Steven Novella
October 31, 2018

Alkaline water is pure BS – there is no plausibility to the claims of any health benefits, and what evidence we have is negative. Its popularity grows despite this.

From The Guardian:

"According to data from the Beverage Marketing Corporation, a research and consultancy group, the alkaline water market has grown from being a $47m business in 2014 to a $427m business in 2017. It’s projected to be worth $687m by the end of 2018."

Over this same time there has been a slew of popular scientific articles explaining exactly why alkaline water, or an alkaline diet, is pseudoscience. The basic science is pretty straightforward, and even a grade-school understanding is enough to conclude that alkaline water is snake oil.

From a chemical point of view, an acid is any molecule that can donate a proton or accept an electron pair in a reaction. A base (something that is alkaline) is the opposite – it can accept a proton or donate an electron pair. Acids and bases therefore neutralize each other. The measure of how acidic/basic a substance is is pH, with 7 being neutral, <7 being acidic, and > 7 being basic. This is also a logarithmic scale, so a pH of 5 is ten times more acidic than a pH of 6.

Water (H2O) usually has a neutral pH, but water dissociates into H and OH ions. Hydrogen ions are acidic, and OH ions are basic. The number of such ions in pure water is usually small, partly because they react with each other to form back into H2O. So what is alkaline water? Real alkaline water has something in it to make it basic, such as baking soda. Some products claim to alkalinize water electrically, but again any ions in the water will quickly neutralize themselves – pure water will always tend toward a pH of 7.

Now here is where the real pseudoscience comes in – the notion that you can benefit your health by eating or drinking alkaline food or water. The claim is that the when the body becomes too acidic this causes a host of health problems, and you can fix them by simply balancing the acidity with alkaline water. The problem with this claim is that it is extremely misleading.

The body maintains a very narrow pH (7-7.4), which is the range at which the chemical reactions that keep us alive are optimal. If the pH strays outside this range, you will indeed become acutely ill. For this reason animals have evolved a host of powerful mechanisms to keep the blood and tissues within this very narrow pH. For example, our kidneys will produce urine that is more or less acidic to help balance pH.

Also, since carbon dioxide is acidic, we can maintain a specific pH in the blood just by varying how much we breathe and blow off CO2. In fact, our respiratory rate is determined primarily by the amount of CO2 in the blood – not oxygen. The concentration of CO2 can be adjusted moment to moment, and of course occurs involuntarily without our conscious input.

These mechanisms for maintaining a narrow range of pH (in a healthy person) overwhelm the effect of whatever you eat or drink. The only exception to this are serious acute medical conditions that affect pH, or consuming poisons that affect your pH. Consuming regular food and liquids, regardless of their pH, will simply not affect the pH of your body. Therefore the entire premise of an alkaline diet or alkaline water is pure BS, nothing but pseudoscience.