Book review: The wisdom of the body

Title: The wisdom of the body (1932, 1939)

Author: Walter B Cannon

Publisher: W.W. Norton & Company, New York

This book is old, but its subject and its message still hold. The book is about homeostasis: how the body adapts to keep things in equilibrium, despite forces that attempt to change the balance. This provides an important lesson to those who attempt to influence the balance of anything in the human body: the body will adapt, making the intervention less effective. A lesson that many do not learn.

What is homeostasis?

Homeostasis is a term used to describe the auto-correcting, self-righting mechanisms by which the body maintains equilibrium of its environment. Like sweating or shivering to adjust body temperature, concentrating the urine when water input is low and peeing too much when we drink a lot. Or the strengthening of muscles and bones with increased use, and the weakening of these structures with decreased demand (a big problem for astronauts, for example). Blood sugar, blood pressure, and the levels of all the salts (sodium, calcium, potassium etc.) are all finely controlled by multiple, interacting feedback mechanisms.

It should be noted that the levels are not regulated to one, unchanging value, as they can be up-regulated and down-regulated, like muscle and bone strength. They are regulated to the level that the body deems appropriate. For example, it is appropriate for your heart rate to go up when you exercise, that is how oxygen delivery and lactate levels are regulated.

Most of us realise that homeostasis (or ‘balance’) is all around us in nature, what we don’t realise is how deep it goes, right down to the single cell and maintenance of the intra-cellular environment.

What does this book tell us?

This is basically a physiology book, but I include it in this series because of what it tells us about our attempts to manipulate physiology. So many times throughout history (and in the present) without do not realising that a) the body might have settled on that level for a good reason (like increased temperature to fight the cold virus), and b) the body will resist any external attempts to change by adapting. In short, our attempts to change human physiology are often simplistic and naïve, and a reflection of our hubris.

Example: calcium for strong bones - a common fallacy

I treat fractures, and patients often ask if they should be taking calcium (in the form of tablets or dairy food) to make the bones heal better. The logic goes something like this: “bones are made of calcium, and healing bones needs calcium, so if I eat more, the bones will heal faster”. This can be thought of as an analogy taken from fertilising plants: they need fertiliser, and if you give them more, they grow faster.

It is not ridiculous, but it is simplistic, naïve and wrong, because it ignores homeostasis. The level of calcium in your blood is finely regulated by many feedback mechanisms involving many organs and hormones. The level “set” by the body is the right one; raise it artificially by intravenous calcium and you may be in big trouble. Trying to raise it by eating more calcium leads to less being absorbed in the gut, and more being excreted in the kidneys (creating kidney stones), until the level is right.

The right level for what? For everything. For every one of the countless bodily functions for which calcium is used, including fracture healing.

The lesson

Ignoring the homeostatic mechanism has led to failed treatments like:

·      Megadose vitamins (that often cause harm, and never cause good)

·      Hormone replacement therapy for menopause (arguably more harm than good)

·      Oxygen supplementation for newborns that lack oxygen (more harm than good)

·      Low cholesterol diets (which don’t significantly change our cholesterol levels)

·      Eating cartilage (chondroitin, glucosamine etc.) for osteoarthritis (which is not caused by a cartilage deficiency)

·      Eating dopamine for Parkinson’s disease (which is due to a lack of dopamine, but the body soon adapts, requiring increasing doses)

·      Taking opioid medication long term (as the body adapts, the effectiveness declines, requiring ever-increasing doses)

·      Taking calcium to treat osteoporosis (which is not caused by a calcium deficiency) does not help, and increases the risk of cardiovascular events.

Social homeostasis

An interesting final chapter in this book compares social structure to the human organism. Biologically, humans have benefited from the division of labour into specialty cells and organs, and from the evolution of communication and supply networks within our bodies, but these have necessitated the complex homeostatic mechanisms described elsewhere in the book. Similarly, our social evolution has seen the division of labour into specialty groups and the construction of similar communication nerve centres and transport arteries. Our social structures and interactions also tend towards a steady state, from the pendulum swings of politics and international relations to the smallest social groups.

It is interesting that the human organism grows to an appropriate size, but the economies in which we live strive for unchecked, unending growth – what in nature is called cancer.

I don’t think social and biological homeostasis are very different. In fact, it could be argued that social organisation is an extension of biological homeostasis; created by the human organism in order to better achieve biological homeostasis (a reliable supply of food, water and shelter).

The bottom line

The book provides insight into the wonderful complexity of the self-righting mechanisms that keep us alive and functioning optimally. Awareness of this phenomenon is often ignored by those attempting to influence bodily functions.