Body Fluid pH Balance in Metabolic Health and Possible Benefits of Dietary Alkaline Foods

Abstract

Living cells have several mechanisms to avoid acidic conditions created by excess protons. The protons are extruded to the extracellular space via the plasma membrane by various types of transporters such as the Na + /H + exchanger and monocarboxylate transporters, which hereby contribute to the exclusion of protons in the cells of metabolic tissues including the liver, skeletal muscle, and adipose tissue. Disturbances in the functioning of the transporters cause abnormal intracellular fluid pH of the cells and dysfunction of metabolic homeostasis, leading to the development of metabolic diseases and a decrease in physical fitness level. In addition to the intracellular fluid pH regulation, growing evidence shows that the fluid pH in the interstitial space around metabolic tissues is easily reduced due to weaker pH buffering capacity than that in the cytosol and blood circulation. Therefore, pH reduction in the interstitial fluid may cause the onset of metabolic dysfunction. In contrast, several dietary foods have direct and indirect benefits in maintaining the interstitial fluid pH to the normal range by improving buffering capacities, suppressing proton production, and activating proton transporters, which strengthen the effect of appropriate diet on metabolic health.

Epidemiologic Evidence for Association between a High Dietary Acid Load and the Breast Cancer Risk

“…Besides, there is growing evidence showing that the fluid pH in the interstitial space around metabolic tissues is easily reduced due to weaker pH buffering capacity than that in the cytosol and blood circulation. Whereas the arterial blood pH is strictly regulated due to strong pH buffers such as albumin and hemoglobin, interstitial fluids have only relatively weak pH buffers, bicarbonate, and phosphate, enabling a pH range of 6.60-7.60 [38]. Such interstitial pH reduction might initiate a metabolic dysfunction [39].…”

“…Such interstitial pH reduction might initiate a metabolic dysfunction [39]. In contrast, several nutrients bring benefits in maintaining the interstitial fluid pH within the normal range by improving buffering capacities, suppressing proton production, and activating proton transporters, strengthening the effect of appropriate diet on metabolic health [38].…”

Food intake targeting and improving acidity in diabetes and cancer

“…Under the normal condition, the pH of arterial blood and interstitial fluid is not changed mainly via excretion of the produced protons into urine and partly via the lung as CO 2 (Figure 1). Even if protons are transported into blood vessels, the pH of arterial blood is strictly controlled within the range of 7.35–7.45 by strong pH buffering factors such as hemoglobin (Hb) and albumin (Figure 2) (Aoi, Zou, Xiao, & Marunaka, 2020; Marunaka, 2018). In contrast, the interstitial fluid has only relatively weak pH buffers such bicarbonate and phosphate (Figure 2), therefore the interstitial fluid pH is variable depending on the metabolic condition (i.e., the amounts of produced protons) (Figure 2).…”

“…The word of “alkalizing foods” is very popularly disseminated; however, the alkalizing mechanism is not so well understood. Representative “alkalizing foods” are weak organic acids containing carboxyl groups (the lower part of Figure 3B) (Aoi et al., 2020; Marunaka, 2018). Weak organic acids containing carboxyl groups are really acids at the oral intake (the lower part of Figure 3B), however only the carboxyl group but not the proton (H + ) is absorbed via the intestine and the colon (the lower part of Figure 3B).…”

“…The improvement of acidity of the interstitial fluid (elevation of pH) increases insulin sensitivity (improvement of insulin resistance) (Aoi et al., 2013; Hosogi et al., 2018). Thus, the intake of alkalizing foods would elevate the lowed interstitial fluid pH in diabetes and cancer, resulting in improvement of insulin resistance and prevention of cancer cell growth and metastasis (Aoi et al., 2020; Marunaka, 2018).…”