Proteins

Let's analyze why the idea that proteins always "acidify the body" is an oversimplification and incorrect.

How proteins affect acid-base balance

Proteins are made up of amino acids — organic compounds, each with a unique structure and chemical properties.

From the perspective of their influence on the body's acid-base balance, amino acids are conditionally divided into three groups:

Acidifying amino acids. These are primarily sulfur- and phosphorus-containing amino acids, for example:

• Methionine, cysteine — during metabolism, they release sulfuric acid.
• Phosphoproteins — during breakdown, they release phosphoric acid.

These acids enter the bloodstream and temporarily shift the plasma pH towards the acidic side until the buffering systems (mainly bicarbonate) and kidneys neutralize and excrete them.

Alkalizing amino acids. Some amino acids contain side chains with nitrogenous and alkaline groups, for example: glutamine, arginine, lysine, alanine.

These compounds consume protons (H⁺) during metabolism or release ammonia, which binds with protons to form neutral or weakly alkaline compounds (such as urea or glutamate).

Thus, they contribute to alkalizing the internal environment of the body.

Neutral amino acids. Some amino acids have little direct effect on the acid-base balance but can participate in the synthesis of metabolites that indirectly influence the buffering systems.

Why complete protein is balanced nutrition

"Complete protein" provides the body with both acidifying and alkalizing amino acids, ultimately forming a natural metabolic balance.

How the body maintains blood pH

The body strictly regulates the plasma blood pH within the range of 7.35–7.45. The overall acid-base balance is controlled by:

• Blood buffering systems (bicarbonate buffer, protein buffer, phosphate)
• The kidneys, which excrete excess acids or bases
• The lungs, which regulate CO₂ levels (affecting carbonic acid levels)

Thus, no food can radically "acidify" the body if the organs are functioning normally.

Conclusion

The idea that "all proteins acidify the body" is a myth based on a superficial understanding of metabolism. In reality:

• Only a portion of amino acids have an acidifying effect.
• Alkalizing amino acids balance this influence.
• Complete proteins support homeostasis rather than disrupt it.

Therefore, with adequate, balanced protein nutrition, the body maintains a healthy acid-base balance naturally.

The Myth of Protein and "Acidic Urine"

Proteins do indeed produce acidic residues (mainly sulfuric and phosphoric acids) during metabolism, but this is a natural load to which the kidneys are adapted. With sufficient alkaline minerals (potassium, magnesium, sodium) and in the absence of insulin resistance, urine remains at a normal pH.

Moreover, a protein-rich diet usually increases fat intake, which does not activate aldosterone and does not cause sodium loss.

However, an excess of carbohydrates systematically acidifies urine:

Carbohydrates, insulin, and sodium. High carbohydrate intake stimulates insulin release. Insulin affects the kidneys: it reduces sodium excretion, promoting its reabsorption in the nephron tubules.

However, with prolonged and chronically high levels of insulin (for example, in insulin resistance), the kidneys' sensitivity to sodium is impaired. In this case, despite increased insulin, sodium is retained poorly, and the body begins to lose it in urine.

Sodium loss and activation of the renin-angiotensin-aldosterone system (RAAS). When the body loses sodium, it is perceived as a threat of dehydration and hypovolemia. In response, the RAAS is activated, and the adrenal glands release aldosterone—a hormone that stimulates the kidneys to enhance sodium reabsorption and excrete potassium and hydrogen ions (H⁺).

Aldosterone and urine acidification. Aldosterone activates proton pumps in the distal tubules of the kidneys, increasing the secretion of H⁺ ions into the urine. This makes the urine more acidic. Thus, increased aldosterone → increased H⁺ excretion → urine acidification. At the same time, there is a loss of potassium and a shift in the acid-base balance towards acidosis.

Additional contribution of glucose. At high levels of glucose in the blood and/or urine (glucosuria, characteristic of prediabetes or diabetes), glucose pulls along water and electrolytes (osmotic diuresis), which also leads to additional sodium loss, enhancing aldosterone activity.

Additionally, a high-carbohydrate diet reduces the level of citrates in the urine—these are the main natural buffers that protect against acidification. A low level of citrate is associated with the risk of stone formation and metabolic acidosis.

Conclusion

It is not protein per se that acidifies urine, but an excess of carbohydrates through hormonal and electrolyte mechanisms.

Protein foods can only slightly shift pH if consumed in the context of a mineral- and water-deficient diet. In contrast, carbohydrates—especially refined ones—systematically and deeply acidify urine, causing a cascade of reactions through insulin, aldosterone, sodium loss, and electrolyte disturbances.

This is indeed an important physiological observation that debunks the common myth about the harm of protein due to ammonia formation.

When a person limits protein intake, believing that this will reduce the burden on the liver and kidneys (due to ammonia as a byproduct), they overlook the main fact: the body still needs protein. Proteins — are the building blocks for enzymes, hormones, immune cells, muscles, and organs. In the case of protein deficiency, the body begins to break down its own proteins — primarily from muscles, and in severe cases, from internal organs.

What is ammonia and where does it come from

When amino acids (the main components of protein) are broken down, an amino group (–NH₂) is formed, which is converted into ammonia (NH₃) in the body. This toxic compound is quickly neutralized in the liver, where it is converted into urea and excreted through the kidneys with urine — this is the normal and safe pathway.

What happens on a low-protein diet

Against the backdrop of protein deficiency:

• Catabolism of muscle tissue is activated — muscle protein is broken down to meet the minimum needs of the body.
• At the same time, ammonia is produced directly in the tissues, where there are no specialized enzymes or cells to quickly neutralize it. It accumulates locally, which can cause cytotoxicity, disrupt cell function, and lead to inflammation.
• Subsequently, amino acids and protein remnants enter the bloodstream and reach the liver, where the second stage occurs — ammonia formation in the intestines (especially in the large intestine) under the influence of putrefactive bacteria.
• In the intestines, some ammonia is reabsorbed into the bloodstream, creating additional stress on the liver, which is already working in a compensatory mode.

Why more ammonia is produced, not less

In practice, it turns out that on a full diet, ammonia is produced once — during food digestion, and is immediately utilized. And on a protein deficiency:

• First — in the tissues (where it is harmful),
• Then — in the intestines (where some of it will still enter the bloodstream).

Thus, more ammonia is produced even than with normal protein consumption, and it circulates longer, causing more toxic stress to the body.

Conclusion

The fear of ammonia with protein consumption — has no physiological basis if there are no serious liver function disorders. On the contrary, protein deficiency increases ammonia load and makes it less controllable.

The acid-base balance of the body is determined not by the source of protein (plant or animal), but by the amino acid composition and how these amino acids are metabolized in the body.

How proteins affect the acid-base balance

Proteins are made up of amino acids, each of which can produce either acidic or alkaline products during metabolism.

Amino acids that acidify the body. Some amino acids produce strong acids, such as sulfuric, phosphoric, and hydrochloric acid, when broken down. Examples:

• Methionine, cysteine (contain sulfur) → produce sulfuric acid (H₂SO₄)
• Phosphorus-containing amino acids (e.g., phosphoserine) → produce phosphoric acid (H₃PO₄)

These products acidify the internal environment of the body (in particular, they increase the acidity of urine), as the body has to neutralize or excrete these acids through the kidneys, lungs, and blood buffer systems.

Amino acids that alkalize the body. Other amino acids produce alkaline ionic forms (e.g., bicarbonate, ammonia) as a result of metabolism:

• Glutamine, asparagine, histidine, etc. → provide ammonia groups (NH₃), which can be used to form ammonium (NH₄⁺), and also stimulate the production of bicarbonate (HCO₃⁻), which alkalizes the blood.

Why it doesn't matter whether the protein is plant or animal

Each protein — whether plant or animal — is a mixture of amino acids. It is impossible to say that all protein from plant sources alkalizes, while that from animal sources acidifies. It all depends on the balance of amino acids in a specific product:

• Animal proteins (meat, fish, eggs) contain all essential amino acids and often more sulfur-containing ones, which can lead to a greater acidic response.
• Plant proteins (legumes, nuts, grains) also contain acidic amino acids — especially in grains. For example, wheat produces a significant amount of acidic residues during metabolism.

Thus, both can either acidify or alkalize — it all depends on the specific amino acid profile and combination of products.

The role of complete protein

Complete protein — is a protein that contains all essential amino acids in the necessary proportions. Such proteins are better absorbed, put less strain on the kidneys and liver, and allow the body to:

• Effectively use amino acids for the synthesis of tissues, enzymes, and hormones (rather than for energy purposes)
• Reduce the formation of excess acids or toxins, as there are no excess amino acids to be broken down

Thus, high-quality protein (e.g., egg, collagen, whey protein, a blend of plant proteins with a complete amino acid profile) better maintains the acid-base balance because it does not overload with individual acidic metabolic products.

The proton pump — is a protein on the surface of parietal cells in the stomach that "pumps" hydrogen ions (H⁺) into the lumen of the stomach in exchange for potassium ions (K⁺). This is the main mechanism of acid production — that is, it is thanks to it that gastric juice becomes acidic (pH can be 1–2).

How is this related to blood alkalinity?

During active acid secretion in the stomach, equivalent amounts of bicarbonates (HCO₃⁻) are simultaneously released into the blood — this is called "alkaline tide". That is:

The more acid is produced in the stomach, the more alkali enters the blood.

This is physiologically conditioned:

When H⁺ is formed in parietal cells from water and CO₂ (with the help of the enzyme carbonic anhydrase), HCO₃⁻ is also formed simultaneously. H⁺ ions are released into the stomach, while bicarbonates are released into the blood. Thus:

• The stomach — becomes acidic (high acidity);
• The blood — becomes alkaline (temporarily).

What does this give to the body?

1. Alkalinization of the blood during the active digestive phase helps to compensate for the acidity that can potentially occur due to metabolic products.
2. The bicarbonate system — is one of the main buffers in the blood, and the additional influx of HCO₃⁻ strengthens its ability to maintain a pH around 7.35–7.45.
3. This is also an important component of detoxification and overall homeostasis: with sufficient alkalinity, the blood better binds and removes metabolites, especially acidic ones.

Protein food — the main stimulator of gastric juice secretion

When proteins or amino acids enter the stomach, a powerful chain of stimuli is triggered to activate the proton pump. This is related to several mechanisms:

Amino acids → Gastrin. Proteins, especially aromatic amino acids (phenylalanine, tyrosine, tryptophan), stimulate the production of gastrin — a hormone of the stomach. Gastrin activates parietal cells, stimulating the proton pump: H⁺/K⁺-ATPase begins to actively release hydrogen ions into the lumen of the stomach. As a result — gastric acid sharply increases.

Neural (vagal) stimulation. At the sight, smell, and especially chewing of protein food, the vagus nerve (n. vagus) is activated. It enhances the release of acetylcholine, which directly stimulates parietal cells. Protein food enhances this effect more than carbohydrates or fats.

Proteins require an acidic environment. To break down proteins, an active enzyme pepsin is needed, and it only works in an acidic environment (optimal at pH 1.5–2). The body knows: if there are many proteins, more acid is needed to digest them. This creates a positive feedback loop: the more protein → the more acid → the more actively the proton pump works.