Alkaline diet

Foods don’t influence our blood pH

Proponents of the alkaline diet have put forth a few different theories about how an acidic diet harms our health. The more ridiculous claim is that we can change the pH of our blood by changing the foods we eat, and that acidic blood causes disease while alkaline blood prevents it. This is not true. The body tightly regulates the pH of our blood and extracellular fluid, and we cannot influence our blood pH by changing our diet. (5, 6) 

High doses of sodium bicarbonate can temporarily increase blood pH, but not without causing uncomfortable GI symptoms. (7, 8) And there are certainly circumstances in which the blood is more acidic than it should be, and this does have serious health consequences. However, this state of acidosis is caused by pathological conditions such as chronic renal insufficiency, not by whether you choose to eat a salad or a burger. In other words, regardless of what you eat or what your urine pH is, you can be pretty confident that your blood pH is hovering around a comfortable 7.4.

A more nuanced claim has been proposed specifically regarding bone health, and this hypothesis is addressed somewhat extensively in the scientific literature. It supposes that in order to keep blood pH constant, the body pulls minerals from our bones to neutralize any excess acid that is produced from our diet. Thus, net acid-forming diets (such as the typical Western diet) can cause bone demineralization and osteoporosis. This hypothesis, often referred to as the ‘acid-ash hypothesis of osteoporosis,’ is what I will discuss for the rest of this article. I’ll address some of the other health claims in part two.

Overall, the acid-ash hypothesis of osteoporosis is not supported by physiology, clinical trials, or observational data.

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