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Season 1, Episode 4

Alkaline Diets

Can eating an alkaline diet help prevent cancer and other diseases?

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One pop-culture food myth is the alternative health belief that cancer and other diseases are caused by your body being too acidic, and that you can prevent them by eating a more alkaline diet.

The pH scale measures the acidity of aqueous solutions, like your body. It goes from 0 to 14. Pure water is neutral and has a pH of 7. Values less than 7 are acidic; values greater than 7 are alkaline. Rain averages slightly acidic, about 5.2; the ocean is slightly alkaline at 8.1; and the human body is right in between at 7.4.

Here's the basic problem with the alkaline diet. Its fundamental assumption, that you can change your body's pH level by changing what you eat, violates everything we know about the chemistry of the body. Your body always stays at 7.4, because the enzymes that trigger virtually every chemical reaction in your body only work in a very narrow range. If your body actually became even slightly acidic or alkaline, you would die very quickly.

Your body's main mechanism for regulating its pH level is your respiration. We exhale carbon dioxide, which comes into your lungs right from the blood. If your blood becomes even slightly acidic, you'll exhale more CO2; if it becomes alkaline, you'll exhale less. This is both rapid and effective; the slow metabolization of food can't compete with the respiratory system's fast and powerful response to changes in pH.

Your kidneys handle the rest of it, removing acids or bases from your blood as needed. The pH of your urine can be all over the place, depending on what was removed from your blood. Urine is the only bodily fluid whose pH can change based on what you eat. Some marketers of alkaline diets take advantage of this by fooling customers into buying urine pH test kits, hoping to trick you into thinking your urine's pH reflects your body's pH. It doesn't.

So what happens when you drink alkaline water or eat an alkaline diet? Nothing. Your stomach, full of hydrochloric acid, is extremely acidic. As soon as the food moves to your intestines, pancreatic secretions bring it back up to 7.4.

All this means the belief that an acidic body is the cause of cancer and other diseases is pure fiction. If anyone tells you that, don't listen to anything else they say. They need to revisit high school biology.


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Carroll, T. "Alkaline Diet". RationalWiki, 27 Dec 2016. Web. 31 Dec 2016.

Farrell, S. "The Alkaline Diet: Help or Hype?" Eat Better. The Cooper Institute, 1 Nov 2016. Web. 31 Dec 2016. <>

Lower, Stephen. "Ionized and Alkaline Water." Water Pseudoscience and Quackery. AquaScams, 11 May 2009. Web. 14 Jan. 2010. <>

Mirkin, G. "Acid/Alkaline Theory of Disease Is Nonsense." Quackwatch, 11 Jan 2009. Web. 31 Dec 2016.

Orac. "Your Friday Dose of Woo: Acid, Base, or Woo (Revisited)." Respectful Insolence. ScienceBlogs, 8 Jun 2007. Web. 31 Dec 2016.