How Alkaline Should Our Bodies Be?

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Much has been made in the media recently about the values and advantages of an alkaline body.

But is this actually true? And how does the introduction of high levels of the alkalising element O2 affect this?

Firstly, a totally alkaline body is neither desirable nor achievable.

For those who’ve forgotten their school chemistry lessons, acidity and alkalinity are measured using the pH scale, which runs from 0 to 14 where 0 is highly acidic, 7 is neutral and 14 is highly alkaline.

The myth that we need to ‘alkalize’ our bodies is based on a fundamental misunderstanding of human physiology. In fact, there are essential life sustaining chemical reactions continuously happening in our blood and they can only happen in a narrow range of pH levels.

Maintaining the right pH level is so important to our survival that if it drops below 7.35 or rises above 7.45 the body deploys numerous buffering mechanisms involving blood proteins, phosphate, bicarbonate, lungs and kidneys in order to restore the balance.

Anything that overwhelms those buffering mechanisms and makes the blood either too acidic or too alkaline would quickly result in death.

One of these reactions is the Bohr effectc, which explains how the haemoglobin’s O2 binding affinity is inversely related both to the acidity of the environment and to the concentration of CO2.

Since CO2 reacts with water to form carbonic acid, an increase in CO2 results in an acidification of the blood resulting in haemoglobin proteins releasing their load of O2. Conversely a decrease in CO2 provokes an increase in pH which results in haemoglobin picking up more O2. So as cellular respiration generates CO2 the body cleverly targets O2 release and CO2 removal.

If a person were to be practicing yoga they might be told to consciously relax any muscle that was not essential to the pose. This is a good example of how the effect works.

Whilst acidity and alkalinity spread in a liquid environment, there will be peaks and troughs in the pH, so as the muscles under stress pump out more CO2 the haemoglobin in closest proximity will be exposed to the increased acidity and replace its O2 load with CO2 to be transported back to the lungs and exhaled.

John Scott Haldane, the father of modern hyperbarics, had already observed the phenomenon but not the machinery or chemistry behind it.

There are other areas of the body that need very specific ranges of pH to function efficiently and healthily. The stomach operates correctly at an acidic pH of around 2, rising to 4 or 5 after a meal. If the stomach becomes less acidic, we absorb less iron from our fooda. The acidity of the small and large intestines (except for the last part of the small intestine, which has a mildly alkaline pH of 7.4) is carefully maintained by various digestive secretions and beneficial gut microbes that produce lactic acid, short chain fatty acids and other acidifying chemicals from the foods we eat. This acidic environment actually prevents the overgrowth of pathogenic (disease causing) organismsb.

This understanding is important when looking at hyperbaric oxygen therapy. The body still needs the fluctuation in acidity to be able to respond and eradicate CO2.

When in a hyperbaric environment breathing pure O2, the plasma is saturated and the volume at the surface that would be used by nitrogen is replaced with O2, and the internal mitochondria of the cell is also saturated which makes more O2 available for the release of energy. This in turn means that more CO2 is released into the blood stream as a product of metabolization.

The high O2 prevalence offsets the increased acidity of the high CO2 levels and maintains the body’s balance and simultaneously allows the available haemoglobin to transport more CO2 out of the system without reducing the availability of O2.

Thus the frequently touted mantra of alkalinity has a certain element of truth but it would be more accurate to say that we must avoid excesses of acidity associated with high metabolising and maintain the pH of the body in the appropriate range thanks to the Haldane/Bhor effect. This is what hyperbaric oxygen exposure facilitates.


a Jacobs & Miles, 1969

b Fallingborg, 1999

c The Bohr effect, first described in 1904 by a Danish physiologist