Health Hazards of Metabolic Acidosis

by Ben Best

The structure and function of proteints, including enzymes, can be compromised by body tissues being too acidic. A study of American adults showed blood plasma acidity increasing 6-7% between the ages of 20 and 80, with most of the change occuring after age 50 [AMERICAN JOURNAL OF PHYSIOLOGY; Frassetto,LA; 271(40):F1114-F1122 (1996) and JOURNAL OF THE AMERICAN GERIATRICS SOCIETY; Berkemeyer,S; 56:1442 (2008)].

The traditional Western diet is high in animal protein (meat,eggs,cheese) as well as bread and white rice, which are acidifying, in contrast to fruits and vegetables, which are alkaline [BIOCHEMIE; Williams,RS; 124:171-177 (2016)]. The acid from protein is produced by liver oxidation of amino acid sulphydryl groups and by hydrolysis of phosphate esters from lipids. Amino acid nitrogen is converted to ammonia and then to urea in the liver. Ammonia from the liver combines with acid hydrogen ion to form ammonium, which the kidney excretes. The kidney creates ammonium from the amino acid glutamate. The kidney excretes ammonium and excretes acid by exchange with alkaline bicarbonate, which is reabsorbed [JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY; Paulev,PE; 56(supp 4):155 (2005)].

[Carbonic Anhydrase ]

Bicarbonate (HCO3) is a buffer molecule which can combine with acid to form carbon dioxide (CO2) during acidosis, or release the acidic hydrogen ions (H+) during alkalosis. In acidosis the kidney reabsorbs bicarbonate and excretes acid, whereas in alkalosis, the kidney excretes bicarbonate and reabsorbs the hydrogen ions. Normally, two-thirds of acid excretion by the kidney is in the form of ammonium, but ammonium excretion will be increased by a ketogenic diet. When blood volume is low, aldosterone release stimulates the sodium-potassium pump in the kidney to excrete more potassium and reabsorb more sodium. Aldosterone has the same effect when blood potassium is high [CLINCIAL JOURNAL OF THE AMERICAN SOCIETY OF NEPHROLOGY; Palmer,BF; 10(6):1050-1060 (2015)]. Excretion of acid (hydrogen ion) can occur by exchange of either potassium or sodium. If sodium is high, more sodium will be excreted in exchange for reabsorption of acid, whereas if potassium is high, more acid will be reabsorbed in exchange for the potassium which is excreted.

Metabolic acidosis increases insulin resistance and the likelihood of type 2 diabetes [JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY; Paulev,PE; 56(supp 4):155 (2005)]. Metabolic acidosis increases inflammation, heart arrhythmias, osteoporosis, calcium kidney stones, and muscle wasting [EPILEPSY & BEHAVIOR; Yuen,AWC; 74:15-21 (2017)]. Metabolic acidosis increases the stress hormone cortisol in females [JOURNAL OF NUTRITION; Remer,T; 138:426s-430s (2008)]. Cancer cells use an acidic environment to resist cell death (apoptosis), to spread (metastasize), to escape the immune system, and to promote new blood vessels that can support the growing tumor [CELLULAR AND MOLECULAR LIFE SCIENCES; Peppicelli,S; 74(15):2761-2771 (2017)].

Seventy percent of people over age 80 are affected by osteoporosis. Osteoporosis is about 3 times as prevalent in women as in men, [ARCHIVES OF OSTEOPOROSIS; Wade,SW; 9:182 (2014)]. especially due to reduced plasma estrogen after menopause [AMERICAN JOURNAL OF CLINICAL NUTRITION; McTiernan,A; 89(6):1864-1876 (2009)].

Bones become demineralized in response to acidosis, which results in osteoporosis and bone fracture. The problem is worsened by excessive dietary table salt (sodium chloride) [JOURNAL OF NUTRITION; Frasseto,LA; 138:419s-422s (2008)]. Calcium and sodium compete for reabsorption in the kidney, but sodium chloride causes more calcium excretion than sodium alone. Sodium chloride increases metabolic acidosis and decreases kidney reabsorption of alkaline bicarbonate by the increase in parathyroid hormone (which is secreted to induce calcium release from bone to compensate for calcium excretion by the kidney) [JOURNAL OF BONE AND MINERAL RESEARCH; Frings-Muethen,P; 23(4):517-524 (2008)]. High salt intake can increase blood prossure and kidney disease [KIDNEY RESEARCH AND CLINICAL PRACTICE; Frame,AA; 36:117-131 (2017)]. Persons whose blood pressure is most increased by salt are the persons whose metabolic acidosis is most increased by salt [HYPERTENSION; Sharma,AM; 16(4):407-413 (1990)]. Most Americans consume more than double the minimum daily intake of sodium recommended by the American Heart Association [MAYO CLINIC PROCEEDINGS; Clegg,DJ; 92(8):1248-1260 (2017)].

Moderate protein (between 10-20% of calories) may maintain bone in post-menopausal women [AMERICAN JOURNAL OF CLINICAL NUTRITION; Hunt,JR; 89(5):1357-1365 (2009)]. Potassium bicarbonate by alkalinization promotes maintenance of muscle and bone in older adults  [JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM; Dawson-Hughes; 94(1):96-102 (2009) and JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM; Ceglia,L; 94(2):645-653 (2009)]. Calcium, Vitamin D, and potassium-rich fruits and vegetables reduce muscle wasting and preserve muscle mass in the elderly  [AMERICAN JOURNAL OF CLINICAL NUTRITION; Dawson-Hughes,B; 87(3):662-665 (2008)].

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