The acid-base balance of the blood is a significant determinant of bone health. Poor quality diets and those high in protein can increase the acid load of the body because the metabolism of phosphorus and sulphur is able to form sulphuric acid and phosphoric acid, respectively. These acids then dissociate in solution increasing the hydrogen ion content of the blood and thus lowering the pH. Cationic minerals such as calcium, magnesium, potassium and sodium are able to counter the increased acid load because they form metal salts which have a buffering effect on the anionic components that contribute to acidosis. High quality diets are generally rich in cationic minerals and as such the acid-base balance can be maintained. Long-term consumption of low quality diets however increases the acid load of the body and this results in the resorption of cationic minerals from bone to buffer the increasing yields of sulphate and phosphate. Evidence suggest that cationic minerals is supplemental form may benefit bone for this reason.
Bicarbonate ions in the blood act as a buffer against detrimental increases in hydrogen ion concentration (decreases in pH). Bicarbonate can formed endogenously in the body, however, bicarbonate ion concentration can be increased in the blood significantly through the ingestion of sodium bicarbonate. Sodium bicarbonate, is commercially available as baking soda or bicarbonate of soda. The use of sodium bicarbonate in athletes has been shown to be effective at preventing the fall in pH associated with intense extensive. This acidifying effect is due to the dissociation of lactate from skeletal muscle in the blood. Sodium bicarbonate supplements may therefore delay fatigue caused by changed to the acid-base balance. In the same way bicarbonate may improve health through its ability to affect the acid-base balance. For example, because bicarbonate is an effective buffer, dietary bicarbonate may increase calcium retention through a decreased requirement of the resorption of bone tissue for its buffering capacity.
Studies have investigated the effects of bicarbonate ingestion on calcium retention in women in order to assess its usefulness in the prevention of bone disorders such as osteoporosis. For example, in one study1, researchers increased the protein content of a group of women from 44 grams per day to 102 grams per day over the course of a 40 day metabolic ward study. During the last 10 days of the study the women ingested 5.85 grams of sodium bicarbonate along with the higher protein intake. The increase in protein acidified the urine and increased the calcium excretion. However the bicarbonate was effective at reversing this process. However, the pH and the bicarbonate ion concentration of arterial and venous blood were not affected by ingesting bicarbonate. These results suggest that dietary bicarbonate may be effective at improving calcium retention possibly through a mechanism that involves an alkalising effect on the blood. This effect may in turn decrease the resorption rate of calcium from bone tissue.
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