Low-Grade Metabolic Acidosis

Metabolic acidosis is a prevalent but often overlooked chronic condition in the Western world, characterized by the body's retention of acid, leading to a depletion of bicarbonate stores. Although the term 'metabolic acidosis' is commonly associated with low blood pH or acidemia due to a metabolic abnormality, this can be misleading since most cases of metabolic acidosis do not necessarily show acidemia. Acidemia usually only manifests when the condition becomes severe, and the body's buffering capacity can no longer maintain a normal pH level. Notably, the body maintains a normal blood pH of 7.35-7.45 at the expense of its bicarbonate reserves, a key marker for detecting metabolic acidosis. Optimal serum bicarbonate ranges from 25-30 mEq/L. 

The term 'low-grade metabolic acidosis' refers to the state where there are no apparent or noticeable adverse effects, but the body is retaining acid, depleting bicarbonate stores, and causing damage to various tissues. While blood pH and bicarbonate levels might still be within the 'normal' range, any slight decrease can indicate the presence of metabolic acidosis.

It has been observed that with low-grade metabolic acidosis, the body's total blood buffering capacity is reduced, increasing reliance on muscle, bone, and connective tissue for the elimination of additional acid. Chronic metabolic acidosis can worsen kidney function over time and may cause an increased loss of sodium, potassium, water, magnesium, and calcium.

In a healthy body, several buffering systems combat acid accumulation. But, a decrease in buffering capacity, or the inability to meet the acid load, can lead to problems such as muscle, connective tissue, and bone breakdown. The damage caused by mild acidosis includes increased removal of minerals from the bone and increased risk of osteoporosis and kidney stone formation. A common buffering system in the body is bicarbonate, which maintains a normal blood pH. Measuring fasting serum bicarbonate levels is thus critical in checking for low-grade metabolic acidosis. The balance between acid and base in the body is defined by the balance of hydrogen ions and hydrogen ion acceptors, such as bicarbonate and citrate.

Diet is a significant factor in maintaining the body's acid-base balance, with animal protein being the largest source of dietary acid due to its high sulfur-containing amino acids, which form sulfuric acid and hydrogen ions in the body. In contrast, fruits and vegetables are high in organic anions that get converted to bicarbonate, a base that neutralizes the acid. Acid-base status is maintained in the body through various means, including reliance on the kidneys for the elimination of acid. However, certain diets, like animal-based or carnivore diets, can exceed the kidneys' acid elimination threshold, leading to acid retention and negative effects on numerous body systems.

In conclusion, low-grade metabolic acidosis is common in the Western world, and medical professionals should place greater emphasis on its detection and management. By providing ways to test for metabolic acidosis and suggesting strategies to neutralize a high dietary acid load, it is hoped that clinicians can better understand this condition and its treatment.

• Type 2 diabetes.
• Insulin resistance.
• Increased gluconeogenesis.
• Hypertension.
• Bone loss.
• Osteoporosis/osteopenia/sarcopenia
  • Mineral loss from bone matrix.
  • Increased osteoclast activity (more bone breakdown).
  • Reduced osteoblast activity (less bone building).

• Muscle loss and reduce muscle strength.
• Connective tissue loss.
• Fibromyalgia.
• Hyperuriceamia
  • Gout.
• Kidney function decline
  • Tubulointerstitial damage.
• Kidney stones
  • Less citrate to bind to calcium and more calcium to oxalic acid increasing calcium oxalate stone formation.
  • Reduced urine pH increasing uric acid stone formation.
• Salt loss out the urine
  • Negative sodium and chloride balance.
• Other mineral deficiencies
  • Increased loss of sodium, chloride, potassium, calcium, magnesium, sulfate and phosphate out the urine.
  • The sodium and potassium loss are due to a decrease in the reabsorption of these minerals by the kidneys, which likely reduces the reabsorption of taurine
  • The loss of calcium, magnesium and phosphate are from bone losses.⁷
• Taurine loss
  • Increased water loss in the urine.
• Dehydration.
• Decreased exercise performance.

Reference 

DiNicolantonio JJ, O'Keefe J. Low-grade metabolic acidosis as a driver of chronic disease: a 21st century public health crisis. Open Heart. 2021;8(2):e001730. doi:10.1136/openhrt-2021-001730 This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license,