Let’s play a game.
What substance commonly found in a suburban home ticks the following boxes:
- Has influenced human health, medicine, politics, taxation, commerce, food preservation, and warfare throughout the ages;
- Shows up in religion, literature, and art;
- Is a white crystalline substance;
- Has historically been recognised as a symbol for friendship, hospitality, alliance, and fidelity; and
- Is referenced in The Bible no less than 40 times.
If you would have said sugar, then you would have been wrong. Although, I’d understand the logic behind your answer.
If you would have said cocaine, then you would have also been wrong. But, it’d be quite funny and interesting if that’d been correct. You do probably find it in plenty of suburban homes, but that’s a matter for another article…
The substance we are talking about is salt.
Salt has played a significant role in human evolution, civilisation, and culture. It has been used throughout history to preserve food, pay soldiers, heal wounds, baptize babies, and pay for things. Without salt, our food would be tasteless, bland, boring. We’d also be walking around like zombies with many of the symptoms that come with having low levels of sodium in your blood (also known as hyponatremia). Sounds terrible!
Given the role that salt has played in our history, why does it seem to be ‘common knowledge’ that salt is bad for you? Is it really true that salt intake is associated with increased risk of high blood pressure, heart disease, stroke, and stomach cancer?
So often we see modern health and nutrition advice at odds with tradition and ancestral behaviours (aka ‘what your grandma would tell you to do’). My grandma taught me to salt my food liberally. .Why? Because it tastes good,makes you feel better, and is what her own grandma would have taught her to do. So who do we trust - grandma or the science?
Sometimes, common knowledge can be misleading, especially when the truth is more nuanced. This is especially the case with our modern understanding of optimal human nutrition. There’s too much dogma (“salt is bad for you”) and not enough nuance (“well, it depends…”).
There’s a certain wisdom in traditional behaviours. I mean, think about it, why else would a traditional practice or habit have been established? And why has it survived for so long?
Usually, it’s because there’s an inner truth or effectiveness to the tradition. This is one of the central ideas of the phenomenon known as the Lindy Effect. It’s also a central idea in evolutionary biology (i.e. fitness and natural selection, which can apply to the transmission of cultural ideas as well as genetic adaptations).
So - in this article, we will explore the influence of salt on human evolution. We will look at the subject through an ancestral lens to try and tease out the nuanced truths relating to salt and its role in human nutrition. Lastly, we’ll compare this with what the science has to say, and give you a framework you can use to make informed decisions for yourself around how much salt to consume.
Without further ado, let’s dive in!
Why Should We Care About Our Evolution?
1. Healthspan vs. Lifespan
It’s tempting to think that modern science has figured everything out, and that the lessons of nature and history need not apply to subjects like health and nutrition. After all, we’re living longer than ever before, curing previously incurable diseases using novel therapies and techniques, and learning more about our physiology every year, right?
The truth is that while lifespan (how long we live) has increased by three decades since the mid 20th century, healthspan (number of disease-free years we live) has not.
Figure 1: Image credit (Longevity leap: mind the healthspan gap - PMC (nih.gov)). A: The world population continues to grow towards nearly 8bn people, with the cohort of people >70 growing much faster than those <70. B: Population age distributions are becoming much more weighted towards old people.
In fact, current data suggests that one-fifth of our lives will be spent living with symptoms of disease. One fifth!
2. Modern Diseases
Historically, communicable diseases were the ones that affected our health the most - think HIV, hepatitis, malaria, poliomyelitis, tuberculosis, influenza, and more recently COVID-19. Understandbly, these diseases have been at the center of global health concerns and initiatives as they are transmittable between people, across borders, and threaten the lives of millions. Though this is true, today, we also suffer from an “invisible epidemic” of non-communicable diseases (NCDs), which represent the leading cause of death and disability worldwide.
Cardiovascular diseases, cancer, chronic respiratory diseases (including chronic obstructive pulmonary disease and bronchial asthma), and diabetes-related metabolic disorders account for 80% of all chronic disease related deaths. This level of sickness and frailty imposes a huge economic burden and it is placing pressure on many public health systems around the world.
The tragedy is that most NCD related disease and deaths can be avoided by limiting basic behavioural risk factors. The main ones being smoking, poor diet, excessive alcohol consumption, and insufficient exercise.
And so, while we are living longer, we are not necessarily living healthier in those extra years. Many of these diseases are classed as ‘modern’ afflictions, given that they either weren’t around 50-100 years ago, or were far less frequent. Clearly, then, something seems off.
3. Maybe History Has Something to Teach Us?
While concerning, this is nothing new; these issues have been developing for decades. And, if you follow any leading names in the now enormous health and nutrition space, then you will be familiar with these trends.
We bring this up to stress that, sometimes, things are too complicated for scientific research and consensus to give us a clean, organised answer.
A seemingly simple question like “what is the best diet for humans to live optimally” leads to endless rabbit-holes and controversy. Read a bunch of different nutrition focused reddit forums (like r/vegan, r/carnivore, and r/paleo) and you’ll see passionate disagreement on even the most basic concepts. You can also find research to support nearly any perspective, and can only find the truth by doing the deeper work of analyzing the evidence yourself.
Sometimes, tradition can provide the clarity we need. Instead of doing a bunch of analysis, reading scientific papers, and trying to figure everything out, why don’t we just look at what people have been doing for many (if not hundreds) of years?
Given that historically, in some ways, we were metabolically and generally healthier (i.e. the NCDs mentioned above were not prevalent causes of death and disease), it may benefit us to study health through this evolutionary or ancestral lens. After all, we’ve seen some profound changes to our environment and habits in recent history with the introduction of agriculture, the industrial revolution, and processed food. Over that same time period, our genetic makeup and physiology hasn’t changed anywhere near as much.
We’re not arguing that you should go out foraging for your dinner, but that we should acknowledge that we are now divorced from our traditional environment, microbiome, and circadian rhythm, and that this may have negative consequences for our health.
Coming back to salt:
This article would be very long if we looked at all of the inputs into optimal health, so let’s return to our core subject: salt.
Here is a quote from Mark Kurlansky (a writer and historian) from his book A World History of Salt:
“Salt is so common, so easy to obtain, and so inexpensive that we have forgotten that from the beginning of civilization until about 100 years ago, salt was one of the most sought-after commodities in human history.”
So, how and why did salt play such an important role in our history?
The Historical Role of Salt
Salt is at the centre of the story of the development of human civilisation. Throughout history, salt has been considered a precious commodity due to its scarcity. Empires were built and destroyed on the product of salt.
Salt was so important that it influenced where and how cities were built. The oldest town in Europe, Solnitsata, hosts the remains of the oldest salt production center in Europe (5500‑4200 BC). It is located in Bulgaria and is believed to have supplied salt throughout the Balkan region.
During the early years of the ancient Roman civilisation, the first roads were built to transport salt easily to Rome. Via Salaria, a famous 240km road from Porta Salaria in Rome to Porto d’Ascoli on the Adriatic coast, was one of many ancient salt roads in Europe. Salt was very high in demand and the salt trade was highly lucrative. The Roman soldiers guarding the salt, as well as the workers and the toll collectors on the roads, were paid in salt.
The ancient roads of Rome. Image credit: Did all roads lead to Rome? | Live Science
Historically, the main reason for the addition of salt to food was for preservation. Salt preservation of meat is believed to have begun around the year 2000 BC. Salting food dramatically decreased the likelihood of the growth of harmful pathogens and organisms that spoil food. Without salt, humans would have been dependent on the seasonal availability of food, which would have hindered our ability to travel long distances and survive brutal winters.
1. Culture and Trade
Although it was originally important for its ability to preserve food, salt assumed a symbolic significance that was far greater than its functional utility or economic value.
Salt features in medicine, politics, commerce, and religious practices of many different societies. In western societies the salt cellar was traditionally a symbol of friendship and hospitality. Japanese sumo wrestlers sprinkle salt on the ground to sanctify it before a contest.
As Kurlansky explains, salt had religious significance. It served as a symbol of the covenant between God and the ancient Hebrews in Judaism and Christianity. It also shows up in key stories, sacrifices and offerings of the ancient Egyptians, Greeks, Romans, and Muslims.
As civilization and agriculture spread, salt became one of the first international commodities. Salt trade routes traversed the globe, between Africa, Asia, the Middle East, and Europe. One of the most traveled led from Morocco and south across the Sahara to Timbuktu. Salt was interchangeable for gold by Moorish merchants as early as the 6th century. In Abyssinia, slabs of rock salt, called ‘amôlés, became the generally accepted medium of exchange. Cakes of salt were also used as money in other areas of central Africa.
Salt amôlés. Image credit
2. Language
Salt has also made its way into our language.
The word ‘salary’ has its roots in ancient Rome and the history of salt. Given the usefulness of salt as an antiseptic, the Roman word for salt (sal) was in reference to Salus, the goddess of health. Part of the pay that soldiers received consisted of salt, and came to be known as salarium argentum, from which we derive the word ‘salary’.
This salary could be cut if a soldier was not “worth his salt”, a phrase that stems from the fact that Greek and Romans would buy slaves with salt.
3. Salt in the Diet
Today, 90% of the sodium in a typical US diet comes from manufactured salt that is added to food. Most of this (~75%) comes from salt added by manufacturers to processed food, with 15% from discretionary use (i.e. added salt to cooking) and the remaining 10% of our sodium occurs naturally in foods we consume.
Let’s compare this level of salt use to our evolutionary history.
In the Paleolithic era (the old stone age which began 2.6 million years ago and ended 10-12 thousand years ago), there is little evidence to suggest that people engaged in salt extraction or sought out inland salt deposits. Although some hunter-gatherers living in coastal areas may have dipped food in seawater or used dried seawater salt, it seems unlikely that salt was added to food on a daily basis in any meaningful quantity.
Preagricultural humans are estimated to have consumed only 768 mg of sodium each day from added salt (which is much lower than what we’d consume today).
The research suggests that the systematic mining, manufacture, and transportation of salt have their origin in the Neolithic Period (12-2 thousand years ago) which coincided with the development of farming, agriculture, and the use of polished stone tools. As the diet shifted towards grains and vegetables, the sodium content of the food being consumed would have decreased materially.
This contrasts to a carnivore based diet of meat and seafood in which a human can meet their sodium requirements (provided they don’t sweat excessively). As an example, the blood of livestock forms a core part of the diet of the Maasai (a pastoralist tribe living in Kenya and Northern Tanzania). Kurlansky has suggested that those tribes that hunted most of their food would not harvest or trade salt, and the dietary need for salt increased commensurate with the extent to which the diet became based in agricultural products.
Image credit: Milk, meat and blood: how diet drives natural selection in the Maasai | WIRED
Salt in the Diet of Hunter-gatherers Today
Anthropological research shows that contemporary hunter-gatherer tribes consume, on average, less than ~2.5g of salt per day, which is much less than a standard western diet. Some tribes are heralded for their cardiovascular health and lack of non-communicable diseases, such as the Tsimane, an indigenous tribe in the Amazon region of Bolivia. They consume little sodium because they eat no processed food.
In contrast, most Western societies have high levels of hypertension, cardiovascular disease, diabetes, and associated conditions. The idea today is that the high sodium levels of a Western diet raise blood pressure and increase the risk for cardiovascular disease, osteoporosis, and other diseases.
Nevertheless, this simplistic analysis ignores a whole range of other factors which might explain the lower cardiovascular and non-communicable disease risk in indigenous populations vs. Western societies, beyond salt consumption. Things like time spent outside in nature, exposure to harmful chemicals and environmental toxins, exercise, gut microbiome diversity, and social connectedness matter in determining chronic levels of inflammation, which is a key contributor to disease. Unfortunately, many epidemiological nutrition studies draw correlations between factors and health outcomes at a population level and fail to account for these types of variables.
As always, the truth about the optimal sodium intake is much more nuanced. It seems inaccurate to suggest that, just because preagricultural humans added little salt to their food, that it would be evolutionarily consistent for us to also adopt a low salt diet. The sodium content within our food matters a great deal.
The other factors that complicate the comparison are 1) fluid intake and 2) levels of sweating and activity. We’ll get back to those in a moment.
But first, we have to return to a core idea: that sodium is a vital nutrient and without sufficient amounts of it, we would not be able to function optimally.
Is Sodium Actually Bad For You?
1. Brief Introduction to the Research
Sodium isn’t an optional mineral. You need it to function properly, and if you don’t have enough of it, your body will do all sorts of things to conserve the precious sodium and other minerals that you do have. It does this by upregulating certain hormones that make you pee out less sodium in your urine. Consuming too much salt will do the opposite. It turns out that the ability of our bodies to regulate blood sodium concentrations is quite advanced…
Sodium’s main functions are to regulate extracellular fluid volume, conduct nerve impulses, maintain blood pressure, and help transport nutrients in your gut.
Sodium deficiency (known has hyponatremia) presents with a bunch of symptoms that basically make you feel like crawling into the fetal position. Symptoms include fatigue, headaches and migraines, brain fog, and impaired sympathetic cardiovascular adjustments to stress.
Take a look at this quote from research on sodium intake in mammals:
“In most mammals studied, experience with a depletion of body sodium leads not only to rapid physiological (i.e., autonomic and endocrine) adjustments for defending homeostasis but also to profound behavioral changes. The most frequently studied behavioral changes are associated with increased intake of sodium that follows loss of this cation.”
Basically, animals that are deprived of sodium will do just about anything to get their hands on it. Our psychobiology will adjust to make previously unappealing salty substances more pleasurable and rewarding.
In cases where sodium is depleted experientially, animals will often “overshoot” and ingest much more sodium than is necessary to restore homeostasis. This is because being in a low sodium state puts them out of homeostatic balance, which makes them (and us) feel horrible. The research suggests that unresolved sodium appetite can induce behavioral characteristics that are “qualitatively similar to psychological depression as well as induce plasticity in brain regions implicated in motivation, reward, and drug sensitization and withdrawal”.
Our biological adaptations to sodium make it clear that this mineral is important for optimal health. Unlike sugar, sodium is an essential nutrient.
The brief summary of our position is as follows:
- Sodium is one of many factors that correlate with hypertension at a population level, but it is not the cause. The researchers of the INTERSALT Study readily admit that there are plenty of other factors (like potassium and magnesium intake, physical activity, stress levels, and alcohol consumption).
- Rather, insulin resistance and metabolic syndrome are the underlying etiology of metabolic diseases like diabetes and cardiovascular disease.
- Low sodium diets are not all that effective at lowering blood pressure. They can also produce a whole range of negative symptoms like osteoporosis, heightened stress, and hyponatremia.
- High blood pressure is a symptom of metabolic syndrome. Doing things that improve your metabolic health (like exercise, fasting, low-carb diets, and increased magnesium intake) will fix your blood pressure.
- Your optimal amount of salt intake heavily depends on your lifestyle.
Research such as the JAMA Study from 2011 suggest that optimal salt intake is around 4-6g per day, which is much higher than recommendations from medical institutions.
Given that most of the sodium people get on a Western diet comes from processed food, and that there are plenty of other unhealthy behaviours that people who eat processed food would engage in (like drinking alcohol, not exercising, and smoking), it’s easy to see why high levels of sodium intake can be confounded by other factors in the research.
The last point we mentioned above, that your optimal intake depends on your lifestyle, is an important one.
2. Optimal Intake Based on Lifestyle
While it’s sometimes useful to look to our ancestors or traditions for clues about optimal health habits, what can’t be ignored is that our modern lifestyles differ from our ancestors, and outdated or disprove many traditions. Nonetheless, there are some long standing pillars of optimal health that are worth sprinkling into our modern lifestyles.
The first is fluid intake.
Humans have incredible evolutionary adaptations when it comes to 1) our ability to sweat, and 2) our ability to conserve water.
We are the only mammal that has the ability to sweat to control our temperature. Most other mammals pant or have fur that impairs the cooling effect when water on the skin evaporates. Our closest primate relatives — chimpanzees and gorillas — dump excess body heat by panting. This gave us a marked ability to operate in hot environments and endure high internal body temperatures when hunting. Basically, we’d chase other animals around the savannah, and they’d collapse from heat exhaustion much before we did.
The other feat of human evolution is our water sparing capacity. We evolved to consume roughly half the amount of water as our closest primate relatives, despite sweating a lot more.
The science behind this physiology is very interesting, so we’ll go into further detail in another article.
The problem lies in modern recommendations for optimal fluid intake, which can be as high as 4L per day. Basically, if you drink all that water (and we’re constantly encouraged to do so), you’re going to flush out the electrolytes in your system. All else being equal, this will mean you’ll need to increase your salt intake.
The key point is that our ancestors did not run around with their Stanley water bottles constantly hydrating. They likely drank a lot less fresh water than we do today, and so had lower sodium needs. Many of them probably got most of their hydration needs from non-water based sources - such as milk, fruit juice, and even animal blood.
So that’s key point #1. Stop overconsuming water, and drink only to thirst. That especially applies to all those endurance athletes out there. Tim Noakes wrote an instructive book on this subject called Waterlogged.
The second point is activity level.
Yes, our ancestors engaged in prolonged endurance-based hunting, and being a hunter-gatherer inherently involves a high level of activity. The point is that they were not engaging in these high levels of activity everyday.
Contrast that with people today who experience heightened fluid loss like firefighters, sauna users, NHL players, endurance athletes, and squash players (like myself). If you’re regularly sweating a lot, you need to replace the electrolytes you’ve lost if you expect to engage in this activity regularly and function optimally.
I know this first hand. After a 2 hour squash training session, if I don’t get those salts back in, I’ll be like a zombie for the rest of the day.
Bring It Together: A Framework For Salt
So, we can’t just replicate what our ancestors did, and blindly following health recommendations will also likely lead us astray. You have to adapt your salt needs based on your lifestyle.
What we often see is that, especially in people who don’t consume processed food and who are active, fluid intake is way too high and electrolyte consumption is too low. People are left frustrated as to why they feel awful (with symptoms from low sodium such as headaches, fatigue, and brain fog), despite trying to follow health advice.
The good thing is that our bodies have amazing mechanisms to signal and regulate our salt and fluid needs. As it turns out, thirst is a pretty good indicator that you need to drink more, and those cravings for salty food might also be worth listening to.
So we encourage to:
- Drink only if you are thirsty;
- Have plenty (as much as 4-6g per day) of sodium from food, added salt or supplements, especially if you are active and sweat a lot; and
- Pay attention to how you feel and adjust your intake accordingly.
We created Drivn Nutrition to address this problem (both with our products and our content), so we’re confident in the formulation and ingredient quality of our hydration mix. You can even make a similar version at home (and we’re happy to share the key inputs of our recipe). Pickle juice is another great source of salty goodness.
By making these simple adjustments to your fluid intake and electrolyte consumption, you’ll be rewarded with fewer headaches, more energy, and a sharper mind. It’s worked amazingly well for us, and we hope it does for you too!