Nutrition Myths
Difference between acidic food and acid forming food.


  • Acidic foods and acid-forming foods exert different effects on the body.
  • Acid-forming food may reduce the urine pH, but not the blood pH, and has no impact on health, contrary to the ash-acid hypothesis.
  • Acidic food, is not associated with the urine or blood pH, but with the pH of the food itself. It is linked with worsening the reflux symptoms in people with GERD.


Difference between acidic food and acid-forming food

Acid-forming foods and acidic foods are unrelated, yet often confused. The confusion most commonly occurs when used in reference to “acid-ash hypothesis” which is based on acid-forming foods.

Acid-forming foods

Acid-forming foods contain inorganic minerals, most of which are negatively charged.

They form acid in the body after digestion and absorption by contributing hydrogen ions.

The more hydrogen ions in the liquid, the more acidic the liquid gets.

It can be measured in the lab by calculating the net charge of the inorganic residue after burning organic matter or using pH urine tests or mineral contents of urine.

The concept of acid/base forming foods is the basis of the alkaline diet which claims that the the acid-forming foods are detrimental for health, while base-forming foods are health protective.

Acid-forming food characteristics: (1, 2, 3, 4, 5)

  1. Not related to sour taste.
  2. Contain negatively charged minerals (acid-ash), such as phosphate, chlorine and sulfur.
  3. Ash can be measured either in a lab using the actual food or by urine tests after the food has been digested and absorbed.
  4. They contribute extra hydrogen ions to the body, resulting in a slight drop in blood pH which is quickly regulated by a number of acid-base balancing (buffering) mechanisms in the body, adjusting it back to an optimal pH.
  5. One of the buffering mechanisms is via the kidneys. Kidneys filter extra acids and acid forming minerals that are then excreted through urine. The presence of these minerals lowers urine’s pH.
  6. Acid-forming measurement is used in acid-ash hypothesis which states that acid-forming foods, such as proteins (due to their high acid-ash contents), cause blood pH to drop and bones to release calcium to buffer this acidity. The hypothesis has been shown to have no scientific evidence supporting it.

Acidic foods

Acidic foods have a sour taste and are tested in their natural intrinsic form – before it is ingested, digested and broken down.

Intrinsic food acidity has no relation with the pH of urine and can be tested by using an electronic device called a pH meter in liquefied food.

Acidic food characteristics: (1, 2, 3, 4, 5)

  1. Have a sour taste.
  2. Acidity (pH) is measured by an electronic device called a pH meter applied inside liquefied food. It measures the amount of free hydrogen ions which determine the level of acidity of the liquid. The more hydrogen ions there are, the more acidic the liquid is.
  3. Is not related to acidity changes in the blood or urine.
  4. Acidic foods have a pH < 7. The closer to 0 pH that the food is, the more acidic it is. Most of the foods we eat are acidic (pH is below 7). (read more..)
  5. Acidic foods may worsen the symptoms of acid reflux in people who have been diagnosed with gastroesophageal reflux disease (GERD).
  6. Acidity or alkalinity of the ash is not necessarily related to the acidity or alkalinity of the food.
  7. An example of an acidic food with alkaline effect on the body is lemon.
    Lemon juice has pH = 2.2 which is highly acidic on its own, however after digestion and absorption by the body the remaining inorganic material (ash) contains mainly alkaline minerals. This net alkaline inorganic mineral content has an alkalizing effect on the urine pH.

NOTE: Results of urine pH and blood pH (or body alkaline-acid balance) is frequently confused. Urine pH is different from blood pH and the tests are different and unrelated.

Difference between acid foodic and acid-forming food


You will find a summary of the most common nutrition myths and evidence-based nutrition facts here.

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