium excretion was 4.9 grams per day (Figure 1A from this paper: http://www.nejm.org/doi/pdf/10.1056/nejmoa1311989)
2. All cause mortality was lowest between 4-5.99 grams of sodium excretion per day in multivariable analysis, although only significantly lower when comparing it to those eating less than 3 grams or more than 7 grams per day. (http://www.nejm.org/doi/10.1056/NEJMoa1311889#t=articleResults)
Unless you’ve seen different papers than me, 7 grams wasn’t the average or the sweet spot for longevity as you describe it in the PURE study.
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Unfortunately, the PURE study used an approach to measure sodium consumption that is known to be statistically weak and to produce erroneously J-shaped curves. PURE relied on a single spot urine sample (i.e. peeing once into a specimen container at the start of the study), then used the “Kawasaki formula” to try to extrapolate this to the sodium level that would be found in a 24-hr urine sample (i.e. peeing throughout a 24hr period into specimen containers), The problem is that this approach has been shown by other researchers to be unreliable and to produce a J-shaped curve when relating sodium to cardiovascular disease risk. When researchers use multiple 24-hr urine samples (that is, collecting several days worth of urine across the study period), they get a linear relation between sodium intake and cardiovascular disease risk. In fact, several research teams have gone through the trouble of reanalyzing their studies (which had captured multiple 24-hr urine samples) to only rely on the *first* urine sample collected (and use the Kawasaki formula), and this transformed the linear relation to a J-shaped one (sources: https://academic.oup.com/ije/article/47/6/1784/5040736 , https://www.ahajournals.org/doi/10.1161/circulationaha.117.029028 ).
Salim Yusuf, the lead PURE researcher, has said “I worry how much of our work is potentially confounded.” and “Would I like better data? Yes.” The American Heart Association has stated that “the findings in this [PURE] study are not valid and you shouldn’t use it to inform yourself about how you’re going to eat.”
Also, people with normal blood pressure (under 132 mg Hg) actually do experience a small drop in blood pressure (~1.5 mm Hg) when significantly decreasing their sodium intake (according to Graudal’s 2019 meta-analysis of 133 studies). However, the majority of the studies were of 2 weeks or less in duration, and it is known that blood pressure can continue dropping gradually for at least 4 weeks (and perhaps longer) when lowering salt intake (see https://www.ahajournals.org/doi/full/10.1161/HYPERTENSIONAHA.117.10017 ). Furthermore, according to Nancy Cook, a biostatistician at Harvard Medical School, a small drop of 2 mm Hg SBP would translate to roughly 67,000 fewer heart attacks and 34,000 fewer strokes and TIAs each year across the US population. So what appears to be a small reduction in blood pressure could actually save thousands of lives each year.
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I think there may be a few problems here…
“The only source I could find for the sodium content of aquatic plants was a paper from 1973 called “Sodium Dynamics in a Northern Ecosystem“, which examined the role of water plants in the diet of moose living on Isle Royale, Lake Superior.”
From my somewhat ancient memories of geography lessons, isn’t Lake Superior full of *fresh* water?
“African catfish contain 406 mg of sodium per kilogram of raw catfish, which is not a high level.”
According to my encyclopaedia, African catfish live in *fresh* water…
Matthew also talks about salt levels in modern-day wetlands, whereas James DiNicolantonio was talking about surviving wetlands when climate change had increased temperatures.
Doesn’t warming up a mildly salty marsh make it a rather dryer and much saltier marsh?
But of course, I actually like salt and detested the taste when I tried to restrict myself to the 2300 mg of sodium per day “official limit”. I’m obviously biased…
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Table salt seems to have a 1.55:1 chloride/sodium ratio. Is this a similar ratio as is found in wild plant and animal foods? Human milk typically supplies 3 times more chloride than sodium, i.e. per 2500 kcal mature milk about 550 mg sodium and 1500 mg chloride, while the transitional milk had twice as much, and the colostrum even more (Human Milk Biochemistry and Infant Formula Manufacturing Technology, 2014, p. 57). Why this high chloride/sodium ratio? Is it a reflection of the mothers high salt intake, and perhaps low potassium intake? Cow milk seems to have a 2:1 ratio on average. Maybe it´s the chloride we need more than the sodium – in which case potassium chloride could be a better option than sodium chloride.
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Of course, humans didn’t spread around the world without encountering the sea, migrating along coastlines, hunting sea animals, crossing the sea if necessary. That’s probably the point at which our tolerance for salt was tested by natural selection, and any advantage of a higher intake went into the genome.
The world’s longest-living peoples almost all live on islands, and island people living traditional lives have or had very low rates of chronic degenerative diseases. Obviously, natural exposure to the opportunity to eat very salty foods does not shorten life or impair health. This is not the same thing as adding salt and other sources of sodium (often without chloride) to processed food.
But that was never going to turn out well even without the sodium.
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Sorry, do you have any data to support your hypothesis about salt intake in islanders?
Eating seafood and living near the sea doesn’t mean eating high salt…you have to have data to support it otherwise is purely speculation and fantasy. We have to separate facts from fiction.
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Evidence that the sea is salty:
there is 3.5g salt in 100ml sea water. Sea water is available in coastal regions and tastes good if you haven’t eaten salt recently. Salt itself dries on rocks near the sea and can often be found crystalised.
Evidence that littoral foods are salty
When James Cook arrived in New Zealand he was shown 3 antiscorbutic plant species by Maori.
One of these, Tetragonia tetragonioides, is native to Argentina, Australia, Chile, Japan, and New Zealand. It is a halophyte, only growing in salty soil, and still contains 107 mg sodium per 100g when cooked, boiled, and drained, without salt. Edible kelp supplies 233 mg Na per 100g. Mussels, probably the most reliable food source on a temperate rocky coastline, supply 369 mg Na per 100g.
Evidence of littoral migration
If we observe the current pattern of migration from Africa and the Middle East to Europe, most of it takes place along and across bodies of water. And that is without migrants relying, as they would have in the distant past, on the sea as a source of food even in the most barren regions.
Of course I cannot prove that anyone took advantage of these salty foods or the salt in seawater in prehistoric times. For all I know, they were religiously avoided until some heretic introduced salt as a thing.
The point I make is that the ancestors of most, possibly all (unless it’s believed the peoples of central Africa have always stayed put, I’m not up with this), modern humans had access to salt and the opportunity to be exposed to relatively high intakes while also exposed to relatively strong selection pressures (the combination of littoral migration and existence, as well as ocean travel, during migrations imposed by other stresses). After that, humans as they moved inland again developed trade to supply themselves with salt, and found inland salt sources such as those of the Himalayas and exploited them.
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Do you manage to drink sea water?
I find hard to reach high salt daily intake with fish, seafood and other fresh stuff..
Nevertheless, I can’t exclude it…
My perspective is not focusing on scant evidence alone, but to put together many pieces of a big puzzle.
And doing that, I still think that high salt diets are not a so good idea.
Of course I’m prone to change my mind in front of a more solid evidence.
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I often drink small amounts of sea water when I’m swimming, have used it when cooking near a beach. I’ve seen my dog drink it too. But at 3.5g/100ml that is still not really getting a lot of salt.
We have to define what high salt diet means – I think by 7g of sodium, at least in one dose, there are definitely more adverse effects in sensitive than benefits in non-sensitive. In the epi studies 3-4g seems ideal, but that’s higher than the <2g recommended. But you're not going to get very low without replacing sodium with potassium.
My point is really that if there is an important advantage of sodium restriction we will see it in populations with no access to salt, compared with populations who have easy access because they are near the sea. Nothing in human history tells me that living near the sea has been a handicap or a constraint on longevity.
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It doesn’t really matter to me weather our ancestors consumed little or lots of salt because I have done an experiment on my own to test the affects of little and moderately high amounts of salt on my body, and this is what I found. After being on 3 high blood pressure medicines and a low salt diet prescribed by my doctor for a couple years, I read this book. This is when I chose to do the experiment. I decided to consume as much salt as I wanted and added far more fruits and vegetables to my diet. Adding the extra salt made eating these vegetables far more delicious so it wasn’t hard to eat plenty every day. At the same time I quit sugar… completely. No pasta, no bread and definitely no refined sugar. The results were staggering. Within 4 days, yes 4 days, my blood pressure dropped enough to quit taking 2 of my high blood pressure meds. After a week I no longer needed any of them. So I don’t know about our ancestors but for me, SUGAR was the problem, not salt. I’m so happy I found this book. To me it was a life saver. I can’t thank James DiNicolantonio enough for writing it!!
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This is what we know for a fact, if there was a source of salt somewhere and they were humans or any other animal and tried it- they would have ate the shit out of the salt because salt is a flavor enhancer. End story.
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Sodium is critical for brain health and development, the only problem I see in this theory is locating human development inland and not at the marshes at the river mouth, where salt is plentiful.
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