**1.3 Nutrition and Hydration**

Preparation, storage, dispensing, and consumption of food in
microgravity. Quantity, quality, variety, appearance, taste, smell,
scheduling.

Storage, dispensing, and consumption of water or other hydration fluids
in microgravity. Color, taste, smell, temperature, quantity, quality,
purity. Multifiltration process, vapor compression distillation, urine
processing.

Water uses (drinking, preparing food, water in food, personal hygiene,
housekeeping, experiments, EVA cooling)

This chapter is designed to provide you with a basic understanding of
the nutrition and hydration options available to space travelers. A
history of "space food" is provided from the 1960's until the present
day, as well as a description of how water is delivered, created,
stored, and used in space. You will be expected to understand
nutritional aspects, such as nitrogen balance, of spaceflight, and you
will be able to describe some of the challenges facing nutritionists as
they look ahead to exploration class missions.

Food is a key part of crew morale and performance. As Napoleon observed,
"An army marches on its stomach," and this is nowhere more true than in
a small group of travelers, far from home, isolated and with few
diversions. The US Navy, which deals with significantly larger groups
than does the space agency, has long experience with submariners that
shows how lack of variety in a menu or poorly prepared food has negative
mission impact.

Indeed, in addition to the decrements in job performance, increased
interpersonal conflicts have also been reported when palatable foods are
in short supply. For these reasons, the Space Food Systems Laboratory at
NASA-Johnson Space Center was created to ensure the proper nutrition and
hydration of American astronauts during spaceflight. Food scientists,
nutritionists, dieticians, and engineers perform research and develop
the best ways to prepare, package, and present food in space.
Nutritional analysis, sensory evaluation, storage studies, and packaging
evaluations are just some of the work performed there.

Despite these efforts to offer space travelers a variety of
nutritionally balanced foods, weight loss during missions remains a
common finding. There is currently no refrigerator for food on the ISS
or Shuttle, and the lack of fresh produce and reliance upon processed
foods may be contributing factors. Work continues to try to improve this
situation, particularly for the ISS crew, along with research into
developing agricultural methods for use on future long duration and/or
exploration missions.

**Eating in Microgravity**

**Variety, Storage, Preparation, Dispensing and Consumption of Food**

Astronauts are scheduled for three meals a day, and nutritionists make
every effort to ensure that the crew's food provides them with a
balanced supply of their required daily calories, vitamins, and
minerals. Processed and prepared foods are the order of the day; Julia
Child would be disappointed, but the galley facilities are very limited,
consisting of a water supply (for rehydrating foods and supplying
drinks) and a small convection oven. Stowage space is also minimal, and
no refrigeration is available, so virtually no cooking is done onboard.
As any chef knows, food preparation can be a messy and time consuming
affair and is unsuited to the operational environment. As a result, all
the menu items are either precooked or preprocessed so as to be ready to
eat. At most, rehydration and heating are required.

Current US menus include a variety of food, such as nuts, peanut butter,
chicken, beef, seafood, candy, rice, and brownies. When international
astronauts fly on the Shuttle, they often bring other foods from their
own countries. For the ISS, its current food system is half US and half
Russian, with plans to add contributions from other International
Partners as their astronauts join the ISS crew. Typical ISS foods
currently include jellied pike perch, grits with butter, honey cake,
beef with barbeque sauce, Russian Rossiyskiy cheese, cinnamon rolls,
lasagna, apple-black currant juice with pulp, granola bar, stewed
cabbage, lemonade, barley kasha, and chicken noodle soup. All ISS
crewmembers taste the food from both countries, and menus reflect their
preferences. \[See Figure One.\] To improve palatability further and
allow individual adjustment of taste, some condiments are available in
single size servings (mayonnaise, hot sauce, mustard, and ketchup),
while liquid forms of salt and pepper are provided in dropper bottles.
\[See Figure Two.\]

Not all foods are available, however. Bread, for example, is not flown
because its crumbs are difficult to manage in the microgravity
environment -- they float around, creating aspiration and ocular hazards
as well as cluttering up the atmospheric scrubbing system. \[Tortillas
are used instead and have proven very popular. See Figure Three.\] In
addition to foods such as bread which are unsuited to the space
environment, there are those which require storage conditions that are
unavailable on current platforms. Since the Soyuz, Shuttle, and ISS do
not contain refrigerators or freezers, foods (such as dairy products and
fresh produce) which require cold storage are unavailable to the crew,
except immediately after launch or resupply vessel docking. Generally
speaking, foods that are either moist or come in a sauce are preferred,
as they permit easy eating in microgravity. Similarly, "individually
packaged" foods, such as M&M candies, are very easy to consume and pose
no housekeeping difficulties.

In an effort to minimize upmass and storage space, many rehydratable
foods are flown. Examples include macaroni and cheese, soup, shrimp
cocktail, cereal (including dry milk powder), eggs, and chicken and rice
casserole. After water is added and the contents mixed, the packaged
food can (if needed) be heated in the oven, then cut open and consumed.
By contrast, commercially available thermostabilized food (i.e. food
that has been heat-processed for preservation) or irradiated food (often
meats) usually require less preparation time. Fruits, tuna, and puddings
are flown in this form and must only be opened and consumed. Even some
entrees are now commercially available in this form: beef tips with
mushrooms, pasta, chicken a la king. As needed, these can be heated in
the oven prior to consumption.

Food packaging must not only provide preservation of the food within,
but also in some cases must prevent the food from floating away during
the meal. Packages are usually flexible, single serving, and disposable.
The flexibility increases ease of use and allows maximum use of stowage
and disposal space. The limited water supplies make dishwashing
impractical, so single-serve disposable containers are the rule. On
future exploration class missions, however, it is likely that new
systems will be needed which make use of recycling rather than disposal.

Pouches are often used to package thermostabilized, irradiated, and
natural form foods, and are easily compressed afterwards for disposal.
Similarly, foods that are flown in their natural form (granola bars,
cookies, nuts) are packaged in flexible pouches or plastic bags, for
easy access. Bowls containing rehydratable foods have detachable lids
with an interface adapter so that galley water can be added. Velcro tabs
on the bottom of the packages and pouches permit it to remain attached
to the meal tray, bulkhead, or crewmember's clothing.

On the Shuttle, meals are stowed in the locker in the order which they
will be eaten, thus simplifying dispensing of food among the crew at
mealtimes. The locker has a contents list on the outside and a net on
the inside to retain its contents while permitting examination. Each
astronaut has a color assigned to his or her position (commander, pilot,
mission specialist 1, mission specialist 2, etc); food trays make use of
this color coded system with dots affixed to each menu item. \[See
Figure Four.\] In addition, an extra 2 days of food per person is also
stowed, in case the mission is extended or weather conditions delay a
return. Given the minimal preparation and the logical storage of the
food trays, meal set up requires only a few minutes on orbit. Even when
rehydration and heating are required, a meal for the entire Shuttle crew
can usually be ready within 30 minutes.

The ISS crew stores most of their food in the Zarya and Node modules.
Morning and evening meals are generally taken communally in the Service
Module, which has a folding table that can accommodate all three
crewmembers (similar to the one used by the Skylab astronauts). Food
warmers that are built into the table can fit the Russian food items,
but the US foods must be heated in a separate warmer. \[See Figure
Five.\] Unlike the Shuttle, which carry their trash back to Earth with
them, on the ISS, trash (including used food packaging) is placed in the
Progress rocket which is eventually jettisoned and burns up on reentry
into the atmosphere.

**Quantity, Quality, Appearance, Taste, Smell, and Scheduling**

In the early space program, there was a great deal of concern about the
ability of crewmembers to eat without aspiration. John Glenn
demonstrated that humans could safely eat in space, but unfortunately he
and the other Mercury astronauts were forced to endure freeze dried and
semi-liquid foods packaged in squeezable aluminum tubes. By the Gemini
program, with its longer missions, improvements had been made; shrimp
cocktail, butterscotch pudding, chicken, and vegetables were some of the
choices available, though there was still no way to have a hot meal. The
Apollo spacecraft were the first to provide hot water and with that came
improved taste and easier reconstitution of freeze dried foods.
Heat-stabilized foods were also first utilized during the Apollo
missions.

The Skylab program had a great deal more habitable space than previous
vehicles and included a dining area, complete with table. Footholds
permitted crewmembers to "sit" together for meals. The large internal
volume also permitted stowage of more foods, and the Skylab menu
included 72 choices. In addition, Skylab is the only vehicle to date
that has included a food refrigerator and freezer.

In contrast to the specially prepared (though minimally appetizing)
foods of Mercury, current Shuttle and ISS menus consist mostly of foods
that are prepared commercially. Several months prior to their mission,
crews sample a variety of foods and select their menus from a variety of
food items, including thermostabilized, rehydratable, irradiated, and
"natural" form. Their choices are also evaluated by the Space Food
System Laboratory personnel to identify and rectify any nutritional
deficiencies.

About a month before Shuttle launch, the crew's food trays are packaged
and stowed in refrigerated conditions. Two to three days prior to
launch, the trays are installed on the orbiter; the day before liftoff,
additional fresh food items are placed into a small locker. (These foods
will be consumed early in flight.) For ISS crewmembers, their food is
often sent up before they are, on previous Shuttle or Progress missions.
As a result, by the time they arrive, their food will be waiting for
them. Unlike Shuttle crews, who often have a choice as to whether they
want their menus to repeat over the course of their mission, ISS crews
operate on a 8 day menu cycle (i.e., every eight days, the menus repeat
themselves).

**Protein Balance, Vitamins, and Electrolytes**

Many of the physiological adaptations to weightlessness may affect (or
be affected by) nutritional intake. Although it is unlikely that an
adequate diet will prevent all of these changes, it is distinctly
possible that consuming too few nutrients can worsen the adaptations or
at least delay the astronaut's post-flight recovery.

Both the Russian and American space program have consistently documented
weight loss in their crews during spaceflight. During the Mir program,
up to 15% body mass losses were seen over the course of a 3-4 month
mission. Approximately 1% of the loss can be attributed to water loss,
due to the cephalad fluid shifts and redistribution associated with
microgravity, the rest is due to loss of bone, muscle, and adipose
tissue. This loss in lean body mass is particularly concerning since it
is associated with an increased risk of skeletal fractures and thus
augments the microgravity-related effects on bone.

When adipose and muscle tissue losses are seen, particularly in the
setting of lower caloric intake, inadequate nutrition is the default
diagnosis. The stressful, isolated environment of spacecraft, early
space motion sickness, along with the limited menu choices and altered
taste sensation have been some of the factors frequently quoted to
explain crew's weight loss in space. The microgravity-associated
muscular atrophy (particularly in the leg muscles where there are
significant decreases in muscle mass and performance) and bone loss
(especially in weight-bearing bones) have also been implicated.

The protein balance during spaceflight is particularly problematic.
Decreased body proteins are associated with impaired performance,
decreased immune function (which is also a documented effect of space
flight), and clinical depression. Both caloric and protein intakes are
traditionally lower in space, however loss of body mass has occurred
even in the presence of adequate nutritional intake. This suggests that
protein balance may be significantly altered in the microgravity
environment. Studies have shown an increased whole body protein turnover
during space flight, but the etiology and relevance of this finding
remains unclear.

One major problem with the consumption of processed foods on orbit is
that they tend to be high in sodium. (One study on the Shuttle
documented dietary intakes above 4000 mg per day.) Terrestrial research
has demonstrated that excessive sodium increases bone turnover and
urinary calcium excretion, which are already abnormal in space due to
the microgravity environment. There is thus concern that the processed
foods may contribute to (or worsen) the bone demineralization (and
subsequent increased renal stone risk) during flight.

Research is underway into nutritional intervention strategies in the
hopes that they may be able to improve bone health and decrease renal
stones through control of the nutrients that affect bone metabolism:
sodium, calcium, protein, phosphorus, vitamin D. Although these findings
are particularly relevant for ISS and exploration class missions, since
clinically significant deficits in bone mass are not visible until after
several weeks of microgravity, they may have implications even for
Shuttle flights, as biochemical changes have been found to begin within
hours of weightlessness.

Further complicating the picture is the fact that long duration
astronauts do not receive an adequate amount of sunlight (particularly
the 290-315 mid-ultraviolet range which is needed for cutaneous
production of vitamin D) and are thus at risk for vitamin D deficiency.
Currently, vitamin D supplements are recommended for ISS crewmembers,
although their use during ground based studies and Skylab missions did
not demonstrate a clear benefit. Interestingly, vitamin K
supplementation in a single astronaut resulted in improved markers of
bone formation. Given the microgravity-associated changes in the
gastrointestinal tract flora (where vitamin K is absorbed), it is not
unreasonable to assume that this may have an effect on vitamin
metabolism. Further investigation into the value of vitamin K
supplementation may have implications for not only bone health but also
coagulation pathways.

In addition to sodium, the current crews also consume higher than
recommended amounts of iron. Because red blood cell mass is decreased in
space, while iron storage is increased, expert panels have advised
limiting daily iron intake to under 10 mg per day to prevent excessive
iron sequestration in body tissues. However, neither the Russian nor US
programs can currently achieve that level, and 20 mg of iron is the
daily intake with the current menus.

Other nutrients, such as water-soluble vitamins, minerals, and
electrolytes, are generally considered well handled by the current
diets. However, as part of the ongoing efforts to ensure that a proper
balanced diet is being consumed, particularly on long duration flights,
crews are asked to fill out Food Frequency Questionnaires on a weekly
basis. Nutritionists then review these and make recommendations for any
needed improvements to the crew's diets.

**Fluid Consumption in Microgravity**

**Storage and Dispensing**

Systems for storage of water in microgravity environments are
significantly more complex than terrestrial systems. \[See Figure Six.\]
Normally, gravity ensures that water stays in one place, separates from
air, and moves down an incline. None of these things occur in
microgravity, necessitating enclosed containers, pressurized lines, and
other methods for air-fluid separation. In microgravity, it is much
easier to force the water out of flexible walled containers as they can
be squeezed or rolled, much like toothpaste tubes on Earth.
Unfortunately, they tend to have shorter lifespans than their rigid
counterparts. Some systems make use of both; in the Soyuz, for example,
a rigid walled tank holds a flexible bladder containing the water, and
mouth suction is used to draw water out as required.

Early US spacecraft (Mercury and Gemini) used municipal water supplies
on board. On Apollo, the fuel cells created potable water, to which the
crew daily added chlorine to avoid microbial growth. Iodine was the
bactericidal agent on Skylab; crews regularly added iodine to the water
tanks during the course of the mission. On the Shuttle, iodine remains
the bactericidal agent, at a concentration of 1-2 mg/liter. Silver is
used by the Russians to prevent microorganism growth; the ISS water
contains 0.2 mg of ionic silver per liter.

**Color, Taste, Smell, Temperature, Quantity, Quality, and Purity**

For many years, the color, smell, and taste of water in space has left
much to be desired. Tang, that drink mix forever linked to the early
American space program, was actually created to mask the metallic taste
of the Apollo spacecraft's water, although additional minerals and trace
nutrients were also added. \[See Figure Seven.\] The Shuttle's use of
iodine not only led to complaints regarding taste, palatability, and
color of the water onboard, but the iodine content of the water actually
elevated thyroid stimulating hormone levels. Now, an iodine removal
system has been added to the galley water supply so that it is removed
from the water just prior to consumption.

The silver system used on the ISS has had perhaps the fewest negative
comments to date, but since the ISS does not provide cold water (as the
Shuttle does), plain water is infrequently drunk. Rather, drink mixes
(tea, coffee, etc) or soups (bouillon, broths, soups) are widely used.

Water quality can be compromised through biological ("brown sludgy
water") or chemical ("green glowy water") contamination (or both). On
short duration missions, preflight verification of water quality is
considered sufficient, but on longer flights, additional testing is also
required, as contaminants could enter the storage containers during the
course of the mission. \[See Figure Eight.\] Water pH, conductivity, and
total organic carbon content are the parameters currently studied to
ensure acceptable quality, although, for exploration class missions, the
ability to perform in-flight spectrographic analysis will likely be
needed.

**Consumption of Water and Other Hydration Fluids**

Humans typically consume 3 kg of potable water per day for drinking and
cooking while up to 26 kg of non-potable water is used for hygiene
activities (washing, showering, laundry). Potable water in spacecraft
has traditionally come from fuel cell production (Apollo, Shuttle),
stored quantities (Skylab, ISS), and/or reclamation systems (Mir, ISS).

**Drinking**

Space travelers consume many types of beverages in space, in part
because microgravity is a renal stone-forming environment, and it is
thus particularly important for space travelers to consume adequate
amounts of fluids. Coffee, tea, orange juice, fruit punch, cider,
lemonade, and fruit juices are available on current spacecraft, though
in powdered form. \[See Figure Nine.\] To increase shelf life, drinks
are packaged in foil laminate, with interfaces for the galley water
nozzle and a drinking straw.

Cold water is available on the Shuttle, which assists in palatability,
but on the ISS crewmembers only have ambient, warm, and hot water
available.

**Preparing Food**

Dried foods are used on ISS as well as Shuttle and require water for
their preparation as described above. Otherwise, little water is
required for food preparation as no "cooking" occurs on board.

**Water in Food**

The water content in food is an important part of the water balance for
crew members. It will become even more critical as the efficiency of
water reclamation systems improves (see below).

**Water Reclamation and Production (Multifiltration Process, Vapor
Compression Distillation, Urine Processing)**

Even ancient explorers knew it was madness to set out on a voyage
without adequate supplies of water, and nothing has changed over the
intervening millennia. Water remains a critical requirement for all
manned space missions, yet -- so far as we know -- potable water exists
nowhere beyond Earth. Thus, unlike those early adventurers who had hopes
of finding new water sources along their path, space travelers must
either bring their water supplies with them or create more along the
way. On the Shuttle, this is addressed by the vehicle's fuel cells which
produce water as a byproduct of its electricity generation. The ISS,
however, uses solar power to generate its electricity, and as a result,
it does not have an abundance of water. Unpalatable as it may be to
consider, water reclamation -- from sweat, exhalations, and even urine
-- is a critical aspect of long duration mission planning and is likely
to become even more so as exploration missions to the moon and Mars are
developed.

Water is routinely delivered to the ISS via the US Shuttle (often in 90
lb, duffle bag-like "contingency water containers") and Russian
"Progress" rockets (in large tanks), but doing so is expensive and
creates a dependency on ground supplies, rather than developing ISS
autonomy. \[See Figure Ten.\]

It was in part due to this dependence upon Shuttle-delivered water that
forced a decrease in ISS crew size following the grounding of the
Shuttle crew in February 2003, after the Columbia disaster. In the
absence of regular visits from the Shuttle to replenish water supplies,
a three person crew could not be sustained aboard the ISS.

No water reclamation system is 100% efficient, so for the foreseeable
future, there will always need to be some stored supplies. \[See Figure
Eleven.\] The goal, particularly for exploration class missions, is to
minimize this stowage to the greatest extent possible. If, for example,
system efficiency can be improved to roughly 95%, then the water
contained in the food supply would be sufficient to replace the water
lost to the environment. Reclaimed water contains a variety of
contaminants, ranging from dead skin cells to urea and from soap residue
to bacteria, which the reclamation system must remove.

The Russian segment of the ISS currently contains a water collection
unit that captures humidity from the cabin environment, then pumps the
water through ion exchange resins and activated charcoal. The water's
electrical conductivity is then tested. If the conductivity is low, then
the water is sufficiently pure to be returned to the potable water
supply. If it is high, the system is deactivated and the crew
investigate. Water leftover from food preparation and personal hygiene
goes through the same system, though urine is sent to a different
system, to be used in the creation of oxygen via electrolysis.

American engineers are currently developing a water recycling system
that will collect water from fuel cells, urine, oral hygiene, and hand
washing, as well as humidity from the air. The incorporation of this
unit into the ISS is currently unscheduled. The system is even designed
to reclaim water from the experimental animals that may one day live
aboard the ISS. \"Lab animals on the ISS breathe and urinate, too, and
we plan to reclaim their waste products along with the crew\'s. A full
complement of 72 rats would equal about one human in terms of water
reclamation,\" says Layne Carter, a water-processing specialist at the
MSFC.

The purity of such reclaimed water would be quite high, and it would be
considered potable (though not sterile or injectable-grade). \"The water
that we generate is much cleaner than anything you\'ll ever get out of
any tap in the United States,\" says Carter. \"We certainly do a much
more aggressive treatment process (than municipal waste water treatment
plants do). We have practically ultra-pure water by the time our
water\'s finished.\"

The water purification machines utilize a three-step process to treat
the waste water. Initially, a filter removes particles and debris, then
the water passes over \"multi-filtration beds" that remove organic and
inorganic impurities. Lastly, a catalytic oxidation reactor, similar to
the one used in the atmosphere processing system, removes volatile
organic compounds and kills bacteria and viruses.

**Non-Potable Water Uses**

**Personal Hygiene**

With water a potentially mission-limiting consumable, personal hygiene
in space is different from that on Earth. Water pressure on the ISS, for
example, is about half that in a US household. However, for morale
purposes as well as basic hygiene concerns, washing, shaving, and
toothbrushing must be available for the crews, particularly on long
duration missions. Although both Mir and Skylab had showers on board,
none of the current spacecraft do; instead, sponge baths, using wet
washcloths, are the norm. This reduces the quantity of water required
from 50 liters for the average terrestrial shower to 4 liters for the
average ISS "bath". Handwashing similarly uses only about 10% of the
water in space as on Earth.

Neither the toilet on the ISS nor the one on the Shuttle use water, the
way terrestrial toilets do. Rather, the ISS commode collects solid and
liquid waste in a bag with a permeable liner. The liquid is pulled off
for use in the reclamation system, while the solids are sealed in the
bag and stored in the toilet until it is removed and packaged in the
Progress with other trash. On the Shuttle, a centrifugal system collects
solid waste, while a hose-like device is used to capture urine.

**Housekeeping**

Laundry and other housekeeping duties are also limited by both the water
supplies and the microgravity environment. Ken Bowersox described how he
washed a pair of shorts during his mission on the ISS (video available
at http://spaceflight.nasa.gov/ gallery/video/station/
expedition6/category/ndxpage11.html): 'The shorts have been wetted with
condensate and we added some soap, just regular bar soap, to take the
oils out, and we just sort of squeeze it around in a \[plastic\] bag.
You squeeze the condensate in and out of the clothes, just like in a
washing machine. The shorts really soak up that water, so the next
\[thing we do\] is to take some towels and dry out all that condensate
that's soaked with soap." Next, he repeats the process with some fresh
condensate water to provide a "rinse cycle". Then the shorts are
fastened on a 'clothesline' and within 3 hours, they have dried: "It's
amazing how quickly the water gets soaked up into the air... They look
like they're fresh out of the clothes drier at home!" Despite Captain
Bowersox's inventiveness, space travelers do not routinely wash their
clothing. Instead, sufficient supplies are to allow the crew to change
their pants weekly while shirts, socks, and underwear are changed every
two days.

Cleaning supplies, such as absorbent wipes, are provided for the crew to
swab down the surfaces of the spacecraft, though they can also make use
of wet towels if they prefer. Obviously, this is less of an issue on
short duration flights in Shuttle and Soyuz, though even there, it may
be needed occasionally. A vacuum is flown aboard the ISS to further
assist with "housecleaning". This can be particularly helpful for
cleaning grates, filters, and fans.

**Experiments**

Experiments may also make use of on-board water supplies. This will
naturally vary from experiment to experiment, and preflight planning
will take the research needs into consideration. Some will require
potable water from the spacecraft's supply, others may send along their
own separate supply in the same locker or rack. Agricultural projects,
such as the growing of wheat or onion plants in space, are examples of
such research.

**Temperature Control During EVA**

**A liquid cooling garment (LCG) is worn by the crew during EVA. \[See
Figure Twelve.\] The American spacesuit (EMU) makes use of this device
to ensure that the heat generated during a spacewalk, by both the human
and the suit's equipment, is adequately controlled. The LCG consists of
a garment, rather like long underwear, which contains yards of
water-containing coolant tubes. The water, traveling close to the skin,
removes heat from the body, then is chilled through a thermoelectric
cooler before being circulated back through the suit. During the Apollo
missions, when the astronauts were very active on the Moon, the LCG
could remove 500BTU/hr of heat stress. An LCG is also worn during
Shuttle launch and reentry, to diminish the thermal stress associated
with the Launch and Entry Suits, which are very hot to wear. Following
adoption of the LCG, crew members have reported a significant increase
in comfort and decrease in post-flight orthostasis.**

**[References and Suggested Readings:]{.underline}**

1\) DeHart, RL and Davis, JR. (Eds.). (2002). [Fundamentals of Aerospace
Medicine, 3^rd^ Edition.]{.underline} Philadelphia: Lippincott Williams
& Wilkins.

2\) MR Barratt and SL Pool (Eds.). (in press). [Principles of Clinical
Medicine for Space Flight.]{.underline} New York: Springer Verlag.

3\) Clement, G. (2003). [Fundamentals of Space Medicine. Space
Technology Library.]{.underline} El Segundo: Microcosm Press.

4\) Harding, R. (1989). [Survival in Space.]{.underline} London:
Routlege.

5\) Parker, JF and West, VR. (1973). [Bioastonautics Data Book, 2^nd^
Edition.]{.underline} Washington DC: NASA Scientific and Technical
Information Office.

6\) Larson WJ and Pranke LK (Eds.). (1999). [Human Spaceflight: Mission
Analysis and Design.]{.underline} New York: McGraw Hill.

7\) Stine GH. (1997). [Living in Space: A Handbook for Work and
Exploration Stations Beyond the Earth's Atmosphere.]{.underline} New
York: M. Evans and Company.

8\) *Nutrition* 2002; 18 (10): 793-935.

9\) Lane HL and Schoeller DA. (Eds.) (2000). [Nutrition in Spaceflight
and Weightlessness Models.]{.underline} New York: CRC Press.

10\) "Water on the Space Station", a Science@NASA story,
<http://spaceflight.nasa.gov/living/factsheets/water2.html>

11\) Space Food,
<http://spaceflight.nasa.gov/living/spacefood/index.html>

12\) "Space Food", October 2002, FS-2002-10-079 JSC document,
http://spaceflight.nasa.gov/spacenews/factsheets/pdfs/food.pdf

13\) "Nutritional Status Assessment for Extended Duration Space Flight",
JSC Document #28566 Revision 1