Salt Sensitive Hypertension and Classical Chinese Medicine, Part 3

This is the final post in a three part series by Brandon Brown, blogger and student of Classical Chinese Medicine at NCNM. You can read the first two parts here and here, and can read references for the article by visiting Brandon’s site here.

Salt in the Classics

Salt is mentioned a number of times in the classics. In the Neijing Suwen, salt is considered the flavor of the Kidney. But what does this mean exactly? What follows are the most descriptive and instructive references from the Suwen followed by my translations.

Chapter 67
北方生寒，寒生水，水生鹹，鹹生腎，腎生骨髓，髓生肝。其在天為寒，在地為水，在體為骨，在氣為堅，在藏為腎，其性為凜，其德為寒，其用為，其色為黑，其化為肅，其蟲鱗，其政為靜，其令，其變凝冽，其眚冰雹，其味為鹹，其志為恐。恐傷腎，思勝恐，寒傷血，燥勝寒，鹹傷血，甘勝鹹。

“The north generates cold, cold generates water, water generates salty, salty generates kidneys, kidney generates the marrow, marrow generates the liver. In heaven it is cold, on earth it is water, in the body it is bone, its qi is hard, in the Zang it is the Kidney, its nature is cold(shivering), its virtue is cold, it is “use”, its color is black, it changes into solemn-ness(seriousness), it is worms and fish-scales, its government is stillness(jing), it causes, its pathological change is congealing coldness, its natural disaster is ice hail, its flavor is salty, it is will by fear. Fear impairs the kidney, thought defeats fear, cold damages blood, dryness defeats cold, salty damages blood, sweet defeats salty.”

Chapter 3
味過於鹹，大骨氣勞，短肌，心氣抑。
Excess salty flavor, causes great hardening of bone Qi, shortens the muscles, and restrains heart Qi.

Chapter 5
鹹勝苦。
Salty defeats bitter.

Chapter 10
是故多食鹹則脈凝泣而變色。
Therefore, much eating of salty makes the pulse concrete and the color changing.

Chapter 22
心欲耎，急食鹹以耎之，用鹹補之，甘寫之。
The Heart desires softness, anxious people eat salty that softens it, use salty to mend it, sweet drains it.

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These excerpts from the Suwen indicate the myriad functions of salt. In Chinese Medicine, the Salty flavor is typically used to soften nodules as mentioned in Chapter 22, but we also see in Chapter 3, 10, and 67 that salt can pathologically also create hardness of Bone Qi, restrain Heart Qi, damage blood, and cause the pulse to be very firm. We can read these lines in typical Chinese Medicine fashion: that as a remedy, the salty flavor has a purpose in softening nodules, in moderation salt perhaps allows the Kidney to perform its function of storing, but pathological excess consumption of salt can lead to sclerosis.

In Chinese Medicine, the 5 flavors that go with the 5 organs typically counteract the nature of the targeted organ. For example, the energetic nature of the Liver is up and out whereas the flavor Sour astringes and contracts. The Heart, the fire organ, is up and bitter is down. For the Lung, its nature is contracting down and in, whereas pungent is the opposite: up and out. For the Kidney, as we see in Chapter 67 above, the energetic nature is definitely to store by freezing. Salt, must counteract this freezing nature, as we know that it does from our experience: salt both reduces the freezing point of water and raises the boiling point. The presence of salt liquefies ice, and thus can soften hardness (tumors, goiter, etc.). But because salt has an affinity with the Kidney it counteracts the storing nature of the organ, liquefying the Kidney energy (perhaps Jing) to be used in the body as Qi. Therefore we see again that, salt pushes out from the inside.

In their paper on the Classical Energetics of the Five Flavors (find in references section), Arnaud Versluys and Jessica Atkins describe the therapeutic actions of the five flavors in terms of tonification and purgation. In cases of excess or deficiency, the organs can be respectively purged or tonified with the appropriate flavor as shown in the figure below.

Figure 2: The actions of the 5 flavors

Organ: Excess of, purge with : Deficiency of, tonify with
Fire : Sweet : Salty
Earth : Bitter : Sweet
Metal : Pungent : Sour
Water : Salty : Bitter
Wood : Sour : Pungent

According to their interpretation, the salty flavor purges excess in the Kidneys and tonifies the Heart. In the case of SSH, chronic overexposure to dietary salt may act medicinally and impair or purge the storing function of the Kidney and thus over-tonify the Heart. Because the Kidney is also said to store pre-natal essence if there is no pathological influence to expel in the Kidneys, it is possible that what is purged is actually pre-natal essence (Jing). This essence is circulated throughout the body, transformed to Qi by the Liver function, and transformed and stored as Shen by the Heart. Shen, and thus consciousness, have as a substrate the brain, but Shen is housed in the Heart.

Therefore, the use of salt habitually may increase the Jing-Qi-Shen generation cycle, which makes us sharp and awake, but has the detrimental effect of possibly depleting pre-natal essence if the Kidneys are not constantly tonified. In the Suwen it mentions that at 8 times 7 years (56 years old), the hair (ruled by the Kidney) turns gray and the signs of aging begin to become visible. “The kidneys’ ability to excrete sodium declines gradually with age. If, with age, salt consumption is not reduced, sodium balance is maintained by raising fractional sodium excretion, which requires elevation of BP” (Khalil 2005). The accumulation of salt in the ocean over the years has begun to take its toll.

Because purgation of the Kidney in a non-pathological condition also tonifies the Heart, an interesting consequence of excess in the Fire element is that it easily overflows onto its child organ, the Earth. This would lead the Earth to become overwhelmed and thereby inhibiting it to control the Water element, whose function is diminishing due to the natural processes of aging. In CM, we say that the “Earth rules the muscles” and in the SSH case this clearly relates to the smooth muscle of the vasculature losing its ability to contract. Due to an excess in the Heart domain, the smooth muscle becomes dry, stiff, and brittle. The patho-mechanism of this is illustrated below.

The standard American diet is predominantly made of the flavors salty and sweet. The overwhelming absence of bitter (with the exception of Shen disturbing coffee and beer) and the overwhelming abundance of salt and sugar in the standard American diet may explain the danger of increased exposure to dietary salt.

Conclusion

It is not surprising that decreasing daily dietary salt intake will help in treatment SSH. However, what we learn from the classics and the physiology of salt in the body is that Kidney tonification is essential for SSH.

Because the Earth element has become so affected by this chronic exposure to salt, purging the Earth of excess with the bitter flavor will be important. Like a lone neuron in the brain, salt consumption is entangled in the higher social structures that predominate our times: working long hours, using the mind instead of physical labor for generating a living, exposure to a barrage of psycho-sensory information in terms of television, music, and people, along with increasing anxieties about all of it. Seen in this context it really is no wonder why SSH is a modern disease of the “developed” world.

Brandon Brown

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September 11, 2008 · Filed Under Classical Texts (general), Hypertension, Science, Theory

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Salt-sensitive hypertension and Classical Chinese Medicine, Part 2

This is the second part in a three part guest article series by Brandon Brown, student at National College of Natural Medicine and Chinese medicine blogger. You can access the first part of the article which covers salt in the macrocosm - nature. I should note that he has posted references for the entire series on his blog, you can access those references by clicking on this link. -Eric

Salt in the Microcosm

By preserving meat with salt, mankind was unknowingly creating a vicious cycle that would change the health of all people up to the present day. It is estimated that before the advent of this preservation technique people consumed no more than 0.5 grams of naturally occurring salt per day (g/d). After brining was put to use, daily consumption jumped to an estimated 10 g/d (because even though the meat is soaked in water to reconstitute it, no amount of soaking can remove a large amount of salt). This continued to climb throughout the centuries, upwards to nearly 18g/d (some estimates in Scandinavia indicate consumption near 100g/d) until the advent of refrigeration techniques which brought estimated consumption back down to its present day levels of 10 g/d. It is hypothesized that one reason for the stabilization at 10g/d instead of 0.5g/d is the addictive nature of salt: in the presence of continued salt loads the taste receptors on the tongue down-regulate their sensitivity to the salty flavor. However, as we will see, salt plays a crucial role in the nervous system, and it could be this current cultural bias for all things cerebral that creates our hunger for the briny crystal.

One of the most prolific cellular mechanisms in the body is the sodium-potassium pump. These pumps are found in a number of cells throughout the body, but most importantly in the nerve cells of the Central Nervous System. This mechanism, called Na+/K+-ATPase, regulates cellular chemistry and polarity by using ATP to remove 3 Na+ intracellular ions and replace them with 2 K+ ions. Na+/K+-ATPase is the mechanism that is responsible for the nerve’s ability to achieve the resting potential of approximately -70 mV by removing a net positive charge from the intracellular fluid with each pumping action. The creation of this potential primes the neuron to do work, in this case to release its charge as a rush of electrochemical ions, creating a signal that releases neurotransmitters at the terminal end of the neuron. The charging of this battery comes at a cost of a single phosphate group from ATP (converted to ADP). Because the pump is operating against the normal flow of the concentration gradient, energy is required to create this potential difference. This process is such that a large differential between sodium and potassium is created:

Table 1: Concentration of fluids by ion type (mmol/L)

Ion	Extracellular	Intracellular
Na+	150	15
Cl-	110	7
K+	5	150

Therefore the exterior of the cell is essentially salt water (NaCl), and the interior of the cell is largely dissolved potassium ions.

This is striking for a couple of reasons. First, in the resting state we see that salt water is kept on the outside of the membrane and only when an action or graded potential occurs is it allowed to rush into the cell. To reach the resting potential the cell must actively store potassium, and excrete sodium. In other words, the movement of salt (in this case sodium) into the cell causes the transmission of an electrochemical action potential. It is this action potential that is thought to give rise to all cognition and movement in the body. The axon, the long transmitting portion of the neuron, propagates the signal through voltage controlled sodium channels. The inward movement of salt is giving birth to movement and thought, whereas the expulsion of salt promotes stillness and thusly, stores great potential.

Secondly, the regular and crystalline lattice structure is perhaps more than metaphorical. In cognitive neuroscience, most theories of the mind involve describing the geometrical structure of the neural lattice as an explanation of functional capabilities. For example, the visual cortex is organized in columnar functional groups that serve to detect edges in the visual field. The creation of memory involves creating a new pathway on an already established lattice. Therefore, as sodium enters the cell it gives its organizational properties over to the cell to provide for the creation of new synaptic connections and lattice-like structures. The lattice-like structure of the salt is reflected in the lattice-like structure of the brain.

Figure 2: Columnar structure of neurons in the visual cortex and the octahedral geometry of sodium chloride

In terms of SSH research, it seems that excess dietary salt may not only change the sodium levels in the plasma but also in the cerebrospinal fluid, inhibiting Na+-K+-ATPase in both locations, perhaps giving rise to cognitive changes (Khalil 2005).

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In the next and last installment of this series, Brandon discusses salt from the perspective of Classical Chinese texts and brings the various ideas together. Please look forward to it tomorrow. -Eric

September 10, 2008 · Filed Under Hypertension, Science, Theory

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Salt-sensitive hypertension and Classical Chinese Medicine, Part 1

Editor intro

This is a Guest Post by 3rd year Classical Chinese Medicine student (and Chinese medicine blogger) Brandon Brown. Brandon is a friend of mine and an excellent student. He approached me with this paper and I immediately knew it would be a fantastic contribution to the site as many folks have asked me for rigorous examinations of the cross-pollination between Western and Chinese science as expressed in medicine. This will be a 3 part series released over the next 3 days, please feel free to leave comments - Brandon is a regular reader of the site. I should note that he has posted references for the entire series on his blog, you can access those references by clicking on this link. -Eric

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Author intro

The following three posts are from a paper I wrote in the Winter of 2008 for Dr. Edward Neal’s Clinical Physical Diagnosis course at NCNM. It is my attempt to apply classical Chinese medical knowledge to a modern disease processes that is pervasive, salt-sensitive hypertension. In looking at all modern diseases, I believe it is extremely beneficial as CCM practitioners to understand the patho-mechanism as presented to us by current research in Western materialism. Because yang (energy) leads and yin (substance) follows, by knowing the yin we can garner important clues that can allow our yang treatments to strike with more clarity, force, and efficacy. I welcome your thoughts and comments. - Brandon

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Salt-sensitive hypertension : Western science and the macrocosmic view

“The highest good is like water, it settles in the lowest place where people do not like to be.”

Dao De Jing

It is estimated that salt-sensitive hypertension (SSH) accounts for over two-thirds of people over 60 who have primary hypertension . Though there are genetic variants to the tolerance of the amount of salt that effects hypertension, dietary sodium is considered the most important environmental influence. This begs the question: why are some people who are hypertensive experience a salt sensitivity and others do not? The answer to this question may lie in the theories of Chinese Medicine and in the fundamental nature of salt, and its relationship to water and the Kidney. I will first give a summary of hypertension in western terms and discuss current research theories. Following this, I will discuss salt: cultural symbology, the natural formation, and specific references in the medical classics. By so doing, I hope to show how an ancient medicine sheds important light on this modern disease, through the connection of the Kidney and the Heart.

Hypertension - a more Western perspective

Primary hypertension is defined as chronically elevated blood pressure where systolic arterial blood pressure consistently exceeds 140 mmHg or greater. To be considered primary, the hypertension must be idiopathic, and not due to secondary factors such as kidney disease or adrenal tumors, for example. Primary hypertension is considered to be a major risk factor for strokes and cardiovascular disease, and is a leading cause of chronic renal failure . Heart disease is the number one killer in the United States, leading to well over half a million deaths per year.

It was observed in a strict rice and low-sodium diet study performed in 1944 that patients with kidney disease and hypertension were able to lower their blood pressure by as many as 100 mmHg in some cases . Current theories of the pathological mechanism of SSH posit abnormalities in renal sodium transport in the nephron structure of the kidneys . The cause for these kidney abnormalities are thought to be caused by both genetic and environmental factors. Because salt generally attracts water through osmosis, increased blood sodium not excreted by the filtering mechanisms in the kidney causes an increase in the water content of the blood, thereby causing the vessels to swell. This increased swelling, is an increase of “total peripheral resistance of the vasculature”, and is thought to create a long-term load on cardiac output ultimately leading to heart failure. Therefore, we can say that the presence of salt in the blood pushes out from the inside. This is contrary to the renin-angiotensin mechanism of the Kidney, which vasoconstrics and thus pushes in from the outside.

Salt in the Macrocosm

“Ye are the salt of the earth; the best of the human race.”

Jesus Christ in Matthew 5:13

The creation story of salt begins with fresh water falling from the sky as rain, and landing on the elevated earth. The nature of water is to always seek the lowest point of any terrain. The rain water falls on the hills at first as drops, which coalesce to form a trickle, which then join to form streams and these eventually join to form massive rivers, which empty into the sea. On this journey, constant erosion takes place as minerals are stripped from the earth and mountains and carried to the ocean. Because of its polar nature, water acts as a solvent to all matter. Place any material in water, and given enough time, transformation will occur. Metal will rust, vegetation will decay, and other liquids will eventually diffuse and become one with the water. The mineral rich streams, which still taste like fresh water to us, empty into the vast oceans that today are heavily salted and totally unpalatable, even though they are only 3.5% salt . The oceans continue to accumulate more and more salts because over millions of years evaporation extracts the water from the ocean, but not the minerals. The minerals are too heavy and earthbound to be steamed up to the heavens. This process is depicted in Figure 1.

Figure 1: The generation of saltwater

Of special interest in Figure 1 is how it reflects the generating cycle of the 5 Phases (五行). That is, Water falls from Heaven onto Earth and Metal, flowing down to Water, where through the energy of Fire, the fresh water is evaporated upwards toward heaven by the process of Wood. What is left behind is a storehouse of salt. Because of this, we would expect to find that places of warmer climate would have oceans with higher salt content. This is in fact the case, as places such as the Mediterranean Sea have a much higher salinity than that of cold water oceans (the Arctic and Northern Pacific, for example).

Salt is very much a dissolved solid from the Metal sphere. It is highly organized and crystalline, and looks almost identical to ice (Figure 2). Salt was the first currency of the civilized world, due to its value as a preserver of meat. As Richard Manning writes in Against the Grain, it was the ability to preserve and store meat which essentially lead to the creation of wealth and signaled the shift from nomadic hunter-gatherer societies to those of sedentary agrarian caste systems. Earlier than 800 A.D., the Yellow Emperor himself is said to have fought the very first war over the precious commodity . In 450 B.C., iron was put to use to boil sea water in huge pots to extract salt, a method that was used for the next 2000 years. By expediting the evaporative process, larger amounts of salt could be garnered more quickly and thus a greater amount of wealth could be amassed. Even in these ancient times salt stored, or preserved, wealth. To this day, the word “salary” comes from the Latin “salarium”, or “to be payed with salt.”

Not surprisingly, then, salt as a symbol of wealth came to symbolize all that is good. It is common practice to throw salt over the shoulder to ward off the devil, sumo wrestlers throw salt in the wrestling ring to purify it before a match, and placing piles of salt in tombs purifies the soul’s journey from earth to heaven, for example. Throughout history and across the world, in almost every culture, salt has been used in religious, medical, and cultural contexts to purify and clean the soul and the body from evil and disease . Ultimately, however, it is argued that salt is a often a cultural metaphor for semen, and the essence of man.

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In the next article in this three part series, Brandon will dive into the microcosm - discussing the mechanisms above as they reflect into the human body. Look for it coming soon.

September 9, 2008 · Filed Under Hypertension, Science

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