salt: Ayurvedic and chemistry perspectives

What is salt? Technically, it is what you get when an acid reacts with a base. However, when it comes to salt in our diet, it is synonymous with sodium chloride, NaCl. It is the compound you get when hydrochloric acid reacts with sodium hydroxide (the base). 
Salt was used by humans long before its chemical composition was known. Before sophisticated analytical technologies, like spectroscopy and mass spectrometry were invented to identify the chemical composition of substances, humans had to use their senses to discern different substances. Ayurveda, a healthcare system that originated in India over 5000 years ago, talks about the salt taste as one of the six essential tastes that is necessary in the human diet to support health.
As with pretty much everything else, we have choices when it comes to salt; from the common table salt, to the pretty pink Himalayan salt, to the less visually appealing black salt. All all salts equal when it comes to our health? This article will delve into the nature, types, and nutritive impact of salt as described in Ayurveda, with some chemistry juxtaposition. 

​Salt taste in Ayurveda
One of the fundamental properties of substances as described in Ayurveda is Rasa, translated as "taste" in English. There are six tastes: sweet, sour, salt, pungent, bitter, and astringent. Since everything that was known to humans was perceived through the senses, Ayurveda describes the properties of substances in terms of five perceivable elements called Panchamahabhoota viz. space, wind, fire, water, and earth. The salt taste has the properties of Fire and Water elements and has the following effect on the body:

• Fire and Water being opposites, salt is neither too heavy nor too light
• Can be heating depending on the type of salt
• Stimulates digestion
• Has lubricant action
• Eases gas
• Causes heart disease in excess

​Types of salt referenced in Ayurveda 
There are over ten types of salt that are referenced in the Brihat Trayi, the three authoritative works on Ayurveda. Of these, five types are referenced in all three which indicates they were probably more commonly used. These are Saindhava, Samudra, Sauvarchala, Vida, and Aubhida. 

1. Saindhava salt is referenced in all three texts as being the best type of salt. This is currently understood to be rock salt. Contrary to other types of salts, this salt is cooling and beneficial for the eyes. The excellent review on salts in Ayurveda by N. S. Mooss explains the possible origins and composition of this salt: 

• Can be white or red in color
• Likely from the Sindh area in current Pakistan which is the probable root of the name Saindhava
• There are two hypotheses for what was the source of this salt: from salt mines and/or from hot springs
• Current commercial varieties of rock salt come from the Kohl and Kalabag areas of Pakistan and from Mandi, Himachal Pradesh in India. The former is considerably more pure than the latter (99% NaCl vs 70-80% NaCl).
• Modern commercial rock salt contains salts of potassium, magnesium, and calcium, all at less than 1%. This is also consistent with the chemical composition of several commercial varieties of Himalayan pink salt as determined by mass spectrometry in a paper by Fayet-Moore et al. Note that trace amounts of salts of several elements (including essential, non-essential, and harmful, viz heavy metals) are also present in any salt. But the most abundant metals, other than sodium, are Ca, K, and Mg. 
• Himalayan pink salt is often referred to as rock salt; from a chemistry standpoint, this seems to be reasonable. 

2. Samudra salt is clearly sea salt from the translation of Samudra which means sea in Sanskrit. Sea salt is described as being "not too hot" and heavy. 

• Sea salt, like Himalayan salt, also contains salts of calcium, potassium, and magnesium. 
• A growing concern with sea salt consumption is the presence of micro plastic contamination in several commercial samples, particularly in salts originating in Asian countries. 

3. Sauvarchala salt is a salt that is described as being "sweet smelling, light, and hot". There is significant confusion regarding the chemical composition of this salt. Based on the properties described, Mooss concludes that it may be comprised of NaCl, with some KCl, and sulfates of Na and K. This salt is likely a close relative of what we know today as Kala namak, or black salt. 
4. Vida salt is described as being "sharp, and alkaline, and dark red in color". This variety of salt is also currently shrouded in confusion as to the chemical composition. It is a salt that seems to be synthesized using organic material, probably alma. It is unlikely that there are authentic commercial forms of this salt available today. 
5. Aubhida salt is described as "sharp, hot, bitter, pungent, and alkaline". The origin of this salt seems to be in current Punjab. Mooss postulates that the composition of this salt is similar to Souvarchala salt based on the similarity in properties described. 
​Iodine in salt
​Iodine was introduced in salt in the US in the 1920s when goiter, a disease that causes enlargement of the thyroid gland due to iodine deficiency, plagued a significant percentage of the US population. Natural food sources of iodine are plants that absorb the nutrient from the soil, seaweed, fish, and dairy. However, there are some areas where the soil is depleted of iodine, such as the Great Lakes region in the US. This area was part of the "goiter belt" that catalyzed the introduction of iodized salt.
Iodine is not found naturally in cow's milk, but industrialization of the dairy industry, particularly, using iodine for sanitation and in feed, have resulted in dairy products becoming a significant, albeit highly variable, source of iodine.
So this begs the question: do we need iodized salt? 

• The population that is most at risk for iodine deficiency are pregnant women and vegans who do not get iodine from any of the animal sources mentioned above. 
• The daily recommended dose of iodine is 300mcg/day for pregnant women and about 150mcg/day for others. Iodized salt delivers over 50% of the daily recommended dose of iodine assuming 3-5g of salt intake per day. 
• Therefore, iodized salt may be a good addition if you are at risk for iodine deficiency. 

Conclusion

• Ayurveda considers Saindhava salt to be the best kind. Modern commercial types of salt that seem to be close to this salt from a chemical composition perspective are Himalayan salt. You may also try procuring the more authentic Saindhava salt from Pakistan or Himachal Pradesh. 
• Be aware of micro plastic contamination in modern sea salt. 
• You might want to mix in iodized salt (you can buy iodized Himalayan and sea salt) if you are at risk for iodine deficiency. 
• The key difference between table salt and the Himalayan and sea salts (besides iodine in the former) are the presence of other essential metals such as calcium, magnesium, and potassium in the latter. Although Himalayan salt is touted for the presence of an oddly specific number of minerals (84?), take this with a grain of salt (pun intended). Most of these minerals are present in very low concentrations to make any impact to our daily needs.