Salt

Salt is the most common food seasoning and food preservative used in the world. Studies and different recommendations from authorities about salt have caused people to wonder whether salt is actually healthy or not, resulting in very diverging opinions. Salt is not just simply sodium, but a mineral composed primarily of sodium and chloride. The average amount of sodium in salt is 40%.

Excessive salt intake has been linked to the worsening of multiple organs and diseases. [1] But sodium is also absolutely necessary for your body to function. This section will talk about whether salt is healthy or not, and in which amounts.

High blood pressure, arterial stiffness, stroke, cardiac arrest and kidney disease

It's scientific consensus that excessive amounts of sodium lead to high blood pressure. [2] This is thought to happen because salt would provoke water retention, therefore leading to a situation of higher blood flow volume, putting more stress on blood vessels. [3]

This is considerably important for people suffering from high blood pressure/hypertension. The current recommended intake of sodium is below 2.3g daily for young people, and around 1.5g for people of African origins, people older than 51, and people with hypertension, diabetes and kidney disease [4] --however, the population averages around 3.4g of sodium daily. Considering that sodium makes roughly 40% of salt, you'd have to eat 5g of salt to take 2g of sodium, which would be around a teaspoon of salt.

Most of the sodium in the average person's diet comes from processed foods, which are made very salty to appeal to the palate as much as possible. That said, the palate can easily adjust to lower than excessive levels of salt, so by eliminating processed salted foods and replacing them with cooked-at-home foods, it'd be pretty easy to adjust the palate to be just as pleased with a safer amount of sodium intake.

High blood pressure and hypertension have a domino effect in the well-being of your body. Long-term high blood pressure leads to eventual damage to the heart and blood vessels, increasing the risk for kidney damage, heart attack and stroke. [5] [6] Excessive amounts of salt have also been shown to increase arterial stiffness. [7] Both the kidneys--because of the dense network of blood vessels in them--and the areas more vulnerable for strokes are very sensitive to high blood pressure.

With this information in mind, it'd then be important to understand what an 'excessive' amount of salt actually is.

For cardiovascular health, intakes of sodium higher than 5g daily were found to be worse for people with hypertension in this study. [8]

However, when looking at major studies that have been conducted recently, there's evidence that an average sodium intake (3-5g/d) would be more protective against cardiovascular disease than a low sodium intake (<3g/d), suggesting that the upper safe limit of 2.3g set in 2004 should be revised. [9] In this study, 17'000 people were put to the test, and a sodium intake of <3g/d was found to significantly increase the risk for cardiovascular disease. [10]

On the contrary of what recommendations say, recent studies and analyses have shown the threshold of what's considered excessive amounts of salt to be considerably higher. In this study of 133'000 people [11] [12], a higher dose than 7g/d of sodium in people with hypertension was found to increase the risk of cardiac events 1.23 times more than consuming 4-5g/d of sodium, but for people without hypertension, there was found no risk consuming 7g/d compared to 4-5g/d.

On top of that, when people with hypertension were taking <3g/d of sodium compared to 4-5g/d, the risk for cardiac events actually increased with a factor of 1.34 times higher. That means that there would be a higher risk for people with hypertension to consume not enough salt (less than 3 grams daily, 1.34 times more risk), than the risk they'd have consuming too much salt (more than 7 grams daily, 1.26 times more risk). These results held true even when researchers excluded people with known previous cardiovascular disease.

The study also found that people without hypertension consuming <3 g/d had higher risk, with a factor of 1.26 times higher. Considering the amount of people involved in the analysis, this is solid evidence that the amount of recommended salt intake would actually be too low.

The field is definitely polarized when it comes to optimal amounts of salt, and more clinical trials need to be conducted. However, current evidence suggests that:

• decreasing amounts of salt intake in people without high blood pressure doesn't make much of a difference
• a sodium intake amount of 4-5g would be best (roughly 2 teaspoons of salt)
• 7g/d (roughly 3 teaspoons of salt) would be a safe limit for people without hypertension, and probably a little lower than 7g/d should be the limit for people with hypertension

It's also important to note that <3g/d of sodium (roughly 1 teaspoons of salt) would be too little for either group.

Osteoporosis

Excessive amounts of salt have been thought to cause osteoporosis. [13]

This study found that post menopausal women consuming more than 2g of sodium daily had a higher risk of osteoporosis with high sodium intake. [14] This is not exactly clear though, suggesting a 'potential' risk.

In fact, the salt correlation with bone density loss is actually not clear at all, and no association between salt intake and bone density loss/fractures has been determined. This study looks at around 70'000 post menopausal women with a follow-up of more than 11 years: [15]

"there was no significant association between calibrated sodium intake and changes in BMD at the lumbar spine, hip or total body, or incident fractures including all, other, and clinical spine sites. Higher levels of sodium intake and intakes above the WHI population median were associated with significantly fewer hip fractures."

This study has the same finding, not showing any correlation between high sodium intake and bone density loss. [16]

Research shows that there is no clear evidence supporting salt intake's correlation with osteoporosis.

"the evidence is based primarily on acute salt-loading studies, and there are insufficient data on the effects of high salt intake on net Ca retention to predict long-term effects on bone health" [17]

This issue remains controversial [18], and more clinical trials are needed.

Stomach cancer

There's evidence suggesting that salt may be linked to stomach cancer, however, this claim is not entirely sure to be true. And it's also not entirely understood how much salt would be required to increase the chance of gastric cancer.

One factor that is proven to increase gastric cancer is the infection of H. Pylori, which causes significant inflammation and damage. H. Pylori is a bacterial pathogen, colonizing roughly half of the world's population. However, an infection of H. Pylori would manifest itself with abdominal pain and burning sensations, nausea and other symptoms.

Salt intake worsens the pathogenicity of H. Pylori, meaning that it'd make the infection have significantly worse consequences. [19]

However, as the study says, it's unclear whether salt intake by itself would increase the risk of gastric cancer, and how much salt would be required to do so.

"The overall results from cohort studies are not totally consistent, but are suggestive of a moderate direct association. Since salt intake has been correlated with Helicobacter pylori (H pylori) infection, it is possible that these two factors may synergize to promote the development of stomach cancer. Additionally, salt may also cause stomach cancer through directly damaging gastric mucus, improving temporary epithelial proliferation and the incidence of endogenous mutations, and inducing hypergastrinemia that leads to eventual parietal cell loss and progression to gastric cancer."

"Several mechanisms by which salt intake may increase stomach cancer risk have been postulated, although to date there has been no consistent conclusion."

"Ideally, dietary modification of salt intake, as well as eradication of H pylori infection, is a promising strategy for gastric cancer prevention throughout the world, especially in developing counties. However, the former strategy is more practical than the latter according to previous epidemiological studies. Future studies that address the association with salt and other dietary factors and the interactions between these factors in different aspects, e.g. molecular level, may help to shed light on the etiology of stomach cancer."

That said, if having a H. Pylori infection, it'd be best to directly treat the infection and address the root cause, rather than simply controlling amounts of salt.

Another study suggests that there would be more factors with salt besides H. Pylori interaction that would cause cancer, albeit still unclear. [20]

"The risk of gastric carcinoma is influenced not only by H. pylori strain characteristics and host genetic determinants but also by environmental elements. One factor that has uniformly been associated with an increased risk of gastric cancer is high dietary salt intake."

"The mechanisms by which salt increases the risk of gastric cancer in humans are incompletely understood. One possibility is that salt may have direct effects on the gastric epithelium that lower the threshold for malignant transformation. Another possibility is that salt damages the gastric mucosa, thereby allowing entry of carcinogens into gastric tissue. Upregulated production of cytokines in response to a high-salt diet may also be contributory. Finally, an intriguing possibility raised by recent observations is that high salt concentrations could potentially modulate gene expression in H. pylori."

The science is still not clear if and how, and in what quantities, salt would actually increase the risk of gastric cancer without H. Pylori.

Conclusions

Taking everything into account, it seems that the big fuss about salt is mostly unsubstantiated.

The recommendations are grossly outdated considering recent strong evidence, and would need a revision--especially when considering that the original recommendations are based on weak evidence (e.g. nine studies, less than 100 people per study with a total of 479 people, and no data to show that salt restrictions reduced mortality).

It's more likely that the correlation between high sodium and increased risk of mortality would actually be because of the type of foods usually containing high amounts of salt themselves, namely highly processed fast foods and meat, rather than the salt itself.

The most likely safe bet for salt is to keep the sodium amount between 4-5g daily, as more than 7g and less than 3g would increase risk of mortality.

Quite a lot of people still eat too much salt in the modern world, basing their diets mainly on salt-rich fast foods. This can be easily mitigated by reducing (or preferably eliminating) fast foods--which are unhealthy for other health risks unrelated to excessive salt consumption as well--and by replacing them with home-cooked-foods.

If struggling to adjust the palate to a lower amount of salt, make use of potassium chloride to substitute some of the salt with a similar tasting compound, without increasing sodium intake, and increasing potassium intake, that some people seem to not reach recommended amounts of.