1. To determine if the ratio of acid (animal protein) to base (potassium) precursors in the diet is correlated with markers of bone formation and bone resorption during spaceflight.  Specifically, this aim will be addressed by controlling the ratio of animal protein to potassium intake during short-duration spaceflight.
2. To determine the influence of urinary calcium excretion on the predictability of changes in bone metabolism from acid and base precursors in the diet.
3. To determine if the ratio of acid to base precursors in the diet is related to length of time required for recovery from bone mineral loss after spaceflight.  This aim will be addressed during recovery from long-duration spaceflight. 

1) include inflight blood and urine collection

2) expand nominal testing to include makers of normative markers of nutritional assessment

3) add an R+30 session to allow evaluation of postflight nutrition and implications for rehabilitation

1. Exercise countermeasures are currently only partially protective. Nutritional supplements may improve exercise countermeasures effectiveness. Studies will be solicited to test novel nutritional supplements to improve exercise effectiveness in a bed rest flight analog. This will directly address the gaps to minimize exercise time and hardware that is required.

1)   Develop an evidence-based approach to maintain physiological function while simultaneously decreasing total exercise time and volume by development of a novel exercise prescription for use on ISS.  The exercise regimen will use higher intensity resistance exercises and interval aerobic exercise according to the Intramural and extramural experts convened for two workshops held in 2008: the NASA Muscle Workshop in June 2008 and the NASA International Space Station Exercise Prescription Workshop in October 2008.  

2) Include an increase in the intensity and a reduction in the volume of resistance exercises, include very short, but high intensity interval-type aerobic exercises, and start the exercise countermeasures as early as possible in the flight, preferably in the first week. 

1. To investigate the risk of microgravity exposure on long-term changes in bone health and fracture risk.
2. To provide a summary of the current evidence available on potential risk factors for bone loss, recovery and fracture following long-duration space exploration.

This study will describe in each astronaut:

1. How the QCT-measured changes in hip bone BMD and in the cross-sectional areas of cortical and trabecular bone correspond to different mitigating approaches to bone loss, i.e., biochemical or biomechanical, either in combination or singly. 
2. How the above QCT-measured changes in hip bone morphology translate to hip bone fracture loads (aka, “hip bone strength”) as determined by FE Modeling of QCT data.
3. How QCT-measured changes in hip bone morphology during postflight period translate to the recovery of baseline (i.e., preflight) FEM-derived hip bone strength after a mission on-board the International Space Station.

1. Includes in-flight blood and urine collection
2. To provide an ongoing repository of biochemical data to allow operational and research assessments of astronauts on ISS missions.
3. To determine the time course of changes during and after space flight in a broad-based biochemical profile to include biomarkers of nutritional, cardiovascular, musculoskeletal, pharmacological, immunological, and endocrine/general chemistry indices of health and physiology.
4. To evaluate countermeasure effectiveness during and after space flight.
   
   

The dataset from the Nutrition SMO has been used by numerous groups to help identify or explain medical, scientific, and even engineering issues that have occurred during or after ISS missions.  The data have been used by Medical Operations to confirm the effectiveness of 800-IU/d vitamin D supplementation, to determine whether nutrient toxicities existed (secondary to supplement use), to evaluate renal stone risk in crew members who had experienced renal stones post flight, and to evaluate the effects of exercise device use on bone and calcium metabolism.  The ISS Program Office used data from this experiment to determine factors contributing to the Urine Processor Assembly (UPA) failure, and subsequently to make operational decisions for defining forward risk determinations and hardware constraints.  Perhaps most strikingly, the data provide evidence that folate-dependent 1-carbon metabolism may be altered in crew members who experienced vision changes post flight.  These vision changes have been described as the single biggest clinical issue to arise from space flight to date, and the relationships with 1-carbon metabolism intermediates never would have been discovered if a research surveillance protocol was not being conducted.  In this case, data from the Nutrition SMO may guide future countermeasure research and ultimately operational recommendations to minimize risk of vision changes in future crew members. The impact of the data collected to date provide the rationale for continuing this protocol, eliminating some tests while expanding to provide a repository of data to other scientific Disciplines.