Demystifying the Bohr Effect

I breathe too much and I get less oxygen into my muscles? That doesn't sound right, yet it's true.

Well over a 100 years ago Danish scientist, Christian Bohr made the discovery that you need a certain level of carbon dioxide (CO2) in your blood in order to easily use the oxygen (O2) that is pulsated through your body, also in the blood. The two gases rely on each other: carbon dioxide is made when oxygen and carbon combine (one carbon molecule + two oxygen molecules = CO2), and CO2 helps O2 to get into the tissue cells where the CO2 is produced.

When CO2 is a little on the low side, less O2 is released into the tissue cells, and when CO2 is a little on the high side, extra O2 is released from the blood. This is called the Bohr effect.

When CO2 levels drop, which only happens if you breathe out too much of it, then haemoglobin, which carries oxygen around your body, gets sticky and forms a tighter bond with the O2. This means that instead of dropping off the correct amount of oxygen to your muscles, brain, heart and every other part of your body, it is likely to drop off about 10% less.

Low levels of CO2 also narrow your blood vessels, which make it harder for blood to reach your muscles, and so when this is combined with the Bohr effect, it is no wonder that people who over-breathe suffer from a lack of stamina.

Because people are taught they cannot live without O2, they are often also taught that CO2 is both unnecessary and a waste product. In spite of Christian Bohr dispelling this myth in the 1890s, it still persists today. So much so that many people continue to do deep breathing exercises in an effort to force it out of their lungs. If CO2 is really harmful to humans, why are we able to do mouth-to-mouth resuscitation?

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