Oliver Childs March 24, 2014
Some myths about cancer are surprisingly persistent, despite flying in the face of basic biology. One such idea is that overly ‘acidic’ diets cause your blood to become ‘too acidic’, which can increase your risk of cancer. Their proposed answer: increase your intake of healthier ‘alkaline’ foods like green vegetables and fruits (including, paradoxically, lemons).
This is biological nonsense. True, cancer cells can’t live in an overly alkaline environment, but neither can any of the other cells in your body.
Blood is usually slightly alkaline. This is tightly regulated by the kidneys within a very narrow and perfectly healthy range. It can’t be changed for any meaningful amount of time by what you eat, and any extra acid or alkali is simply peed out in urine.
To maintain the correct balance within the body, your urine can and does change pH, depending on what you’ve eaten (explained in detail in this post). This can be seen by testing urine pH (acidity) after eating different foods and is the basis of the mistaken belief that diet can “make the body alkaline”. But that’s all you’re changing, and anyone who claims otherwise simply doesn’t understand how the body works. [Edited for clarity and extra links, KA 08/08/14]
While eating lots of green veg is certainly healthy, that’s not because of any effect on how acid or alkaline your body is.
There is something called acidosis. This is a physiological condition that happens when your kidneys and lungs can’t keep your body’s pH (a measure of acidity) in balance. It is often the result of serious illness or poisoning. It can be life-threatening and needs urgent medical attention, but it’s not down to overly acidic diets.
We know that the immediate environment around cancer cells (the microenvironment) can become acidic. This is due to differences in the way that tumours create energy and use oxygen compared with healthy tissue. Researchers are working hard to understand how this happens, in order to develop more effective cancer treatments.
But there’s no good evidence to prove that diet can manipulate whole body pH, or that it has an impact on cancer.