Dietary acid load and bone turnover during long-duration spaceflight and bed rest

Zwart, Sara R.; Rice, Barbara; Dlouhy, Holly; Shackelford, Linda; Heer, Martina; Koslovsky, Matthew D.; Smith, Scott M.

doi:10.1093/ajcn/nqy029

Cited by 30 publications

(26 citation statements)

References 52 publications

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“…Articles included for meta-analysis. We selected 25 articles for meta-analysis, including 12 studies that reported bone density measures before and less than a week after a spaceflight 1,14-23 , 14 studies that contained data on biochemical bone markers [24][25][26][27][28][29][30][31][32][33][34][35][36] , and one study that reported both 37 . The final dataset contained data for~189 astronauts (the number is approximate due to remaining uncertainty in astronaut identification), with bone density measurements and biochemical bone markers available for~148 and~124 astronauts, respectively.…”

Section: Publications On Bone Health In Astronautsmentioning

confidence: 99%

A systematic review and meta-analysis of bone loss in space travelers

et al. 2020

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Bone loss in space travelers is a major challenge for long-duration space exploration. To quantify microgravity-induced bone loss in humans, we performed a meta-analysis of studies systematically identified from searching Medline, Embase, Web of Science, BIOSIS, NASA Technical reports, and HathiTrust, with the last update in November 2019. From 25 articles selected to minimize the overlap between reported populations, we extracted post-flight bone density values for 148 individuals, and in-flight and postflight biochemical bone marker values for 124 individuals. A percentage difference in bone density relative to pre-flight was positive in the skull, +2.2% [95% confidence interval: +1.1, +3.3]; neutral in the thorax/upper limbs, −0.7% [−1.3, −0.2]; and negative in the lumbar spine/pelvis, −6.2 [−6.7, −5.6], and lower limbs, −5.4% [−6.0, −4.9]. In the lower limb region, the rate of bone loss was −0.8% [−1.1, −0.5] per month. Bone resorption markers increased hyperbolically with a time to half-max of 11 days [9, 13] and plateaued at 113% [108, 117] above pre-flight levels. Bone formation markers remained unchanged during the first 30 days and increased thereafter at 7% [5, 10] per month. Upon landing, resorption markers decreased to pre-flight levels at an exponential rate that was faster after longer flights, while formation markers increased linearly at 84% [39, 129] per month for 3-5 months post-flight. Microgravity-induced bone changes depend on the skeletal-site position relative to the gravitational vector. Post-flight recovery depends on spaceflight duration and is limited to a short post-flight period during which bone formation exceeds resorption.

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Section: Publications On Bone Health In Astronautsmentioning

confidence: 99%

A systematic review and meta-analysis of bone loss in space travelers

et al. 2020

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“…Our findings will be useful to investigators conducting clinical or epidemiologic studies that examine potential relationships between the dietdependent acid-base load and human health and disease, 14 exercise performance, 25 or space flight applications. 15 In this study, we used dietary equations to estimate NEAP and found that a number of these calculations accurately predicted their equivalent biochemical measure. In line with previous reports, we found that NEAP R accurately estimated NEAP, 7,16 and for the first time it was observed that NEAP L did as well.…”

Section: Discussionmentioning

confidence: 97%

“…[11][12][13] Clinical and epidemiologic studies routinely rely on estimates of the diet-dependent acid-base load to investigate potential relationships to human health and disease. 14,15 However, a limited number of studies have evaluated the accuracy and precision of estimates of PRAL, NEAP, and their contributors. The accuracy of a measurement is how close a result comes to the true value.…”

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confidence: 99%

Performance of Predictive Equations and Biochemical Measures Quantifying Net Endogenous Acid Production and the Potential Renal Acid Load

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Banerjee

et al. 2020

Kidney International Reports

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Introduction: A limited number of studies have assessed the accuracy and precision of methods for determining the net endogenous acid production (NEAP) and its components. We aimed to investigate the performance of methods quantifying the diet dependent acid-base load. Methods: Data from metabolic balance studies enabled calculations of NEAP according to the biochemical measures (of net acid excretion [NAE], urinary net endogenous acid production [ U NEAP], and urinary potential renal acid load [ U PRAL]) as well as estimative diet equations (by Frassetto et al., Remer and Manz, Sebastian et al., and Lemann) that were compared among themselves in healthy participants fed both acid and base forming diets for 6 days each. Results: Seventeen participants (mean AE SD age, 60 AE 8 years; body mass index, 23 AE 2 kg/m 2) provided 102 twenty-four-hour urine samples for analysis (NAE, 39 AE 38 mEq/d [range, À9 to 95 mEq/d]). Bland-Altman analysis comparing U NEAP to NAE showed good accuracy (bias, À2 mEq/d [95% confidence interval {CI}, À8 to 3]) and modest precision (limits of agreement, À32 to 28 mEq/d). Accurate diet equations included potential renal acid load (PRAL) by Sebastian et al. (bias, À4 mEq/d [95% CI, À8 to 0]) as well as NEAP by Lemann et al. (bias, 4 mEq/d [95% CI, À1 to 9]) and Remer and Manz (bias, À1 mEq/d [95% CI, À6 to 3]). Conclusions: Researchers are encouraged to collect measures of U PRAL and U NEAP; however, investigators drawing conclusions between the diet-dependent acid-base load and human health should consider the limitations within all methods.

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“…The mechanism of the effect of protein and sodium on bone are likely similar, with both contributing to the acidogenic potential of the diet, leading to bone dissolution 91 , 92 . This effect was recently documented in a diet and bone health study on ISS, where the acidogenic potential of the diet correlated with post-flight bone losses 93 . The data from terrestrial research, along with the more limited spaceflight research, clearly identifies nutrition as important in maintenance of bone health and in the mitigation of bone loss.…”

Section: Inadequate Food and Nutritionmentioning

confidence: 96%

Red risks for a journey to the red planet: The highest priority human health risks for a mission to Mars

et al. 2020

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NASA’s plans for space exploration include a return to the Moon to stay—boots back on the lunar surface with an orbital outpost. This station will be a launch point for voyages to destinations further away in our solar system, including journeys to the red planet Mars. To ensure success of these missions, health and performance risks associated with the unique hazards of spaceflight must be adequately controlled. These hazards—space radiation, altered gravity fields, isolation and confinement, closed environments, and distance from Earth—are linked with over 30 human health risks as documented by NASA’s Human Research Program. The programmatic goal is to develop the tools and technologies to adequately mitigate, control, or accept these risks. The risks ranked as “red” have the highest priority based on both the likelihood of occurrence and the severity of their impact on human health, performance in mission, and long-term quality of life. These include: (1) space radiation health effects of cancer, cardiovascular disease, and cognitive decrements (2) Spaceflight-Associated Neuro-ocular Syndrome (3) behavioral health and performance decrements, and (4) inadequate food and nutrition. Evaluation of the hazards and risks in terms of the space exposome—the total sum of spaceflight and lifetime exposures and how they relate to genetics and determine the whole-body outcome—will provide a comprehensive picture of risk profiles for individual astronauts. In this review, we provide a primer on these “red” risks for the research community. The aim is to inform the development of studies and projects with high potential for generating both new knowledge and technologies to assist with mitigating multisystem risks to crew health during exploratory missions.

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Dietary acid load and bone turnover during long-duration spaceflight and bed rest

Cited by 30 publications

References 52 publications

A systematic review and meta-analysis of bone loss in space travelers

A systematic review and meta-analysis of bone loss in space travelers

Performance of Predictive Equations and Biochemical Measures Quantifying Net Endogenous Acid Production and the Potential Renal Acid Load

Red risks for a journey to the red planet: The highest priority human health risks for a mission to Mars

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