To ensure efficiency of normal physiological and metabolic functions, the hydrogen ion concentration of body fluids is maintained within a narrow range. The extracellular pH is normally in the range of 7.35 to 7.45. The lungs and kidneys are the major organ systems involved in acid-base regulation. Lungs regulate the respiratory component of acid-base balance by varying CO2 elimination, whereas the kidneys are responsible for eliminating the daily non-volatile acid load primarily as ammonium and titratable acid. These organs systems work in concert to maintain acid-base balance. For example, kidney acid excretion is increased in patients with chronic respiratory acidosis. The enhanced elimination of protons permits generation of new bicarbonate to mitigate the decline in systemic pH. In patients with chronic kidney disease (CKD) or renal tubular acidosis (RTA), impaired proton elimination leads to a reduction in the serum bicarbonate concentration. The lungs compensate by increasing minute ventilation to reduce pCO2 and mitigate the decline in systemic pH. In patients with CKD, metabolic acidosis has been linked with loss of bone mineral, skeletal muscle catabolism, increased risk of CKD progression, and death. Patients with RTA are at risk for loss of bone mineral, nephrolithiasis, and kidney function decline, and children with this condition suffer from poor growth. Patients with chronic respiratory acidosis owing to chronic obstructive pulmonary disease are also at increased risk of hospitalization and death.
While the above acid-base abnormalities are well-documented, what is less appreciated is diet-induced low-grade metabolic acidosis. Diet-induced low-grade metabolic acidosis is a clinical condition often unnoticed, but it is a reality. In this condition, the blood pH is at the lower limit of normal range (7.35 – 7.45). If this condition persists for a prolonged period, it can become harmful as it predisposes to metabolic imbalance, leading to systemic complications, such as kidney stone formation, increased bone resorption, reduced bone mineral density, and the loss of muscle mass, as well as the increased risk of chronic diseases such as T2DM, hypertension, and non-alcoholic hepatic steatosis. Acidic conditions in the body are also congenial for the growth of cancers. Acid environment helps tumor cells to produce proteins that make them more aggressive for growth.
Low-grade metabolic acidosis can also become overt metabolic acidosis if a person falls sick or has systemic infection or undergoes a major surgery. In view of the above, depending on whether a person is a vegetarian or non-vegetarian, one has to keep a tab on the acid load in the diet from different sources. Of course, too much consumption of meat adds to acid load in the body, by mainly releasing hydrogen ions or protons during metabolism. Unlike carbohydrates, proteins have disproportionately large excess of hydrogen vs. oxygen atoms. But, regular consumption of sour foods such as citrus fruits or tamarind-containing foods, causes extra burden on saliva to neutralize the acidity in the mouth to protect the enamel of the teeth. To accomplish this the bicarbonate concentration in saliva can vary from 1 to 60 mM. This in turn can drain the blood bicarbonate and bring the blood pH to lower side of the normal range (7.35 to 7.45), if not compensated by the alkaline sources in the food.
Irrespective of dietary choices, blood bicarbonate levels should be maintained at least at 21 mM. In recent years low blood bicarbonate level (< 19 mM) has emerged as an independent risk factor for death, irrespective of other conditions. To maintain blood bicarbonate levels one can add baking soda to foods during cooking or take sodium bicarbonate tablets. It has been proven that a daily dose of sodium bicarbonate slows down the progression of chronic kidney disease. However, the dose should be kept low and it is better to consult a doctor before starting a course of sodium bicarbonate tablets. These can potentially neutralize the acid in the stomach and cause loss of appetite.