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.

Tagged as: disease, environment, heart, kidney, macrocosm, metal, nature, salt, Science, water, western research, western-science