Bicarbonate is a major element in our body. Secreted by the stomach, it is necessary for digestion. When ingested, for example, with mineral water, it helps buffer lactic acid generated during exercise and also reduces the acidity of dietary components. Finally, it has a prevention effect on dental cavities.
Bicarbonate is present in all body fluids (see table) and organs and plays a major role in the acid-base balances in the human body. The first organ where food, beverages and water stay in our body is the stomach. The mucus membrane of the human stomach has 30 million glands which produce gastric juice containing not only acids, but also bicarbonate. The flow of bicarbonate in the stomach amounts from 400 µmol per hour (24.4 mg/h) for a basal output to 1,200 µmol per hour (73.2 mg/h) for a maximal output. Thus at least half a gram of bicarbonate is secreted daily in our stomach. This rate of gastric bicarbonate secretion is 2-10% of the maximum rate of acid secretion. In the stomach, bicarbonate participates in a mucus-bicarbonate barrier regarded as the first line of the protective and repair mechanisms. On neutralization by acid, carbon dioxide is produced from bicarbonate. A study has underlined that a dose of 6.17 g of sodium bicarbonate rapidly leaves the stomach with the liquid phase of the meal.
Effects of ingested bicarbonate
For digestion, bicarbonate is naturally produced by the gastric membrane in the stomach. This production will be low in alkaline conditions and will rise in response to acidity. In healthy individuals this adaptive mechanism will control the pH perfectly. To modify this pH with exogenous doses of bicarbonate, some clinical experiments have been conducted with sodium bicarbonate loads as high as 6 g. Only a transient effect on pH has been obtained. It is quite possible that bicarbonate in water may play a buffering role in the case of people sensitive to gastric acidity. Thus bicarbonate may be helpful for digestion.
The most important effect of bicarbonate ingestion is the change in acid-base balance as well as blood pH and bicarbonate concentration in biological fluids. It has been studied particularly in physically active people. Among the types of acid produced, lactic acid generated during exercise is buffered by bicarbonate. In a study on sports, a dose of 0.3 g per kg of body weight of sodium bicarbonate was given (15.25 g bicarbonate for a man of 70 kg) to subjects before performing 30 minutes cycling. While blood pH was increased and then maintained constant with this bicarbonate load due to the changes in blood bicarbonate concentrations, increased acidity and decreased bicarbonate blood concentration were observed in controlled subjects. Mineral water which contains bicarbonate (>600 mg/l) may have an effect on acid-base balance. It is the case of Qu zac. The daily consumption of 1.5 liter of Qu zac in healthy subjects has produced a significant increase in the urinary pH due to the ingested bicarbonate (1685 mg/l).
Prevention of renal stones
Bicarbonate also reduces the acidity of dietary components such as proteins. As an example, adding sodium or even more potassium bicarbonate to subjects on a high protein diet known to acidify urine and leading to hypercalciuria (high level of calcium in urine) has been shown to greatly reduce calcium urinary excretion. The effect has been observed with 5.5 g of bicarbonate supplement received daily for two weeks. A recent study presented in the review of literature highlights that a bicarbonate-rich mineral water could be useful in the prevention of the recurrence of calcium oxalate and uric acid renal stones.
Many oral hydration solutions contain bicarbonate showing the usefulness of bicarbonate to control water absorption in patients at risk of dehydration.
Sodium intake is restricted in patients with hypertension, but it is demonstrated that the accompanying anion, such as bicarbonate or chloride, plays an important role. It is now well established that sodium bicarbonate as well as citrate and phosphate salts do not raise blood pressure to the same extent as do the corresponding amounts of sodium chloride. A study on mineral water containing sodium bicarbonate has confirmed the absence of effect on blood pressure in elderly individuals.
Bicarbonate has been shown to decrease dental plaque acidity induced by sucrose and its buffering capacity is important to prevent dental cavities. Other studies have shown that bicarbonate inhibits plaque formation on teeth and, in addition, increases calcium uptake by dental enamel. This effect of bicarbonate on teeth is so well recognized that sodium bicarbonate-containing tooth powder was patented in the USA in October 1985. Sodium bicarbonate has been suggested to increase the pH in the oral cavity, potentially neutralizing the harmful effects of bacterial metabolic acids. Sodium bicarbonate is increasingly used in dentifrice and its presence appears to be less abrasive to enamel and dentine than other commercial toothpaste.