Alkaline Water: Facts or Fad?

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You may have come across marketing claiming that drinking alkaline water offers various health benefits, such as increased energy and reducing the risk of various diseases. Is there any scientific evidence to back up these claims? In this article, we will explore what alkaline water is, what it does in the body, and what the research says about its effects on health.

What is alkaline water?

If you remember any of your basic chemistry, you will know that pH is a measure of how acidic or basic/alkaline a solution is, on a scale from 0 to 14. A pH of 7 is neutral, meaning neither acidic nor basic. A pH lower than 7 indicates acidity, while a pH higher than 7 indicates that the solution is alkaline or basic.

Drinking water comes out of the tap with a pH close to neutral, usually between 6.5 and 8.5. However, some companies produce branded bottled water treated to achieve a specific pH in the alkaline range, usually between 9 and 10.

What does alkaline water do?

One claim that you may have seen about alkaline water is that it helps adjust the pH in your body to a more favourable value. However, the evidence doesn’t really support this claim. The pH throughout most of our body is tightly controlled and kept within a very narrow range – between 7.35 and 7.45. This is ideal for many biological reactions and processes, including oxygen transportation, and any deviation from this range has serious health implications. Individual cells have multiple ways of controlling their own acidity, while the kidneys can quickly eliminate excess acids or bases from the body. There’s no evidence that drinking alkaline water has a meaningful effect on the pH of the blood or within your cells.

It does appear that alkaline water can buffer stomach acid and raise its pH to some extent. However, this effect is not long-lasting, as the stomach will produce more acid to maintain its ideal pH. There’s also not really any reason a healthy person would want to raise the pH of their stomach – low pH is necessary for proper digestion.

There is some evidence that pH might affect how rapidly water is absorbed. In the gut, water is absorbed via specialised protein channels called aquaporins. Protein function is very sensitive to pH (we’ve all tried the acidic lemon juice in milk thing) and alkaline environments seem to increase the permeability of the aquaporins, allowing water molecules to pass through them at a higher rate.

Purported health benefits of alkaline water:

Hydration:

Based on that last point, you could expect that alkaline water might at least hydrate you better than lower-pH water. However, not all of the evidence agrees, and much of the evidence comes from high performance athletes, for whom the impact of faster water absorption would be much more consequential. Even then, the impact of the quantity of water you drink is going to be much higher than the rate at which that water is absorbed.

pH Control:

But wait, didn’t we already establish that the pH of the water you drink doesn’t affect the pH in your body? We did, and that’s still true in most cases, but there may be an exception in the case of high intensity exercise. Vigorous exercise produces lactic acid and carbon dioxide, both of which lower the pH of the blood. This is enough to lower blood pH significantly (though the body’s pH regulating systems increasingly compensate for this as exercise continues). It is possible that drinking alkaline water while exercising might have a meaningful performance impact by buffering this increased acid production. While there’s some evidence to support this for high intensity exercise, we need more of it.

Disease prevention and anti ageing:

Many sellers of alkaline water claim that it can reduce the risk of various diseases including cancer, and even slow the ageing process. However, there’s very little good quality human evidence behind any of these claims. Proponents often cite anti-oxidant effects as the source of alkaline water’s benefits. While there is evidence to suggest that alkaline water protects isolated cells from oxidative damage, that’s very different to a human clinical trial showing that alkaline water reduces the risk of a specific disease.

Some also claim that alkaline water benefits people with acid reflux. A decade-old study proposed this based on alkaline water’s ability to buffer stomach acid and neutralise pepsin, the stomach’s main digestive enzyme. There are instances of alkaline water seeming to relieve reflux symptoms in very uncontrolled tests, but it doesn’t appear that any clinical trials have been carried out.

It’s worth noting that ‘natural’ alkaline water is the result of water flowing over rocks and picking up minerals such as magnesium, calcium and potassium. There may be some benefit to such water due to these minerals, but this has nothing to do the water’s pH, and is nothing that can’t be achieved through diet or supplementation.

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So, there may be some benefits to alkaline water, but the evidence is pretty weak currently. Unless more evidence emerges, you’re probably much better off just drinking more water. Unlike alkaline water, there is actually some evidence that higher fluid intake is associated with slower ageing.