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 (including right here). 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.
Despite this utter lack of plausibility, there has been some study of the health effects of an alkaline diet (but not much). A 2016 systematic review of the evidence for an alkaline diet for the prevention or treatment of cancer concluded:
Despite the promotion of the alkaline diet and alkaline water by the media and salespeople, there is almost no actual research to either support or disprove these ideas. This systematic review of the literature revealed a lack of evidence for or against diet acid load and/or alkaline water for the initiation or treatment of cancer. Promotion of alkaline diet and alkaline water to the public for cancer prevention or treatment is not justified.
A 2011 systematic review of alkaline diet for preventing osteoporosis found:
A causal association between dietary acid load and osteoporotic bone disease is not supported by evidence and there is no evidence that an alkaline diet is protective of bone health.
The bone health claim was based on the acid ash hypothesis that the acidity of the diet affects calcium loss from the bones. But this hypothesis is also wrong:
There is no evidence from superior quality balance studies that increasing the diet acid load promotes skeletal bone mineral loss or osteoporosis. Changes of urine calcium do not accurately represent calcium balance. Promotion of the “alkaline diet” to prevent calcium loss is not justified.
I found one exception to the conclusion that there is no plausible benefit from drinking alkaline water, and that is for acid reflux. While a benefit is far from well established, this is the only claim that is at all plausible. Using antacids to acutely treat acid reflux, to buffer the acid in the stomach, does make sense, although the effects should only be very short term. Drinking alkaline water could work just like taking a Mylanta, and there is some evidence to support that.
However – there are no studies of actual efficacy in humans. There is therefore no reason to recommend or use alkaline water for acid reflux over well-established effective treatments.
Therefore – there is no plausibility at all to the claims that alkaline food or water has any general health effect, and in fact there are good reasons from basic biology to conclude that there should be no health effect from adjusting the pH of what you eat (of course, except avoiding strong acids or bases that can burn tissue). Alkaline water is pure snake oil.
Why, then, is the popularity of this snake oil on the rise? As is a common theme here at SBM, there is a triumph of marketing over science and reason. This also represents the power of celebrity over evidence. Celebrities like Tom Brady and Beyonce have been touting the benefits of alkaline water. Add in a little placebo effect, and the public is easy to convince that almost anything works.
There also appears to be something psychologically appealing to magic water. Water has a reputation for being wholesome and healthful, partly because it is essential for life. We are attracted to the notion of pure water, and repulsed by water that is foul or contaminated. These emotions would have an obvious survival advantage in the wild. Pushing these emotions just a little gives us extra-wholesome water with magical healing properties. For this reason there are all sorts of magic water products on the market, and there probably always will be.