Can Food Acidify or Alkalize Your Body?

Can food acidify or alkalize the body?

“Animal proteins acidify the body, damaging bones and kidneys, which is why one should alkalize.” I've wanted to analyze this hypothesis in detail for years, unfortunately still very widespread despite being debunked by solid scientific evidence.

FOOD ACID-BASE CHEMISTRY
Let's start with the basics: what determines if a food is acidic or alkaline? It depends on what it does with hydrogen ions H⁺: if it releases them, it's acidic; if it accepts them, it's alkaline. Animal proteins and cereal proteins are rich in amino acids that release hydrogen ions, so they are defined as “acidifying.” Fruits and vegetables contain mineral salts that, during digestion, produce bicarbonate capable of accepting hydrogen ions, so they are defined as “alkalizing.”.

pH measures the degree of acidity or alkalinity of a solution. The pH scale ranges from 0 to 14: 7 is neutral, values below 7 are acidic, and values above 7 are alkaline (or basic).

Curiosity: The lemon has a pH of 2.4, making it an acidic food. However, it is actually alkalizing because the citrate it contains is metabolized into bicarbonate and contributes to an alkaline load. In general, the acidifying or alkalizing effect of a food does not depend on its pH, but on the balance between compounds that, after metabolism, produce acids or bases. This is why many fruits and vegetables are alkalizing, even though they may have an acidic taste or pH.

pH and buffer mechanisms
The pH of the blood must always be maintained within a very narrow range: pH 7.35 – 7.45. The body regulates blood pH through three defense systems:
Chemical swabsOur bodies contain molecules that capture hydrogen ions when the blood becomes too acidic and release them when the blood becomes too alkaline. The main buffering molecules are hemoglobin and bicarbonate, which circulate in the blood, and phosphate, found inside cells and in the kidneys.
Pulmonary systemExhaling carbon dioxide helps eliminate hydrogen ions captured by bicarbonate and hemoglobin in the blood.
Renal systemThe kidneys regulate acid-base balance by eliminating or retaining hydrogen and bicarbonate ions as needed by the body.

Urine pH changes based on diet:
pH 5.5–6.5 (acidic): diet rich in animal protein, salt, or phosphorus
pH 6.5–7.5 (alkaline): vegetarian or vegan diet rich in fruits and vegetables
Urine reflect what we eat; they are the waste product through which the kidney expels excess acids or bases in the blood.

ACID-BASE HYPOTHESIS
Proponents of the acid-base hypothesis believe that an excess of animal protein increases the body's acidity, which can damage bones and kidneys (1). According to this hypothesis, normal physiological mechanisms would not be sufficient to compensate for this acidity, and it would therefore be necessary to consume alkalizing foods. Let's critically analyze the arguments supporting the hypothesis, based on the most rigorous scientific evidence. The hypothesis arose from the observation that high consumption of animal protein increases calcium in the urine. Let's start from this point.

Urine calcium comes from bones
Hypothesis: Animal proteins increase the acidity of the body. To neutralize it, the body would use calcium salts present in the bones. This would lead to an increase in calcium in the urine and, in the long term, a loss of bone mass, resulting in an increased risk of osteoporosis.

Analysis: High-protein diets have been shown to correlate with greater bone density and a lower risk of fractures. (2,3,4,5) This would be enough to demonstrate that the hypothesis is disproven, but let's be absolutely sure.

Why does eating

Measuring calcium in urine does not reveal its origin, therefore, further studies using calcium isotopes are necessary to track the fate of dietary calcium. These studies have shown that consuming more protein increases the amount of calcium absorbed in the intestine. Proteins seem to make the intestine more efficient at absorbing calcium already present in the diet (7). Thus, there is more calcium in the urine simply because more is absorbed in the intestine.

Where does the majority of absorbed calcium come from? Some hypotheses have been put forward, but unfortunately, the mechanism is still unknown today. (Yet another example of how many things we still don't know...)

Renal overload
Hypothesis: After a meal rich in animal protein, the kidney increases glomerular filtration rate (GFR), and this strains the kidney in the long term (8).

Analysis: Eating more protein increases GFR, but this is an absolutely normal physiological adaptation (9). We analyzed the false belief “protein strains the kidneys” in detail in this this insight.

Uric acid
Hypothesis: Diets very rich in animal protein lower urine pH to values below 5.5. At this pH, uric acid precipitates and forms crystals (10).

Analysis: A urinary pH below 5.5 favors uric acid precipitation, but does not necessarily cause it. The risk also depends on the concentration of uric acid in the urine, hydration, and the presence of obesity, insulin resistance, or metabolic syndrome. (11, 12) If you have problems with uric acid, I recommend live session with the functional medicine doctor, Dr. Manfra.

Scientific evidence
Let's conclude with the very rigorous systematic review and meta-analysis by Fenton (13), which asked the question: “Do acidifying foods damage bones?” To answer this, Hill's criteria were applied, a tool that helps distinguish between a simple association and a true cause-and-effect relationship. Applying this rigorous methodology, the conclusion is clear: there is no scientific evidence that “acidifying” foods cause bone disease, nor that an “alkalizing” diet protects them. (13)

FINAL QUESTIONS

Does eating animal protein acidify the body?
No, a healthy body is able to maintain blood pH within the 7.35-7.45 range, and no food can alter this balance. No harm to bones and kidneys has been demonstrated; on the contrary, a higher protein intake is associated with
– a reduced risk of developing chronic kidney disease (14)
- greater bone density and lower risk of fractures (2,3,4,5)

Do vegetables or alkaline water make the body alkaline?
No.

Is there evidence for alkaline supplements?
Only if mineral salts are added. The positive effect on bone health has not been proven (15).

Are minerals in fruits and vegetables unavailable because they are chelated by antinutrients?
Phytates (found in whole grains, legumes, and nuts) reduce the absorption of certain minerals, especially iron and zinc, but in a varied diet, the effect does not lead to deficiencies.

If I eat a carnivorous diet, do I need to take supplements to alkalize my body?
No, otherwise the Inuit (who ate practically only animal protein and fat) would have gone extinct.

We hope this in-depth analysis was helpful to you. Leave us a comment; we'd love to know what you think or if you have any questions.

P.S.
If someone is trying to sell you machinery for producing alkaline/hydrogen water, please Read here

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