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The acid-base balance by Guillaume Klein

Sports activity has many positive effects on optimizing physical and mental health.


However, regular and prolonged effort, especially in the case of endurance sports, can promote the acid-base imbalance of the body, by creating acid loads leading to harmful repercussions on our body.


1) Understanding the acid-base balance

Our body operates within a narrow blood pH range between 7,36 and 7,42, beyond this limit our health is threatened.

The body has regulatory mechanisms to balance the pH within this limit, allowing the elimination of different acids by the lungs, kidneys, and intracellular and extracellular buffer systems.

However, these mechanisms may turn out to be insufficient because of an excess of acidity, which can no longer properly play their regulatory roles.

The factors of imbalance:

  • An unbalanced diet.
  • Physical inactivity.
  • Excessive physical activity.
  • Stress and intellectual hyperactivity.
  • Pollution.

2) The consequences of an excess of acid loads

To fight against acidosis, the body must make a great effort to balance the blood pH in order to neutralize excess acidity.

It will then draw on the alkaline reserves of the bones, to use the calcium, magnesium and potassium salts, which will be eliminated through the urine.

This phenomenon can lead to demineralization with in particular a loss of bone stock.

Other consequences:

  • Tendon and joint disorders.
  • Muscle fatigue.
  • Increased risk of kidney stones.
  • Weakening of the nervous system.

In athletes, the acidification of the body is a phenomenon to be regulated, because it could cause a weakening of the skeleton and fatigue fractures, but also promote tendinopathies, loss of muscle mass, and an increased risk of infection.

3) Control acidity through food

Foods ingested daily during our meals have direct consequences on the acidity of our body, and will play the role of mediator to restore balance.

The context of modern food:

Today we have access to a substantial offer in terms of food, but which often comes at the expense of quality.

This abundance leads to an excessive consumption of animal proteins, dairy products, refined cereals, processed products, refined sugars and salts, sodas… which will produce a deleterious effect by acidifying the body.

Plants at the heart of balance:

Fruits and vegetables are the main dietary lever for regulating acidity, because they contain organic anions (citrates and malates) which will neutralize acidifying charges.

The concentrations are generally higher in fruits than in vegetables, in particular in citrus fruits and kiwis, with a higher average content of citrates and malates.

Vegetables are richer in potassium than fruits, but have a more balanced ratio of potassium and organic anions (citrates and malates).

  • Citrate is found mainly in citrus fruits and kiwis, but also in potatoes and tomatoes.
  • Malate predominates in apples, cherries, plums, eggplants, cucumbers.
  • The banana is an exception, because unlike other fruits it has a balanced ratio between potassium and organic anions.

Overall all fruits and vegetables are of interest and must be consumed in a varied and balanced way to have an optimal ratio of organic anions (citrates and malates) and potassium.

It is not because certain fruits and vegetables have an acidic flavor that they are acidifying, taking the example of lemon, it is acidic to the taste in particular thanks to the presence of citrates, but alkalizing for the organism.

On the other hand, for some people in the event of metabolic weakness, it is preferable to limit the intake of acidic fruits and vegetables (citrus fruits, kiwis, red fruits, tomatoes, rhubarb…) which will be poorly oxidized and consequently acidify the body.

The PRAL index as an indicator of acidity:

This tool measures the potential renal acid load generated in the body per 100g of food.

The acidifying or alkalizing character of a food depends on its nutritional composition and mainly on its mineral composition and its protein content.

Acidifying foods have a positive PRAL index, conversely alkalizing foods have a negative PRAL index.


  • Acidifying foods are animal products (meat, fish, eggs, dairy products), cereals and legumes.
  • The alkalizing foods are vegetables, fruits, spices.

Some examples :

  • Acidifying foods:
    • Parmesan: PRAL for 100g +34
    • Emmental: PRAL for 100g +21
    • Turkey meat: PRAL per 100g +10
    • Beef: PRAL per 100g +8
    • Egg: PRAL for 100g +8
    • Cod: PRAL for 100g +7
    • Spaghetti: PRAL for 100g +7
    • White rice: PRAL for 100g +5
    • Bread baguette: PRAL for 100g +4
    • Lentils: PRAL for 100g +3
  • Alkalizing foods:
    • Raisin: PRAL for 100g -21
    • Spinach: PRAL for 100g -14
    • Banana: PRAL per 100g -6
    • Celery: PRAL for 100g -5
    • Carrot: PRAL for 100g -5
    • Sweet potato: PRAL per 100g -4
    • Tomato: PRAL per 100g -3
    • Orange: PRAL for 100g -3
    • Apple: PRAL for 100g -2
    • Cucumber: PRAL per 100g -1

A food with a positive PRAL index (acidifying) should not be withdrawn from its diet, but integrated into a suitable meal allowing to respect the balance of the acid-base balance.

Although the PRAL index is interesting for a generalist view, it also has its limits, it will lack precision in terms of the calculation method, and above all it cannot take into account the individual metabolic capacity in the regulation of acids.

4) The case of the athlete

Food is a fundamental point to maintain the acid-base balance of the body, it is all the more important to pay particular attention to it around physical effort and especially in the recovery phase.


After a sporting activity, the body will set up a metabolic window which will extend from 30min to 4h after stopping the effort.

Goals :

  • Cover the losses related to the effort from an energetic point of view.
  • Optimize the body's capacity for reconstruction to promote recovery.

During this window, the body is therefore in full capacity to receive all that you are going to give it in terms of food and hydration.

The athlete must therefore have a suitable food bolus, in order to restore energy and mineral reserves in a healthy way, while avoiding the creation of acid loads.

For an alkalizing plate:

The basis is to incorporate fresh fruits and vegetables in large quantities.

Avoid excess of:

  • Animal protein.
  • Dairy products.
  • Cereals (rice, pasta, bread, etc.).

Fill up on carbohydrates and energy with alkalizing sources: 

  • Fruits frais
  • Dried fruits (apricots, figs, prunes, etc.)
  • Tubers, squash and root vegetables (sweet potato, potato, Jerusalem artichoke, parsnip, butternut, carrot, beet, ...)


  • Green salad
  • Grated raw beet.
  • Varied seasonal vegetables (cabbage, green beans, chard, broccoli, spinach, fennel…).
  • 2 eggs (preferably soft or fried).
  • 200g of sweet potato.
  • 1 plant-based yogurt without added sugars (soy, almond, coconut, etc.).
  • 1 banana.

Seasonings of the meal:

  • Vinaigrette: 1 to 2 tablespoons of a mixture of 50% extra virgin olive oil + 50% extra virgin omega 3 oil (rapeseed, flax, walnuts, camelina ...) + fresh lemon juice and / or (cider vinegar , balsamic vinegar, tamari…) + 1 pinch of unrefined salt.
  • 1 to 2 teaspoons of seeds (squash, sunflower, chia, sesame, flax, hemp, poppy…).
  • Aromatic herbs (parsley, coriander, chives, thyme…).
  • Various spices (turmeric, ginger, black pepper, fennel, cumin, fenugreek, cinnamon…).


The acid-base balance is an important point to respect on a daily basis, and particularly for the athlete in order to activate the recovery factors as well as possible.

Having a balanced diet rich in fresh fruits and vegetables is the guarantee to regulate the acidity of your organism as well as possible for a preservation of the health capital in the long term.


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This content was published by our Ambassador Guillaume Klein (Personal Coach Expert in sports nutrition and health / Ultra endurance specialist)

  • Nutriformation graduate specializing in micronutrition and nutritherapy
  • Trained in sports nutrition by the Evonutri Positive Nutrition Academy
  • Ultra Trail coach trained by the Auvergne Rhône-Alpes Athletics League
  • Dietitian nutritionist FC Metz professional group (since 2018)
  • Dietitian nutritionist FC Metz training center (since 2019)
  • Creator of the EPIC® method

Passionate about sport, and ultra endurance athlete in running and ultra cycling, Guillaume was able to test on himself the benefits of a natural nutritional balance, appropriate to his real needs, and of a specific adapted training. Guillaume appreciates quality products which respect the nutritional needs of the athlete, but also from a health point of view, a composition as natural as possible.

You too can take advantage of his advice and find all our products on this site

If you would like more information or advice, do not hesitate to contact guillaume via his site uses cookies to provide the best user experience. Please accept cookies to continue exploring our site
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