During long-duration space flights, astronauts often don’t eat as much as they should, which can cause weight loss and other nutritional concerns, such as low levels of vitamin D. A study released today of astronauts who lived aboard the Russian space station Mir, and counterparts living in seclusion on Earth, has validated a tool for measuring astronauts’ dietary intake during long space flights. “When you are going to spend a few months in space, it’s important to be sure you meet your body’s nutritional needs,” Dr. Scott M. Smith said. One nutrient of particular concern during long-duration space flights is vitamin D, which is important for bone health. The lack of ultraviolet light due to spacecraft shielding takes away the body’s ability to produce this vitamin naturally during space flight. “This is just one example of why food becomes even more important during long space flights.”