Which pH is the most alkaline

PH value

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The pH value plays an important role for the body. Depending on what functions liquids have in the body, this can vary. Deviations can have health effects.

The pH value is a measure of how acidic or basic a solution is. It indicates how many hydrogen ions (H +) there are in it. The following applies: the lower the pH value, the more acidic the solution. In the medical sense, it is often about the pH of the blood, which is around 7.4 in healthy people.

The pH value can range from 0 (extremely acidic) to 14 (very alkaline). The following generally applies:

  • pH value <7 = acidic
  • pH value = 7 = neutral (e.g. pure water)
  • pH value> 7 = alkaline (basic)

The pH value plays an important role in countless, sometimes vital, metabolic processes in the human body, for example:

  • the sugar metabolism (glycolysis)
  • muscle activity and the spread of excitation in the heart
  • the vascular resistance
  • the oxygen binding of the blood through the red blood pigment (hemoglobin)

The scientific definition of pH is: pH is the negative decadic logarithm of the hydrogen ion concentration, pH = -lg [H+]

The abbreviation "pH" is derived from potentia hydrogenii from which translated means something like "strength of hydrogen".

pH value: blood gas analysis

The pH value (together with other values) can be determined quickly and easily in everyday clinical practice using a blood gas analysis (BGA). It also plays a role in emergency medicine, as the pH of the blood can be an important indicator of certain diseases or disorders.

During a blood gas analysis, the doctor checks whether the pH of the blood plasma is higher or lower than in healthy people:

  • A pH range of 7.36 to 7.44 is considered normal.
  • If the pH in the blood falls below 7.36, acidosis is present.
  • If the pH rises above 7.44, doctors speak of alkalosis.

pH value: acid-base balance

The term acid-base balance is understood to be the body's regulating system, which is supposed to keep the pH value in the blood stable.

To do this, the body uses buffer systems, for example in the blood and urine. These are mainly proteins that can bind excess hydrogen ions or - if the concentration is too low - release hydrogen ions into the blood. These proteins include, for example, hemoglobin and albumin.

The body keeps the pH of the blood at a constant level, primarily through the lungs and kidneys, but also with the help of the liver: On the one hand, it breathes off the acidic carbon dioxide through the lungs, on the other hand, the kidneys contribute to the acid-base Household by them

  • either excrete hydrogen ions when the blood pH is too low (there is too much acid in the body),
  • or by using hydrogen carbonate (bicarbonate, HCO3-), a base, is released into the urine when the blood pH deviates too much.

In acidosis, the body is to a certain extent over-acidic, for example if the pH value in the blood drops due to organic causes - such as in metabolic diseases, kidney diseases or lung diseases.

Video: Acidification through diet - is that really possible?


Table: pH values ​​of various body fluids and organs (examples)
Body fluids, organsnormal pH range
blood7,36–7,44
urine4,5–7,9
(usually slightly acidic, but also alkaline depending on your diet)
stomach1–4
bile6,5–8,2
Pancreatic secretions7,5–8,8
chair7
Small intestine> 8
saliva5,5–7,8
skin5.2-5.8, mean 5.5 ("protective acid mantle");
Exceptions are e.g. B. Armpits (pH 7.1), soles of the feet (pH 7.0) and the skin area around the anus (pH 6.5).
Sweat4,5
(Infection protection through antibacterial effect)
Vagina (sheath), in the lower two-thirds4–5
Cervical secretion (cervical mucus) or upper third of the vagina7–8,5
Vaginal discharge in sexually mature women3,8–4,5

Vaginal discharge before the first menstrual period (menarche) and after the last menstrual period (menopause)> 5
Amniotic fluid7-7,5
sperm7,2–8
Body cells (cell plasma)There are normally more hydrogen ions in body cells than in the blood - here the pH value is around 7.0–7.3.

pH value: disorders of the acid-base balance

Doctors differentiate between so-called pH disturbances

  • respiratory and
  • non-respiratory (metabolic) disorders.

Respiratory disorders

In the case of a respiratory disorder, the pH value changes due to a problem in the area of ​​the lungs or breathing. In such cases, the body tries to rebalance the pH through the kidneys and liver.

low blood pH (acidosis)

Respiratory acidosis (acidosis) can occur, for example:

  • Obstruction of the airways or prevention of gas exchange in the lungs, e.g. B. with pulmonary edema ("water in the lungs")
  • Inflammation of the lungs (pneumonia)
  • Loss of functional lung tissue (e.g. in tuberculosis)
  • insufficient respiratory drive (for example in the case of intoxication with sleeping pills)
  • Paralysis of the respiratory muscles (e.g. in polio)
  • Respiratory reflex malfunction

The body reacts sensitively to a disturbance in its acid-base balance. In the case of acidosis (pH <7.36), the following changes and complaints may occur:

  • The blood sugar levels are increased (hyperglycaemia).
  • Potassium rushes out of the cells and causes its concentration in the blood to rise (hyperkalemia).
  • Excitations in the heart are transmitted more slowly.
  • Cardiac arrhythmias can occur.
  • The heart strength sinks, the vessels widen.
  • There is a threat of a drop in blood pressure.
  • Breathing can be deepened (so-called Kussmaul breathing).
  • The brain pressure can increase.
  • The victim can become unconscious.

pH value in the blood too high (alkalosis)

On the other hand, those who breathe too quickly and too deeply (excessive breathing with hyperventilation), for example due to stress or excitement, excrete too much acid through the lungs. Respiratory alkalosis develops, in which the blood pH increases.

Possible symptoms of alkalosis (pH> 7.44) include:

  • The blood sugar levels are too low (hypoglycaemia).
  • Potassium rushes into the cells and causes the concentration in the blood to drop (hypokalaemia).
  • Cardiac arrhythmias occur.
  • Cramps can occur.
  • Breathing may be decreased and shallow.

If doctors diagnose alkalosis or acidosis, they try to bring the pH back into the correct range. In addition to immediate measures, drugs that work against the cause of the disorder (such as an infection) are suitable for this.

Non-respiratory disorders

In a non-respiratory disorder, the cause is not in the lungs. The body can therefore try to remove acids from the circulation or to hold back more acids by increasing or decreasing breathing.

Non-respiratory hyperacidity can occur, for example, in:

When vomiting violently, on the other hand, the pH value rises (becomes more basic or more alkaline) because the body loses a lot of stomach acid - a non-respiratory alkalosis develops.

Acidification through diet

Colloquially, it is often referred to as hyperacidity from the diet. Acids accumulate in the body, for example, with a very meat-heavy diet, bases are mainly absorbed through plant-based foods.

For otherwise healthy people, however, it is hardly possible to shift the pH value in the blood through poor diet. Thanks to its buffer systems, the body can appropriately absorb the acids and bases that it takes in during nutrition - and thereby keep the pH value constant.

For this reason, concepts such as a so-called acid-base diet are neither comprehensible nor sensible from a scientific point of view.

Reading tip:Carbonated water: acidification from fizzy drinks?

Why a high acid load can still be unfavorable

However, a very one-sided diet that contributes to a high acid load (e.g. due to a high proportion of meat) can still be unfavorable: Because the pH value of the blood remains unchanged, the body still has to get rid of an increased acid load.

This usually happens when the kidneys excrete more acids in the urine. This is measurably more acidic in those affected.

Reading tip:Urine pH

As a result of this acid excretion, the value of the stress hormone cortisol increases. Increased cortisol levels can have long-term health consequences, for example increased blood pressure. Therefore a high acid load can indirectly be detrimental to health.

Herold, G .: Herold Internal Medicine. Self-published, Cologne 2020

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Pay attention to the discharge. Online information from the Deutsche Apothekerzeitung: www.deutsche-apotheker-zeitung.de (as of April 12, 2018)

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Last content check:13.08.2020
Last change: 15.09.2020