Claims that it has various health benefits have helped increase the popularity of alkaline diets and sales of machines that turn water alkaline.
Ionizing machines are one example of these products. These can cost over a thousand dollars.
But what scientific evidence lies behind drinking alkaline water? Are there any proven health benefits?
What is alkaline water?
The pH of water is neutral, around pH 7. Chemicals and gases can change this to make it more acidic or more alkaline.
The pH of water is around 7, but some people say it may be more healthful to drink water that is alkaline.
Rainwater's pH is slightly below neutral, because there is carbon dioxide from the air, and this increases acidity.
- Acidic substances have a pH of below 7.0, down to zero. The pH of vinegar is around pH 3, lemon juice around pH 2, and battery acid around pH 1.
- Alkaline substances have a pH up to 14. Baking soda's pH is between pH 8 and 9, and milk of magnesia is between pH 10 and 11.
Water can be high or low in pH, but if it is too high or too low, it can have adverse effects.
Water that is too alkaline has a bitter taste. It can cause deposits that encrust pipes and appliances. Highly acidic water may corrode metals or even dissolve them.
Alkaline water has become popular in recent years due to a belief that it may benefit health.
Bone health and osteoporosis
Some research has been done on the effects of alkaline intake on bones. A study published in Bone found an effect on bone resorption. Bone resorption is the process where old bone cells are broken down and replaced by new ones.
Less bone resorption and more mineral density result in better bone strength.
The authors concluded that "a bicarbonate- and calcium-rich alkali mineral water decreased bone resorption more than a calcium-rich acidic mineral water."
However, this was a small effect.
The scientists called for more research, to see if the benefit of less bone resorption was long-term and could improve bone mineral density.
Another study, published in Nutrition Journal, compared the impact of an acidic diet, rather than alkaline water, on osteoporosis, a disease marked by weak and brittle bones.
Reviewing the background to the study, the authors noted a high number of claims being made on the Internet. These claims suggested "that alkaline diets and related commercial products counteract acidity, help the body regulate its pH, and thus prevent disease processes."
The review used high-quality evidence to conclude that acid from the modern diet does not cause osteoporosis. It also concluded that an alkaline diet or alkaline supplements or salts do not prevent osteoporosis.
However, the researchers did not expect this to reflect total calcium levels, and they found no evidence that this would improve bone health or help prevent osteoporosis.
A review of the effects of alkalis on cancer was published by Dr. Tanis Fenton and colleagues in the journal BMJ Open.
The review assessed thousands of studies, but the authors found only one proper, randomized test of acid in the diet and cancer of the urinary bladder.
They found no studies about alkaline water and cancer in humans.
The researchers note: "In our experience, patients with cancer are approached by salespeople who are promoting water alkalinizers as a way to treat their cancer."
"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."
Acid reflux disease is when the contents of the stomach, which are acidic, splash back up the food pipe.
Acid reflux that keeps happening for a long time can cause damage and a disease known as gastroesophageal reflux disease, or GERD.
A study published in Annals of Otology, Rhinology & Laryngology found that drinking alkaline water might be worth further study as a supplement to other treatments for reflux disease.
It found that alkaline water at pH 8.8 stops an enzyme that is connected to reflux disease. It also appeared to reduce the acidity of the stomach contents.
The work was done in a laboratory rather than in humans. More research would be needed to support these findings.
Moreover, stomach acid exists for a purpose. It kills bacteria and other pathogens, and it helps our bodies to digest food and absorb nutrients.
Blood pressure and diabetes
However, the scientists point out that participants had different measures of whole blood viscosity at the outset, which could have affected the results.
It is worth noting that the study was sponsored by Essentia Water, who also provided the alkaline water used.
Recommended daily intake
As there is no evidence to support the health benefits of alkaline water, there is no recommended amount that improves health.
However, if you wish to start drinking alkaline water, start with a low intake and increase it gradually. This can reduce the corrosive effects of highly alkaline water.
What is the alkaline diet?
The alkaline diet, said Fenton's study, is promoted to correct "the acid state that the modern diet creates."
It includes more fresh fruits and vegetables and reduced protein intake.
"The marketing of the alkaline diet promotes not only a diet, but also the sale of related supplements and water alkalinizer machines through almost every media medium, including websites, books, and videos," the authors wrote.
A review published in the Journal of Environmental and Public Health concluded that an alkaline diet may have some benefits.
Fruits and vegetables, say the researchers, have a negative acid load that could improve the balance between sodium and potassium, with possible benefits for bone and muscle health. This could help prevent high blood pressure, strokes, and other chronic diseases.
Children with severe metabolic acidosis tend to have low levels of growth hormone, and this can lead to short stature. An alkaline diet may help to reduce problems related to low growth hormone in those who are susceptible.
However, none of these findings relate specifically to alkaline water.
A study published in 2016 looked at the effect of consuming alkaline water on 150 mice over a period of 3 years.
Results suggested that those who drank alkaline water had signs of greater longevity, in other words, they aged less and were more likely to live longer.
No significant differences were seen in the heart, liver, kidneys, brain, or intestine of the groups studied, and no damage occurred, but there were differences in how the mice and their organs aged.
Does alkaline water promote weight loss?
Alkaline water has shown no benefits for general health and metabolism.
While it will not add calories as part of a balanced or managed diet, there is no research that supports alkaline water as a standalone weight loss remedy.
Drinking water that is too alkaline may have adverse effects.
Researchers who looked into the link between alkaline water, an alkaline diet, and cancer said that an alkaline diet could be harmful, as it encourages people to avoid foods that contain important nutrients.
They concluded that "Promotion of alkaline diet and alkaline water to the public for cancer prevention or treatment is not justified."
The pH of water probably does not make much difference to health.
The World Health Organization (WHO) note that, just as too much acid is corrosive, so is too much alkali.
In 2001, scientists published findings following a study in which rats at different stages of life consumed alkaline water of pH 11.2 or pH 12 for a year.
At the end of the experiment, the rats had lost weight or experienced delayed growth, and female rats had fur that was thin in patches and appeared dull. Some of the rats had discoloration in the oral mucosa.
The review that was published in the BMJ found that, among the studies of alkaline water they reviewed, "none [...] supported the promotions that suggest alkaline water supports good health."
How to make alkaline drinking water
Machines called ionizers make water alkaline, but they are expensive.
Bottled mineral water tends to be neutral or slightly alkaline. Some manufacturers may state the pH level of their bottled waters.
Sparkling waters are acidic. Carbonation introduces carbon dioxide, which lowers the pH and increases acidity.
The website alkalinewatersionizers.org promotes water ionizers. It says that "Because ionized water contains so many active hydrogen molecules, it is able to act as a powerful antioxidant that searches out and destroys free radicals."
However, the site also emphasizes the message:
"You must understand that there are no benefits to drinking alkaline water."
It is only the ionizing, they say, that brings the benefits, yet there is little to no published research to support ionized water for health.
The Cleveland Clinic, meanwhile, in their article, "Alkaline water: Don't believe the marketing hype," advise people to drink water, but make it plain water, because too much acidity or too much alkalinity can cause problems.
They point out that the human body is designed to find its own balance.
People should think carefully whether it is worth investing in expensive equipment that is unlikely to make a difference.