$360,000/ hour to operate Space Station $720,000/working hour (assuming work & exercise = 12 hours/day)
Astronauts spend 2 hours a day exercising to prevent bone loss
Probably only work and exercise 12 hours a day, so only 10 hours a day of work
Note: The only supplement NASA gives crews is vitamin D - Sept 2015 2,000 IU daily, which is not enough
I speculate that if astronauts got 8,000 IU of vitamin D daily that:
- Astronauts could spent 1 hour a day more actually working
- each hour of the space station crew costs $720,000
- Astronauts would be healthier – and thus less time off due to sickness
- Less DNA damage from high-energy environment
Vitamin D reduces damage from Cancer radiation treatment by 3X
I had been thinking about the value of a person's time
Then realized that an astronauts time is very costly
Henry Lahore, Founder of VitaminDWiki, Nov 2017
Web - in addition to Vitamin D, astronauts also need Magnesium
Suspect that the water recycling system on Space Station removes Magnesium
- Benefits for bone from resistance exercise and nutrition in long-duration spaceflight: Evidence from biochemistry and densitometry. 2012, Free PDF online
- The nutritional status of astronauts is altered after long-term space flight aboard the International Space Station March 2005, Free PDF online
- Potential renovascular hypertension, space missions, and the role of magnesium 2009. Free PDF online
- The Vitamins you will need to survive a trip to Mars Sardi 2013
Excellent, with many references. Includes Vitamin D and Magnesium -  Download Magnesium and Space Flight - 2016 from VitaminDWiki