Vitamin D and its metabolites have clinical significance because they play a critical function in calcium homeostasis and bone metabolism. Although not all of the pathologic mechanisms have been adequately described, vitamin D insufficiency and deficiency, as measured by low levels of 25-OH vitamin D, are associated with a variety of clinical conditions including osteoporosis, falls and fractures in the elderly, decreased immune function, bone pain, and possibly colon cancer and cardiovascular health.2 Apart from inadequate dietary intake, patients may present with low levels of vitamin D if they receive inadequate sunlight.
The astronaut population is potentially vulnerable to low levels of vitamin D for several reasons. Firstly, they may train for long periods in Star City, Russia, which by virtue of its northern latitude receives less sunlight in winter months.
Secondly, astronauts are deprived of sunlight while aboard the International Space Station (ISS). In addition, ISS crew members are exposed to microgravity for prolonged durations and are likely to develop low bone mineral density despite the use of countermeasures. Therefore, closely monitoring and maintaining adequate vitamin D levels is important for the astronaut corps.
- The only supplement NASA gives crews is vitamin D - Sept 2015
- Recommended increasing vitamin D for space flight – NASA Sept 2013
- 1700 IU vitamin D (50000 monthly) helped antarctic explorers – RCT Jan 2012
- 2000 IU daily raised vitamin D levels by 5 nanograms while on submarine patrol – July 2014
Probably astronuats need more than 1,000 IU