Salt, in the form of sodium chloride (NaCl), is added to almost everything these days. This is something you’ll quickly recognize if you survey a regular grocery shop, looking over the labels of the products it offers. You’ll see that salt is found in everything from bread to sausages to pizza toppings to ketchup to tortillas. Basically, the majority of food products that come in a box or wrapper have salt in them. The salt serves several purposes: it helps preserve the food, appeals to salt-conditioned consumers, and binds water, thereby potentiating increased bulk. Additionally, it makes us thirsty, which helps explain why places that serve drinks (e.g. bars) tend to offer something salty to their customers, like salted peanuts for example.
How is all of this salt affecting us?
The salt issue
Conventional nutritional teachings imply that salt is something we’d be wise to take in less of. Not everyone is on-board with this idea though. Over the past couple of years, what I consider to be an unnerving trend has been sweeping across parts of the nutritional landscape, including throughout certain ancestral health-oriented territories. Some influential bloggers, book authors, and researchers have made the case that the longstanding public health recommendation to limit the consumption of salt is unwarranted and should be revoked – or at the very least modified. A subset have even gone as far as to say that many of us would benefit from taking in more sodium chloride, as opposed to less, which goes completely against what we’ve long told to be true about this white powder. This rebellious offensive against the status quo is understandable alluring, having attracted the attention and approval of many a health-conscious dieter; however, a wealth of evidence strongly suggests that it’s misguided.
So as to try to counteract this trend, I’ve devoted a lot of attention to the dangers of dietary salt here on the site, focusing particularly on the effect it has on the cardiovascular and immune systems. I haven’t touched on all the issues though. Nor have I summarized the key ones. That’s something I thought I’d do now…
A summary of ‘old’ and emerging issues with a high salt intake
Dietary salt has long been recognized to have blood-pressure raising effects. Some dispute that there’s a relation; however, these people are very much in the minority. As I see it, they’re also seriously misaligned with the evidence. If you’re interested in surveying the support for this view yourself, I’d recommend starting with the following articles: 1, 2, 3. In particular the first one is great, and deserves more attention, as I see it. Also, you may want to check out some meta-analyses on the matter (e.g., 4, 5).
- Cardiovascular disease
Hypertension is a well-recognized risk factor for cardiovascular disease; hence, one would expect that a high salt intake is also a relevant risk factor. Seeing as cardiovascular disease doesn’t happen over night, but rather is something that develops over a long period of time, as a result of a combination of factors; one wouldn’t expect it to be easy to assess the impact of dietary salt, as an isolated variable, on cardiovascular disease outcomes. This is reflected in the literature, which features some apparently ‘conflicting findings’. However, after accounting for methodological limitations, what emerges is a pretty clear picture (6, 7, 8, 9).
- Metabolic acidosis
Dietary acid-base load has emerged as an important, underappreciated factor in health and disease. One of the major issues in this respect is that we’re currently taking in excessive amounts of acid-generating foodstuffs (on a societal level), at the expense of base-yielding one. NaCl factors into this equation in a major way, in that it’s a potent acidifier (10, 11).
- Gut dysbiosis
Fairly recently, increased scientific attention has been devoted to the effects of dietary salt on the gut microbiome (12, 13, 14, 15, 16). The picture that’s emerging is not a pretty one, in the sense that a high salt intake appears to seriously mess with the gut. This, in turn, will seriously mess with the body as a whole. To be fair, most of the research to date has been conducted in animal models, with pretty high doses. However, a 2017 pilot study in humans found that even a moderate high salt challenge, involving an increased intake of 6 g/d, reduced intestinal survival of Lactobacillus spp., caused increased generation of pro-inflammatory TH17 cells, and raised blood pressure (12). Furthermore, it’s important to note that the idea that salt has a potent effect on the gut microbiota has a clear biological basis to it.
- Inflammation and autoimmunity
Recently, it’s also become increasingly clear that dietary salt has a potent impact on the body’s immunological milieu. This obviously relates to its effects on the gut microbiome. The consequences of over-salting come across as alarming (12, 17, 18, 19, 20, 21). As I see it, there’s no question that the high intake of NaCl in the modern world is a significant underlying cause of the current pandemic of inflammation-related diseases of civilization.
- Kidney disease
The kidneys are of particular importance in the discussion about salt, in that sodium plays a critical role in the regulation of kidney function and health. High sodium, particularly when combined with low potassium, is detrimental to renal physiology and durability (22, 23). Intake reductions can help prevent and ameliorate kidney disease (24, 25).
- Cognitive impairment
Emerging data from animal models support the notion that a high salt intake adversely affects cognitive function (26, 27, 28, 29, 30, 31, 32). More research, involving human subjects exposed to doses encountered under settings of contemporary living, would be required to fully substantiate the perceived link.
A high salt intake has been associated with increased cancer risk, most notably susceptibility to gastric cancer (33, 34, 35).
Note: This list is not exhaustive. It does however feature some of the key issues. A noteworthy observation is that issues such as hypertension, cardiovascular disease, and autoimmunity are common in westernized, high-salt areas, whereas they are virtually absent among traditional low-salt populations, such as the Australian aboriginal hunter-gatherers, the African Bushmen, and the Amazonian Yanomami.
In fear of repeating myself, I’ll now talk a bit about the evolution of NaCl consumption in humans. The reason I’m devoting so much space to this matter is that I consider it to be the crux of the salt issue.
As mentioned earlier, even within certain sections of the ancestral health community, the notion that salt really isn’t something we need to be particularly concerned about has taken hold. I find this somewhat absurd, considering that it’s well established that the ancestral nutritional conditions and inputs to which the human genome was adapted by natural selection over millions of years of evolution were low in sodium (1, 36, 37, 38). Our primal forebears obviously didn’t leave detailed dietary records behind; however, great insights can be gleaned from ‘reconstructing’ our ancestral nutritional environment, assessing the exposure to salt among terrestrial life forms in general, and reviewing the salt intake of contemporary and historically studied hunter-gatherer groups.
Actually, one might argue that it’s not even necessary to look at the scientific evidence to recognize that the notion that we’re wired for a high salt intake doesn’t hold up from a Darwinian point of view. All one has to do is acknowledge that our naturally living ancestors didn’t mine salt and only ate natural foods, most of which harbored little to no sodium. They didn’t add salt to their meals or eat potato chips, bacon, or any of the other processed, salty foods we have available to us; hence, their NaCl intake would by default have been many times lower than the ~10 grams we on average take in each day in western societies – a dose that we’re most certainly not physiologically prepared to safely handle, particularly seeing as we’re taking in relatively little potassium – a mineral abundantly present in fruit and vegetables that helps offset the blood-pressure raising effects of sodium.
The following quote, derived from the excellent and concise paper entitled “Salt and hypertension: why is there still a debate?” perfectly summarizes these evolutionary recognitions:
Millions of years of the successful existence of ours and related species in a salt-free environment is sufficient proof that a low-salt diet is man’s original and natural diet, is compatible with normal physiology, and is safe. The modern man while well adapted to low-salt diet is poorly equipped to cope with the salt surfeit imposed on him in recent times. (1)
I’ve heard it suggested that people who are fairly physically active have substantially elevated sodium requirements; a notion that strikes me as debatable/questionable, particularly seeing as we evolved as physically active hunter-gatherers under sunny, low-salt conditions, something that would indicate that we’re well-adapted to perform well, physically, without the addition of a lot of sodium. If you sweat a lot, you may certainly require more sodium, but not that much more.
Given that we’re evolutionarily accustomed to a low NaCl intake, it’s not really surprising that a wealth of scientific studies suggest that the recent emergence and widespread consumption of high-salt diets have thrown our physiological systems out of balance, giving rise to malfunction and disease. In general, one would expect that the ideal would be to approximate the evolutionary norm/hunter-gatherer standard with respects to electrolyte consumption, seeing as that may be said to represent the input of physiological adaptation.
How can we avoid the issues associated with a high salt intake?
The most obvious answer to the question above is that we can cut salt from our diets. By taking out pernicious, NaCl-heavy food items (e.g., potato chips, salted bacon) from one’s diet, replacing them with natural, unsalted foods, and not adding salt to one’s meals, significant strides towards a more evolutionarily prudent NaCl intake can be made. Realistically though, many will find it difficult/impractical to get all the way down to where our naturally living ancestors were at, at least on some days, such as when they’re eating out or act on cravings for sugary, processed food, seeing as salt is added to almost everything these days.
This brings up the question of whether there’s anything that can be done to alleviate the damaging effects of a high salt intake. One important measure is to eat a lot of potassium-containing fruits and vegetables, as potassium is important with respects to counterbalancing the effects of sodium. Personally, I also tend to consume some traditionally fermented vegetables on such occasions, with the aim of counteracting adverse impacts on the microbiota. These measures don’t fully offset the harmful effects of excess salt; however, they do take the edge off certain issues.
In light of the massive body of research linking a high salt intake with everything from hypertension to inflammation to cognitive decline, I find it quite concerning that we’ve seen a trend towards increased saltiness in some areas, not just among junk food eaters, but also within certain diet and health-conscious circles. This is not some abstract, obscure issue, but rather something that’s directly affecting people here and now. I know of individuals who eat a lot of salty foods and regularly add salt to their meals – not because they’re careless, but rather because they think it’s completely safe (healthy even) to do so.
Much of the reason why salt is low on many people’s list of dietary concerns is probably that it’s perceived as something natural and that it only constitutes a very small percentage of our diets in terms of weight. What’s important to recognize though is that it’s our evolved biology that sets the constraints for what we’re able to safely tolerate and process, meaning that any input, ‘natural’ or not, that falls outside the boundaries of what we’re adapted for is liable to be problematic.
It all begs the question: Why would anyone promote or support the idea that salt isn’t something we need to be concerned about?