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FOOD AND NUTRITION IN SPACE
Robert W. Phillips
LEARNING OBJECTIVES
To understand the differences between providing food to people on Earth and those in
space both from the standpoint of diet and available foods as well as nutritional
requirements and utilization.
To understand how space foods have developed and changed since the beginning of space
flight and what may occur in the future as the space program becomes more mature.
To understand some of the limitations associated with providing food for astronauts on
both short and long term missions.
INTRODUCTION
An adequate food supply and proper nutrition will be an increasingly important aspect of
space flight as journeys away from the Earth’s surface increase in duration. From a
nutritional perspective it is a relatively trivial matter to go on a two-week low earth orbit
mission on the Space Shuttle. Conversely a 3-6 month stay on a space station or even
more extended journey to Mars or a moon base will require more significant nutritional
input. Such input must not only consider the actual nutrients required during spaceflight
but also be designed to satisfy the esthetic components of our diets here on Earth, so that
the crews will be able, at least to an extent, to look forward to an interesting and varied
cuisine while they are away from the Earth’s surface. This will have the added benefit of
increasing food consumption. Decreased food intake and consequent body weight loss
has been a problem since the inception of space flight. Some generalizations can be made
with regard to space diets. In general they have decreased fat and increased carbohydrate.
Most diets have a decrease in fiber, which sometimes leads to constipation. On earlier
short missions with inadequate or absent toilet facilities and no privacy this was not a
serious problem. Protein content of diets has for the most part been similar to Earth diets.
Our understanding of eating and drinking has greatly increased since the “pre-spaceflight”
days when one of the serious considerations was whether people could effectively
swallow in space. That particular concern was rapidly alleviated. Today, knowledge of
specific nutritional differences between Earth and space are fragmentary. Yet the
provision of an adequate diet will be an essential component of human space exploration.
On short term missions or missions with frequent resupply the Space Shuttle, The
Russian MIR space station or the new International Space Station (ISS) currently being
constructed in low Earth orbit, food will be prepared on Earth and shipped up ready to eat
or requiring only minimal preparation
As space flight becomes a more mature endeavor and long duration missions are planned
there will be a gradual shift from ready to eat to food supplied from Earth to production,
processing, preparation and recycling of nutrients in a closed loop environment. This
process is currently designated as Advanced Life Support (ALS) in NASAese as it
involves not just the production of food materials but regeneration of oxygen and potable
water by biological instead of physical-chemical systems.
BACKGROUND
In the very early days of short duration flights nutrition was of minimal concern. As the
space program evolved into longer missions food became a more central element. There
are a number of ancillary effects on the human body and environmental changes that
relate directly or indirectly to food intake and needs.
From an environmental perspective there may be limited storage, no refrigeration and
scant facilities for meal preparation. Imagine in today’s culture spending several weeks
or longer without access to refrigeration and completely dependent on prepackaged or
dehydrated food. Sounds like an extended camping trip. Other aspects of the
environment include microgravity (ug) which has significant effects on the body, a greatly
increased level of carbon dioxide in the atmosphere up from a normal 0.03-0.04% to
anywhere from 0.3-1.0% or higher under certain circumstances. Radiation exposure is
increased, particularly on missions away from Earth’s protective magnetosphere. Normal
circadian or diurnal rhythms may be disrupted due to changes in light dark cycles.
A number of psychological factors may also effect food intake, for instance: isolation,
small group interactions inability to acquire personal space or time in tight living
quarters, work overload. All of the above may contribute to psychological stress and may
modify food desire or acceptance.
From a physiological perspective there are number of body changes that may have a role
in modifying food intake. Early ug induced fluid shifts and changes in blood and total
body water volume are well documented. Gastrointestinal function may be altered due to
changes in microflora and lack of gas separation in stomach and intestine. Decreased
gastrointestinal content transit time has been noted and there may be changes in blood
flow to the intestinal cells. Whether these effects modify nutrient absorption is not
documented at this time. Space motions sickness is often present in the first several days
of space exposure which acts to decrease food consumption. There are several postulated
causes of this malady. The fluid shifts to the upper body may effect the central nervous
system receptors that control gastric unease and vomiting. A more likely explanation is
the changes in vestibular receptors in the inner ear due to lack of a gravitational vector.
Input to the hair cells are dependent on gravity for normal identification of the down
vector. Lack of this normal otolith stimulation coupled with varying visual input may
create mixed and misleading sensory stimuli resulting in a condition very analogous to
motion sickness here on Earth. It is often termed sensory conflict because different
senses are stimulated in a non-coherent fashion.
All in all there are a number of physical and biological influences that may effect nutrient
intake and nutritional needs, ranging from intensive work schedules relatively limited and
repetitive diets and major physical, psychological and physiological changes
FOODS PAST AND PRESENT
The development of space foods have come a long way since the early Mercury flights
when it was not even clear that humans could swallow while in spaceflight. Some of the
criteria established for space foods are listed on slide 18. Of course it is not enough just
to provide food for astronauts the food must be appetizing, and the crew must have time
to consume the food.
Early Mercury capsule food did not require any preparation, It was launched as bite sized
energy dense units. Or stored in toothpaste like tubes i.e. applesauce which was the first
food consumed in space by John Glenn.
As the program continued with the advent of the two person Gemini spacecraft and
longer missions, food was still completely prepared and ready to eat. It provided 2500
kcal/person/day.
In the Apollo program missions were even longer and there was a marked change in the
food system. One basis for this was that water no longer had to be carried into space as
drinking water but instead was produced in the fuel cells that provided energy for the
spacecraft. Because potable drinking water was generated while in space there was little
rationale for sending up water in the food. Instead a switch was made to prepackaged
dehydrated foods. On these longer missions some irradiated and canned foods were
provided. This also brought the addition of utensils to eat with and spoonbowl packaging
so that eating a meal was somewhat more normal. On the lunar surface food bars were
provided inside the space suits.
The next really major improvement in space foods came with Skylab. The lab was
boosted into low Earth orbit using the Saturn V rocket which was used to launch the
Apollo Astronauts to the moon. Over a two year period there were three, 3 man crews
present on Skylab for varying times. Some of the very different factors with Skylab food
were that there were both refrigerators and freezers as well as food warmers present on
the Lab. All planned food and water was sent into space with the initial launch, it
included canned food as well as specialty items like steak, lobster and ice cream. In the
same era Russia was developing its first space stations they had a parallel increase in food
types.
There was a break in American spaceflight until the Space Shuttle was developed and
began to be used in the early 1980’s. The Space Shuttle again used fuel cells to provide
energy and potable water was produced as a byproduct. There are no refrigerators and
freezers on the shuttle so that most of the food is either canned or dehydrated. Some
irradiated food is used as well as semi-moist and natural foods. In the middeck of the
shuttle there is a galley which has a convection oven as well as a rehydration station using
either hot or cold water depending on the food or drink to be rehydrated. The total menu
choices were greatly increased and individual crew members could choose their own
menu within the limits of a balanced diet. Free choice condiments were also available.
Flour tortillas largely replaced bread due to the lack of crumbs generated which are hard
to manage in ug. As foreign astronauts have traveled on the Space Shuttle they have made
some of their thermostabilized foods available to the program. Some of the more
interesting choices are French.
Shuttle-MIR was a special program planned as a prelude to the International Space
Station to give American Astronauts more experience with long term missions. The six
Shuttle-MIR missions ranged from 111-184 days. The MIR space station does not have
refrigerators or freezers so that most food is dehydrated, thermostabilized, intermediate
moisture, natural or snacks. There is a galley that contains a heating and rehydration
station. The food provided 3000 kcal/crew member/day and had increased variety
because it included both American and Russian food items. Most of the potable water
was recycled on MIR. Some fresh foods were available at intervals when resupply
occurred with the arrival of the unmanned Russian Progress space ship or the shuttle.
The next step in space food will come with the completion of the International Space
Station (ISS), currently planned for the year 2004, although the first portions of the ISS
are already in orbit. It will be completed, at least from the perspective of crew size and
habitability when the United States Habitat module is launched and outfitted. The habitat
will contain the galley and eating area as well as an exercise station. Slide 39. Once
again there will be refrigerators and freezers available as well as ambient temperature
storage for foods. There will be a microwave/convection oven. Frozen items will include
entrees, vegetables, baked goods and desserts. The refrigerator will include fresh and
fresh treated fruits and vegetables. Some dairy products will be available as well as
extended shelf life
produce. There will be a 30-day repeating menu with individual choice of menu within
the constraints of nutritional sufficiency. The food will be identified with bar codes
which will include food type, quantity remaining in storage and identify the consumer.
Although all menu items have not been developed there will undoubtedly be a greater
variety due to the broad international flavor of the crew, including American, Russian,
European, (multiple countries) Japanese, Canadian and Brazilian members. The basic
plan for ISS food is to make it as Earth-like as possible with a great deal of variety and
ability to choose specific foods.
One significant difference between food to be consumed in space and Earth food is the
more common and generalized use of irradiation on a variety of space foods to ensure that
they have increased shelf life regardless of storage temperature. This is an effective
means for sterilizing without the changes in taste and flavor that are associated with heat
treatment. A negative aspect of radiation sterilization for space foods is that the process
will destroy some B vitamins, and decrease the content of antioxidants which would be of
particular concern for long term missions away from Earth’s magnetosphere. Here in the
United States irradiation is commonly used to sterilize spices from foreign countries, but
the process is not in wide use yet for meats or other products, due principally to consumer
concerns regarding residual effects of radiation in the food. Interestingly people are not
concerned with having contact with companions that have been x-rayed, or eating food
that has been heated or cooked by microwave radiation.
The first irradiated foods were used in the Apollo program and continued through Skylab
and the Shuttle program. It is anticipated that radiation sterilization will also be used on
the ISS to extend shelf life and for longer lunar and interplanetary missions.
PHYSIOLOGICAL CHANGES IN SPACE FLIGHT
With the possible exception of the immune system body changes that occur after entering
microgravity represent normal homeostatic responses to a new environment. The body’s
control systems recognize the lack of gravity and begin to adapt to this unique situation,
not realizing that the ultimate plan is to return to 1G after a transient visit to microgravity.
In terms of speed and duration of change, fluids are one of the most rapid. The shift
moves fluids to the upper body from the dependent (leg) portions of the body and they
collect at or above the heart. A swollen face, congested sinuses, skinny legs are obvious
signs. From a nutritional perspective the body recognizes this shift as an indication of
excess and there is a decrease in fluid intake with continued urine excretion resulting in a
net fluid loss, that is not reversed until a gravitational field is once again experienced.
After a few days a new steady state is reached in which there is a decreased blood and
extracellular volume. Intracellular volume seems to increase as there appears to be little
or no change in total body water. Most of the electrolyte loss is extracellular (2-1)
sodium over potassium. Replacing sodium dietarily provides no long-term benefit and
may actually increase calcium loss. The rapid decrease in blood volume is not a problem,
but there is no longer a residual pool of blood in the lower legs. Because of the loss of
fluid and blood volume there is an increase in the % or erythrocytes in the blood. The
increase is recognized by the body which increases red blood cell destruction and
decreases red blood cell production. This results in an increase in storage iron (ferritin) in
the body, so that less iron is needed in the diet while in space. Iron may need to be
supplemented post flight.
Calcium is mobilized from the bones and muscle mass tends to be decreased. Both of
these effects are most noticeable in the antigravity components of the body. i.e. long
bones of the leg and antigravity muscles. These changes also relate to nutritional and
dietary concerns.
In most space missions crew members have lost weight while in space that is over and
above the loss of fluids. This is due at least in part to a significant decrease in caloric
consumption. Although it is not possible to directly measure weight while in space the
problem has been effectively solved by use of the Body Mass Measuring Device
(BMMD). It has been used on the Space Shuttle and is to be incorporated into the
International Space Station to aid Astronauts in keeping track of changes in mass while
weightless in space. It reads out in kilograms and is accurate to about 0.1 kg. It functions
based on the principle that when a mass is released by a spring setting up an oscillation
the momentum of that movement is inversely proportional to the mass that is accelerated.
In this picture the handle in the left foreground is cocked putting tension on a spring,
which is then released and the BMMD calculates the periodicity of movement. If the
chair is empty the period is very rapid. The greater the mass in the chair the longer the
period of time to complete an oscillation.
Although not directly a physiological change the increase in radiation exposure while in
space is of concern. The magnitude of the problem will increase as longer missions are
planned outside of the Earth’s magnetosphere. The oxidizing radiation will increase the
need for nutritional antioxidants as a countermeasure.
NUTRITION IN SPACE
The basic goal of space nutrition is to provide a diet that is tailored to the space
environment. Historically they have had decreased percentage of fat with increased
carbohydrates. There is a tendency towards decreased fiber compared to Earth diets.
Protein content is similar.
There are a number of factors which play a role in food intake while in space. On Space
Shuttle flights the busy schedule often limits the time available to consume a regular
meal. Space motion sickness may result in loss of appetite, particularly in the first few
days of flight. Disruptions in circadian rhythms may also alter food intake. Other factors
include changed perception of taste in that food that tasted good on the ground may not be
as appetizing while in space. Repetitive food choices, with a limited selection may result
in “boredom” and result in decreased intake.
Total caloric consumption has been reduced in most space flights throughout the
program. In spite of increasing availability and planning on increased intake it has rarely
occurred. Resting metabolic rate is not changed from Earth normal while EVA results in
an increased energy output in space compared to control exercise on the ground.
Probably due to increased resistance to movement in the vacuum of space. Energy output
in space is less for exercise tasks that involve working against gravity on Earth. Total
energy expenditure has increased with increasing spaceship size and greater mobility.
There has been a consistent loss of muscle protein in American and Russian space
travelers, although the rate of loss tends to decrease on long missions. Exercise is of
some benefit but does not completely correct the deficit. These changes are in spite of
diets that provide a modest excess of protein over anticipated requirements. There is
some indication that post flight protein supplementation speeds the process of
reestablishing a preflight protein status.
The factors that affect protein loss are multiple and include inadequate energy intake and
skeletal muscle “remodeling” in microgravity. Another factor which maybe important is
generalized metabolic stress which increases protein turnover rate and decreases protein
synthesis.
Vitamin D availability may be significantly decreased in space due to the absence of
ultraviolet light activation of cutaneous precursors. Therefore diet represents essentially
the sole source of Vitamin D. On Earth the preponderance of dietary Vitamin D is from
dairy products and they currently represent a minimal component of the diet. Additional
dairy products may become available when the ISS is completed but some non-dairy
supplementation of the active form may be necessary. Alternatively the use of ultraviolet
lights could enhance Vitamin D status.
Multiple factors may be responsible for the bone calcium loss seen in space. Skeletal
unloading occurs due to both decreased muscle strength and decreased weight bearing.
Under these conditions bone resorption exceeds bone formation and there is increased
urinary calcium excretion. Currently there are no effective chemical or physical
countermeasures to bone loss.
From a nutritional perspective increased calcium in the diet may cause renal stones or the
likelihood that they will form. Conversely decreased dietary calcium may increase the
rate of body calcium loss. There is not a clear solution at this time.
Currently there is little evidence of changes needed in micronutrients because of space
flight. One potential problem could be zinc that is stored primarily in muscle and bone.
As these tissues decrease in mass there will be a concomitant decrease in zinc stores.
However, this does not appear to be a problem at this time. Iodine is added to drinking
water on the Space Shuttle and will be used on ISS; iodine toxicity would be more likely
than deficiency, but to date there are no reported occurrences of overload. There is no
evidence that B-vitamin requirements are different in space than on Earth. The potential
exists for radiation destruction of some of the B-vitamins and this could become a
problem on long term missions away from low Earth orbit.
In addition to microgravity one environmental factor that will be greatly changed while in
space is radiation. This will be particularly true for missions that move out of the
protection afforded by the Earth’s magnetosphere. Ionizing radiation will form reactive
oxygen species in the body. These oxidants can cause lipid peroxidation and thus alter
cellular membranes. Proteins can be rendered dysfunctional and DNA may have changes
that cause mutations. Dietary antioxidants represent our principle biological mechanism
for countering radiation damage. The most effective are vitamin A and beta carotene,
vitamin C (ascorbic acid) and vitamin E (the tocopherols). Several of the trace elements
also have an antioxidant effect these include copper, iron, manganese, selenium and zinc.
Although not directly associated with space radiation, the use of ionizing radiation to
sterilize foods and extend their shelf life also can destroy B-vitamins and natural
antioxidants. Radiation has been, and will continue to be, used for preserving foods for
space flight without the energy costs of freezers and refrigerators.
Pretreatment with antioxidants can reduce radiation damage, so that the availability and
use of antioxidants may be important on long term missions. One benefit of their us in
this manner is that in general they have minimal toxicity. To date there has not been an
opportunity to study the effects of space radiation on foods and antioxidants. This will
have to be accomplished prior to launching a human Mars mission.
FUTURE FOODS IN SPACE
There are several scenarios for long term human space missions that will be well beyond
Low Earth Orbit where the Space Shuttle and ISS go. One of the first will be an extended
mission to Mars that will take two and one half to three years. It is likely that most of the
food will be prepared on Earth prior to the mission and carried in storage. Such a mission
will require more shelf stable foods than are currently available. Dietary variety will be a
very important aspect of foods to be chosen for such a mission. Boredom with the
available foods will have a detrimental effect on the crews emotional well being and
interaction with their fellow crew members. A great deal of overall mission success will
depend on the physical and emotional state of the crew as they explore a new planet. This
will necessitate their consumption of sufficient nutrients to maintain a high level of body
function. In addition there is an esthetic and morale benefit in growing some vegetable
crops on the long flights. Candidate plants include lettuce, tomatoes, sprouts which
provide the value of seeing and tending the “green growing things” and providing a fresh
salad on occasion the so-called Salad Machine. Preservation and use of antioxidants will
be a necessary component to ensure crew health.
As humans move permanently to other planetary surfaces such as establishing a base or
colony on the moon or Mars, provision of a nutritious diet will become more complex. It
will no longer be possible to carry only prepared foods, instead foods must be produced
on site. This will mean that an effective Advanced Life Support facility will need to be
developed to grow foods, replenish oxygen from carbon dioxide and utilize water
transpired by the plants. This facility will be a closed loop system that is capable of
recycling carbon, hydrogen, oxygen nitrogen and water. It will grow food crops that can
sustain the colony inhabitants for an indefinite period with only minimal resupply from
Earth once it has been established. Some factors that will need to be considered in
establishing such a facility are using crops that provide a dependable yield, have a high
edible biomass yield, are of small size, will provide dietary variety and can be combined
to form a nutritionally complete diet. It may well be that some of the plants will be
genetically modified to increase levels of certain micronutrients, essential lipids or amino
acids. An additional factor is that very intensive agriculture will be practiced to grow a
maximum quantity of usable raw food in as small an area as possible.
One facet of an advanced life support system that has been given less rigorous attention
so far is the mechanisms that will be utilized to produce attractive, nutritionally complete,
varied and esthetically appetizing final dietary products from a only a few raw products.
It is likely that the major raw products will include wheat, rice, soybeans and perhaps
sweet and white potatoes and peanuts. These would be the major crops that would need
to be processed in order to be used. Complex processing is particularly necessary for the
cereal grains and soybeans. Some considerations for such a food processing facility will
be to use crops that can be easily processed into numerous edible products. One
additional aspect of the overall facility will be to effectively utilize the cellulose and
lignin that are not digestible by humans. There are a number of single cell organisms that
can break down these polymers, but algae and yeast are not esthetically attractive as
significant components of our diets. It is likely that there will be heavy reliance on
prepackaged spices, flavors. antioxidants and trace nutrients that will be sent at intervals
to the colony from Earth.
BIOGRAPHY
Robert W. Phillips (Bob) DVM, Ph.D. received a BS degree in animal nutrition, followed
by a Doctorate in Veterinary Medicine at Colorado State University. He subsequently
received a Ph.D. in Physiology/Nutrition at the University of California. Following that
degree he was active on the faculty of the Department of Physiology at Colorado State
University for over 20 years teaching and conducting research focused in metabolism and
nutrition.
In 1984 he joined NASA as a Payload Specialist training for the Space Shuttle flight
Space Laboratory Life Sciences 1, (STS 40) which ultimately launched in June of 1991.
Shortly before that mission he was removed from flight status by flight medicine and
served as alternate Payload Specialist for the mission at the Payload Operations Control
Center. Following that shuttle flight he spent three years at NASA Headquarters in
Washington DC, principally as Space Station Chief Scientist. He is currently working in
Outreach and Education, part time, for NASA Life Sciences through a Cooperative
Agreement with Colorado State University.
Bob is a Professor Emeritus in the Department of Physiology at Colorado State
University and an emeritus member of the American Institute of Nutrition and the
American Physiological Society. He is a charter Diplomate of the American College of
Veterinary Nutrition and a Distinguished Scholar of the National Academy of Practices.
REFERENCES FOR FURTHER READING
Nutrition in Spaceflight and Weightless Models. Lane, H. W. and Schoeller, D. A. Ed.
1999, CRC Press, Boca Raton, Florida.
Food and Nutrition During Spaceflight. Phillips, R. W. In Fundamentals of Space Life
Sciences, Churchill, S. E. Ed. 1997, Krieger Publishing Co. Malabar Florida.