The effect of weightlessness on the human skeletal system is one of the greatest concerns in safely extending space missions [1–11]. The ability to understand and counteract weightlessness-induced bone mineral loss will be vital to crew health and safety during and after extended-duration space sta- tion and exploration missions [1–7]. Research on bone mineral loss during space flight has gone on for more than half a century, and recent studies have shown significant progress in developing coun- termeasures that have proved to be effective, including good nutrition and exercise. We review the history of this research here and provide a summary of recent and ongoing studies, including efforts to counteract bone and calcium loss resulting from weightlessness. Unfortunately, the most obvious nutritional countermeasure—providing excess calcium—does not protect against bone loss [12]. This result is likely related to the decreased calcium absorption observed in space flight and in ground-based models [13–16]. Phosphate supplementation was also ineffective at reducing calcium excretion [17]. Combination therapy with calcium and phosphorus was also unsuccessful at mitigating bone loss and hypercalciuria [18]. Other nutrients, specifically sodium, protein, potassium, vitamin K, and omega-3 fatty acids, have also been proposed and/or tested as bone loss countermeasures [19], and are discussed in more detail below.
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http://link.springer.com/chapter/10.1007%2F978-1-4939-2001-3_41#page-1