The Story of Salt: Our Relationship with Sodium Chloride

The Profound History of Salt

Salt's significance is deeply rooted in human history and biology.
Pliny the Elder noted that Roman legionnaires were paid in salt cakes, giving rise to the term "salary" from "solarium."
The "covenant of salt" is a common theme in Eastern and Western religions, signifying important deals and friendships through the exchange of valuable salt.
Da Vinci's The Last Supper depicts Judas Iscariot knocking over a salt cellar, symbolizing an ill omen. Spilling salt is often associated with bad luck, leading to the practice of throwing a pinch of salt over the left shoulder.
In British India, an inland salt hedge was constructed to collect salt taxes, demonstrating the economic value of salt.

Salt has significantly influenced our socioeconomic development and civilizations.
This influence likely stems from salt's critical role in human biology.

Homer Smith, a physiology professor at NYU, proposed that our biological relationship with salt enabled our evolution from marine creatures to humans.
His 1953 book, "From Fish to Philosopher," explores this thesis.

The transition from marine to terrestrial life presented a significant challenge regarding salt acquisition.
Marine environments provided abundant salt, while terrestrial environments made salt scarce and geographically isolated.
This scarcity created a biological imperative to develop strategies for seeking, ingesting, and retaining salt.
Organisms that evolved these strategies survived, while those that did not perished.

Biological salt refers to salt in solution, composed of sodium (Na^+) and chloride ($$Cl^-$) ions.
It has three key functions
- Controls blood pressure by regulating water retention in blood vessels.
- Underpins the electrical activities of our nerves.
- Enables muscle contraction (including the heart).
Imbalances in salt levels can lead to severe illness.

The gut evolved as an efficient salt extraction system, absorbing nearly all ingested salt.
The kidney filters blood, removing toxins while retaining salt.
The brain developed behavioral patterns to sense the need for salt and trigger salt-seeking behaviors.
Taste receptors on the tongue allow us to differentiate salty foods.
Salt-seeking behaviors are linked to pleasure centers in the brain, similar to those affected by recreational drugs.

Professor Smith's hypothesis suggests that our need for salt has driven the evolution of our DNA to maintain salt balance.
The kidney excretes excess salt, maintaining the necessary amount for biological processes.
Imbalances in salt intake and excretion can lead to health problems.

Historically, daily salt intake was around 0.5 grams, which is what we need to survive.
Current recommendations from the World Health Organization (WHO) is 5 grams a day and UK is 6 grams a day.
Modern salt intake often exceeds these recommendations, with many individuals consuming around 8-8.5 grams a day.

High salt intake disrupts salt balance, placing a burden on the kidneys.
Excess salt is stored in the bones and skin.
This leads to widespread hypertension (high blood pressure), recognized by the WHO as a major global health crisis.
Hypertension affects all societies and socioeconomic classes and increases the risk of heart attack, stroke, and kidney disease.
By 2025, it is estimated that 1.5 billion people will have hypertension.

Research focuses on identifying genes that contribute to salt-related health problems.
Mice studies demonstrate that high-salt diets quickly raise blood pressure.
The same genes that regulate salt retention in the kidney and gut are also involved in brain pathways and taste perception.
Two potential solutions are: changing genes (currently not feasible) or changing our environment (diet).
Studies show that reducing salt intake lowers blood pressure in both mice and chimpanzees.

A study where individuals tried to reduce their salt intake after measuring it showed little success.
Participants found it challenging to lower their salt intake significantly.

Food traffic light systems provide information about salt content but are often overlooked.
Many foods contain high levels of salt, with even seemingly healthy options contributing significantly to daily intake.
Individuals have a personal responsibility to be mindful of their food choices and salt consumption.
Governments play a role in collaborating with food industries to reduce salt content in food products.
The UK government has successfully removed 22,000,000 kilograms of salt from food through cooperative policies.
New reduction targets are being set to align with WHO recommendations.

Become salt aware and choose low-salt options when purchasing food.
Consult resources like CASH (Consensus Action on Salt and Health) for advice on preparing low-salt meals.
Reduce salt intake, shifting from a situation where salt was a rare commodity to one where it poses a health risk.