Astronauts' food and drinks are dehydrated or freeze-dried, and packaged to prevent spoiling. Meat undergoes radiation treatment to preserve it. Food is stored in locker trays encased by netting to ensure they do not float away. The astronauts add water from a dispenser to rehydrate the food and they heat it in a convection oven at 320-338 degrees Fahrenheit (160-170 degrees Celsius). It takes about 20 to 30 minutes to prepare the food, about the same amount of time a quick meal takes at home. The astronauts attach their food containers to trays with fabric fasteners, and the trays are connected to the wall or to their laps in order to secure them. Salt and pepper are dispensed as liquids because powder could affect the equipment onboard, and for the same reason tortillas are used instead of bread that could leave crumbs [source: NASA].
Space flight presents particular nutritional challenges. Because astronauts have a reduced number of red blood cells in space, their diets have to contain less iron so that an excess of that mineral won't cause problems later on. Sodium is also limited because too much salt could cause bone loss. Astronauts also take vitamin D supplements because they don't get the sunlight that allows our skin to generate its own vitamin D naturally here on Earth [source: NASA].
Spacewalks outside the space shuttle can last up to seven hours. Each astronaut dons a special spacesuit (worth $12 million) during the spacewalk. This spacesuit, the Extravehicular Mobility Unit (EMU), is equipped with a fruit or cereal bar and an In-Suit Drink Bag (IDB) that holds up to 32 ounces (1.9 liters) of water. The astronaut simply has to turn his head within his helmet to eat or drink. During the spacewalk, each astronaut wears a large, absorbent diaper. Known as the Maximum Absorption Garment (MAG), this diaper collects the astronaut's urine and feces.
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