What is acid-base balance, and why is it essential?
Acid-base balance refers to the constant regulation of blood pH within a very narrow range of 7.35 to 7.45—a variation of ±0.1 pH disrupts enzymes and cellular functions. This balance is distinct from stomach acidity or heartburn—see our page on stomach discomfort for digestive disorders of the stomach. Our line of digestive supplements supports overall mineral balance.
- Blood chemical buffers: bicarbonate/CO₂ system (primary plasma buffer), hemoglobin (intracellular buffer), plasma proteins—immediate response (seconds)
- Respiratory regulation: increase or decrease in respiratory rate → adjustment of CO₂ → altered blood pH—response within minutes
- Renal regulation: excretion of H+ ions or retention of bicarbonates depending on pH — response over hours to days — long-term regulatory mechanism
- Urinary pH: ranges from 4.5 to 8.5 depending on dietary intake and regulatory needs—an approximate indicator of acid-base balance but not representative of blood pH (which remains stable)
- Difference between blood pH and urinary pH: blood pH does not “become more acidic” due to diet (the kidneys compensate)—the concept of “body acidification” through diet reflects the acid load excreted in the urine, not a change in the blood
Medical acid-base imbalances: acidosis and alkalosis
- Metabolic acidosis (pH < 7.35): accumulation of nonvolatile acids—renal failure, diabetic ketoacidosis, salicylate poisoning—symptoms: Kussmaul breathing (compensatory hyperventilation), muscle weakness — emergency workup
- Metabolic alkalosis (pH > 7.45): loss of acids or excess of bases — repeated vomiting (loss of HCl), thiazide diuretics — see our acidosis page for differential diagnoses
- Respiratory acidosis: hypoventilation → accumulated CO₂ → acidosis — COPD, severe pneumonia, central hypoventilation
- Respiratory alkalosis: hyperventilation → exhaled CO₂ → alkalosis — anxiety, pain, high altitude
- Diagnosis: Arterial blood gases (pH + PaCO₂ + bicarbonate) + blood ionogram — urgent evaluation if pH < 7,20 ou > s 7.60
Diet and acid-base balance: realities and limitations of the concept
- Foods with renal acid-forming potential (PRAL): meats, fish, cheeses, grains — generate acids that the kidneys must excrete — increase urinary acid load
- Alkalinizing PRAL foods: fruits, vegetables, legumes — provide potassium, magnesium, and citrates — reduce urinary acid load and protect bones (reduced mobilization of bone calcium)
- Magnesium: a major alkalizing mineral — a cofactor for intracellular buffers — deficiency = neuromuscular hyperexcitability + increased tissue acid load — 300–400 mg/day
- Potassium (fruits, vegetables): potassium bicarbonate is a precursor to renal alkalization—a potassium-deficient diet = more acidic urine = risk of uric acid stones and bone demineralization
- Lemon water or sodium bicarbonate: temporarily increase urinary buffering capacity—use judiciously—sodium bicarbonate is useful in treating uric acid stones (therapeutic urinary alkalization)
Bone Health, Fatigue, and Nutritional Strategies
- Bone health and acid-base balance: chronic, uncompensated acid load depletes bone buffers (calcium + phosphate) → progressive demineralization → long-term osteoporosis — see our vitamin D3 line (essential for remineralization)
- Fatigue and Tissue Acidosis: A high acid load impairs cellular enzymatic functions and reduces ATP production → chronic fatigue — an alkalizing diet improves fatigue parameters in several studies
- Nutritional strategy: a ratio of 70–80% alkalizing foods (vegetables, fruits) to 20–30% acidifying foods — gradually increase green vegetables, reduce excess animal protein and processed foods
- Physical exercise: stimulates ventilation (CO₂ exhalation) and kidney function — improves buffer balance — important in preventing latent acidosis
- Seek medical advice if: persistent fatigue + recurrent muscle cramps + recurrent kidney stones — kidney function tests + electrolyte panel to rule out a medical cause
