Reducing Dietary Acid Load as a Potential Countermeasure for Bone Loss Associated with Spaceflight
- Paper number
IAC-06-A1.2.04
- Author
Dr. Sara Zwart, Universities Space Research Association, United States
- Coauthor
Ms. Sarah M. Watts, Universities Space Research Association, United States
- Coauthor
Dr. Clarence F. Sams, Universities Space Research Association, United States
- Coauthor
Dr. Peggy A. Whitson, Universities Space Research Association, United States
- Coauthor
Dr. Scott M. Smith, Universities Space Research Association, United States
- Year
2006
- Abstract
Along with providing energy and nutrients essential for the body, a diet with an optimal chemical composition could minimize many negative effects of spaceflight on human physiology, including bone loss. We describe here the results of several studies, both spaceflight and ground-analogs, that demonstrate that reducing the dietary acid load has a positive effect on maintenance of bone. The study designs were based on the concept that diet can alter acid-base balance, and the results support ground-based studies showing that metabolic acidosis negatively affects bone.
In the first study, during 60-90 days of bed rest (n = 11), the potential renal acid load of the diet was estimated from the chemical composition of the food, including sulfur-containing amino acids, phosphorus, potassium, calcium, and magnesium. The acid load was positively correlated with urinary markers of bone resorption (P < 0.05); that is, the higher the acid load, the greater the excretion of bone resorption markers.
In the second study in males (30 d bed rest), the ratio of dietary animal protein:potassium was used to estimate the ratio of non-volatile acid precursors to base precursors in the diet. This ratio was positively correlated (P < 0.05) with markers of bone resorption. An increase of 30
In a third study, subjects received either a placebo (n = 6) or an essential amino acid supplement (n = 7; 45 g essential amino acids per day) for 28 d. The supplemented group received about 215
Finally, preliminary spaceflight data provided evidence that less bone resorption occurred in crew members who received potassium citrate (n = 5) during long-duration spaceflight (4-6 months) than those who received placebo or those not in the study (n = 7) (P < 0.05).
Together, these data suggest that reducing acid load, either by ingesting an alkaline salt such as potassium citrate or by altering diet, has the potential to mitigate increased bone resorption during spaceflight, and may serve as a bone loss countermeasure.
- Abstract document
- Manuscript document
IAC-06-A1.2.04.pdf (🔒 authorized access only).
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