Organic anions and potassium salts in nutrition and metabolism

Abstract

The present review examines the importance of dietary organic anions in preventive nutrition. Organic anions are chiefly supplied by plant foods, as partially neutralised K salts such as potassium citrate, potassium malate and, to a lesser extent, oxalate or tartrate salts. Animal products may also supply K anions, essentially as phosphate, but also as lactate as a result of fermentative or maturation processes, but these K salts have little alkalinising significance. Citrate and malate anions are absorbed in the upper digestive tract, while a substantial proportion is probably metabolised in the splanchnic area. Whatever their site of metabolism, these anions finally yield KHCO 3 which is used by the kidneys to neutralise fixed acidity. This acidity essentially reflects the oxidation of excess S amino acids to sulfate ions, which is mainly related to the dietary protein level. Failure to neutralise acidity leads to low-grade metabolic acidosis, with possible long-term deleterious effects on bone Ca status and on protein status. Furthermore, low-grade acidosis is liable to affect other metabolic processes, such as peroxidation of biological structures. These metabolic disturbances could be connected with the relatively high incidence of osteoporosis and muscle-protein wasting problems observed in ageing individuals in Europe and Northern America. Providing a sufficient supply of K organic anions through fruit and vegetable intake should be recommended, fostering the actual motivational campaigns ('five (or ten) per d') already launched to promote the intake of plant foods rich in complex carbohydrates and various micronutrients.

Organic acid bioavailability from banana and sweet potato using an in vitro digestion and Caco-2 cell model

“…The citrate is transported in the mono-protonated form citrate 2- [41]. Oxalic acid from the diet is less absorbed and poorly metabolised in the tissues compared to malate or citrate, and the absorbed part is essentially channelled towards kidney excretion [12]. The high recovery of oxalic acid in the basolateral chamber suggests that metabolism within the cells was minor.…”

“…Previous studies have established the preventive health benefit of organic acid consumption from fruit and vegetables [6][7][8][9][10][11]. Indeed, these are the main sources of organic acids (chelated with potassium or magnesium) such as malate and citrate, which have been shown to exert alkalinizing effects after metabolism, with a potential to prevent low-grade metabolic acidosis inherent to western diet consumption [12][13][14]. These organic anions are absorbed in the digestive tract and metabolised in various tissues, especially the liver and intestine, and finally produce CO 2 and energy [15].…”

“…In plant foods, they are partially neutralised, essentially by potassium. This leads to the production of potassium bicarbonate which neutralises fixed acidity produced from protein catabolism [12]. Besides their alkalinising effect, interest in organic acids is increasing due to their potential to modulate short-chain fatty acid (SCFA) production in the large intestine.…”

“…The objective of the present study is to determine the in vitro release and absorption of organic acids from plant origin, namely citric, malic and to a lesser extent oxalic acids, which are known to play a key role in western dietinduced metabolic acidosis protection [12]. Thus, to further understand organic acid bioavailability from banana and sweet potato as examples of a fruit and a vegetable, an in vitro model combining human gastric and pancreatic digestion followed by human intestinal absorption (via Caco-2 cells) was investigated in this study.…”

Excess Casein in the Diet Is Not the Unique Cause of Low-Grade Metabolic Acidosis: Role of a Deficit in Potassium Citrate in a Rat Model

“…The alkalinizing potential of the diet also depends on the provision of K/organic anions salts by fruits and vegetables [6] , but some other factors could also play a role such as NaCl or Ca and Mg provision [7] . This is illustrated by the ongoing controversy about the role of dairy products and more generally of animal proteins on Ca metabolism, probably refl ecting the complexity of the products [8] .…”