Do you also drink magic water every morning to maintain your body’s pH? That is exactly how self-proclaimed health experts now recommend everyone start their day. They promise that the alkaline diet will remove all inflammation from your body and make you the healthiest person in the world. Some even claim it could cure cancer.
Let’s take a closer look at what the alkaline diet involves.
Alkaline eating is a trend that has regained popularity and claims that people should keep their body’s pH balanced through diet. The idea is that excessive acidity in the body causes inflammation, accelerates ageing and creates favourable conditions for cancer cells to develop.
To correct this, you are supposed to eat alkaline foods to keep your body’s pH balanced. One news platform, for example, states that cheese, milk, salt, meat and grains make the blood more acidic. Apple cider vinegar and lemon juice, on the other hand, are said to have an alkaline effect on the body.
What does the body’s pH actually mean?
pH indicates how acidic or alkaline a solution is. The more free hydrogen ions there are, the more acidic the environment and the lower the pH.
The body is not one large container filled with a uniform liquid. It consists of many separate environments, each with its own pH, which the body regulates according to that environment’s function.
The stomach, for example, needs to be highly acidic. The pH of stomach contents can be approximately 1–3. This acidity is needed to digest proteins, activate pepsin and destroy many microorganisms that enter the body with food. It is therefore incorrect to claim that an acidic environment is always harmful to the body.
“Body pH” is not a single, precisely defined measurement. Different parts of the body are supposed to have different pH levels: the stomach is highly acidic, the blood is slightly alkaline, and urine pH can fluctuate considerably.
In medicine, when acid–base balance is discussed, it usually refers primarily to blood pH. Normal blood pH is approximately 7.35–7.45, which means that blood is already naturally slightly alkaline.
The body keeps blood pH within a very narrow range because proteins, enzymes, cell membranes, the nervous system and heart function all depend on an appropriate pH.
What happens when blood pH moves outside this range?
When blood pH moves outside the stated range, the function of almost all proteins, enzymes, ion channels and cells is disrupted. The pH scale is logarithmic, meaning that a change from 7.4 to 7.1 may seem small, but the concentration of hydrogen ions has actually approximately doubled.
Minor deviations may not cause symptoms in themselves. The following signs are primarily associated with severe or rapidly developing acid–base disorders.
If the blood becomes too acidic:
Breathing becomes faster and deeper.
The heart muscle may become weaker.
Blood pressure may fall.
If the blood becomes too alkaline:
The amount of ionised calcium decreases.
Muscle cramps and twitching occur.
Heart rhythm disturbances may occur.
This shows that blood pH is not something you should try to push in a more alkaline direction. It is more like body temperature, which has a narrow normal range and for which deviations in either direction are harmful.
How are foods classified as alkaline?
In the world of alkaline diets, the term most commonly used is PRAL or potential renal acid load. It estimates how much acidic or alkaline residue the kidneys must remove through urine after food has been metabolised. It primarily considers the protein, phosphorus, potassium, magnesium and calcium content of food. However, this system was developed to assess the acid load on the kidneys and urine pH, not the body as a whole.
Using this approach, fruit and vegetables and some legumes are usually classified as “alkaline”. The body can, for example, convert the citrate found in fruit into bicarbonate, meaning that the kidneys need to excrete less acid and the urine may become more alkaline.
Meat, fish, eggs, cheese and grains are often labelled “acidic” because some amino acids in proteins can produce sulfates during metabolism, while phosphorus can produce phosphates, which the kidneys then have to remove.
This means that an alkaline food is not chemically alkaline; it has simply been classified in that category according to its PRAL value.
Scientific research uses PRAL, among other methods, to assess the potential acid load of food, but lists of alkaline and acidic foods found online do not necessarily apply this system consistently.
What does an alkaline diet actually affect?
In a healthy person, a normal diet does not significantly alter blood pH because the lungs, kidneys and buffer systems keep it stable. The acid load from food may become more relevant in conditions such as kidney disease, when the kidneys can no longer remove acids effectively enough.
The most noticeable effect of this type of diet is on urine pH, because the kidneys must remove acidic and alkaline compounds produced during metabolism from the body.
Food can also temporarily affect the pH of the mouth, stomach and intestines, but these changes are usually local and short-lived. A change in the pH of the mouth or stomach does not mean that blood pH has changed at the same time.
What can urine pH affect?
Urine pH affects how well different substances dissolve in urine. This is why urine pH is important in cases such as kidney stones. Acidic urine can promote the formation of uric acid stones, while overly alkaline urine can promote the formation of calcium phosphate stones.
Urine pH therefore has an important physiological effect, but that effect is mainly limited to the kidneys and urinary tract. More alkaline urine does not mean better health and does not indicate the pH of the blood or other tissues.
The alkaline diet and inflammation
An alkaline diet typically includes more fruit and vegetables, legumes and other unprocessed plant foods. At the same time, it recommends reducing added sugar, alcohol, highly processed foods and processed meat. Such a change can indeed improve health and reduce some markers associated with chronic inflammation.
However, this is not because the body has become more alkaline. The benefits may come from a higher intake of fibre, vitamins and plant bioactive compounds, changes in the gut microbiome or weight loss.
No diet can remove all inflammation from the body, either. Inflammation is a normal immune response, and there can be many different reasons why it becomes chronic.
How is the alkaline diet supposed to treat cancer?
The claim that the alkaline diet can treat cancer is based on the observation that the environment around a tumour may be more acidic. This leads to the false conclusion that acidic food created this environment and that alkaline food could neutralise it. In reality, the more acidic environment is caused by the tumour’s own altered metabolism and inadequate blood supply.
Making urine more alkaline does not make the area around a tumour alkaline. Nor can diet raise blood pH to a level that would destroy cancer cells.
Some observational studies have linked a higher dietary acid load to cancer risk, but this does not prove that acidity in the blood or “body” is the cause. There is no clinical evidence that an alkaline diet can treat existing cancer.
A possible exception: chronic kidney disease
In a healthy person, the kidneys can remove the acid produced by a normal diet. In chronic kidney disease, the kidneys’ ability to excrete acids and produce bicarbonate may decline. This can result in metabolic acidosis, which is assessed on the basis of the blood bicarbonate level.
A diet with a lower acid load, which is often plant-based, may help control acidosis in selected patients, but this is not a general “alkaline diet” or a treatment for kidney disease as a whole.
In summary: a healthy diet, but for the wrong reasons
The alkaline diet is best viewed as yet another trend associated with treatment claims that have no scientific basis. There is no scientific evidence that people can use food to make their entire body more alkaline and thereby eliminate inflammation, slow ageing or treat cancer.
The benefits of the diet have a much simpler explanation. If someone starts eating more fruit and vegetables and less added sugar, alcohol and ultra-processed food, their health may indeed improve. This is due to their new, more nutrient-dense diet.
The alkaline diet is a good example of how sensible dietary advice can be paired with a misleading explanation. That is why it is worth assessing not only which foods are recommended, but also how the promised health effects are justified.
How can you distinguish science from marketing?
You should be especially cautious about any dietary advice if the person giving it:
promises that one diet can treat several different diseases
recommends stopping treatment prescribed by a doctor
makes treatment claims without reliable research
sells supplements as the solution
dismisses criticism as pharmaceutical industry propaganda
does not disclose their education or professional qualifications
A healthy person can adjust their diet according to how they feel, their goals or their preferences, but in the case of illness, nutrition therapy should be based on the diagnosis and test results and planned together with an appropriately trained specialist.
When you encounter a new diet trend, ask:
Are the claims supported by high-quality human studies?
Does the person giving the advice stand to gain anything from promoting this “miracle solution”?
Healthy eating does not need a miraculous name or a made-up pseudoscientific explanation to work. The alkaline diet’s recommendation to eat more fresh fruit and vegetables can be beneficial, but not because these foods make the body more alkaline. It therefore makes sense to keep the good food choices on the menu while taking a critical view of the misleading health claims built around them.
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