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Space nutrition: the key role of

nutrition in human space flight

Catalano Enrico1

1Consorzio Interuniversitario Nazionale per la

Scienza e Tecnologia dei Materiali (INSTM),

Via Giuseppe Giusti, 9, 50121 Firenze (FI),

Italy. e-mail: enrico.catalano@med.uniupo.it

Corresponding author

Catalano Enrico

Consorzio Interuniversitario Nazionale per la

Scienza e Tecnologia dei Materiali (INSTM),

Via Giuseppe Giusti, 9, 50121 Firenze (FI),

Italy. e-mail: enrico.catalano@med.uniupo.it

Abstract

From the basic impact of nutrient intake on

health maintenance to the psychosocial

benefits of mealtime, great advancements in

nutritional sciences for support of human

space travel have occurred over the past 50

years. Nutrition in space has many areas of

impact, including provision of required

nutrients and maintenance of endocrine,

immune, and musculoskeletal systems. It is

affected by environmental conditions such as

radiation, temperature, and atmospheric

pressures, and these are reviewed. Nutrition

with respect to space flight is closely

interconnected with other life sciences

research disciplines including the study of

hematology, immunology, as well as

neurosensory, cardiovascular, gastrointestinal,

circadian rhythms, and musculoskeletal

physiology. Psychosocial aspects

of nutrition are also important for more

productive missions and crew morale.

Research conducted to determine the impact

of spaceflight on human physiology and

subsequent nutritional requirements will also

have direct and indirect applications in Earth-

based nutrition research. Cumulative

nutritional research over the past five decades

has resulted in the current nutritional

requirements for astronauts. Realization of the

full role of nutrition during spaceflight is

critical for the success of extended-duration

missions. Long-duration missions will require

quantitation of nutrient requirements for

maintenance of health and protection against

the effects of microgravity.

Keywords: Space nutrition, space flight,

effects of microgravity, astronauts, space food

1. Introduction

Nutrition has played a critical role throughout

the history of exploration, and space

exploration is no exception. The purpose of

this article is to review our current knowledge

of space flight nutrition and food science.

Humans have adapted well to space flight,

and over the past 50 years, we have

substantially increased our understanding of

the various physiologic changes that occur

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during and after space flight [1]. Nutrition in

space has many aspects of impact, including

provision of required nutrients and

maintenance of endocrine, immune, and

musculoskeletal systems. However, the

underlying mechanisms for many of these

alterations remain unclear. This article

describes prior and ongoing nutritional

research undertaken with the goal of assuring

human health and survival during space flight.

Nutrition and food science research overlap

with or are integral to many other aspects of

space medicine and physiology including

psychological health, sleep and circadian

rhythmicity, taste and odor sensitivities,

radiation exposure, body fluid shifts, and

wound healing and to changes in the

musculoskeletal, neurosensory,

gastrointestinal, hematologic, and

immunologic systems. Nutrient intake play a

fundamental role from health maintenance to

the psychosocial benefits of mealtime, the

role of nutrition in space is evident. Recent

advances in genomics and proteomics are just

beginning to be applied in space biomedical

research, and it is likely that findings from

such studies will be applicable to applied

human nutritional science.

Long-duration missions will require the right

amount of nutrient requirements for

maintenance of health and protection against

the effects of microgravity. Psychosocial

aspects of nutrition will also be important for

more productive missions and crew morale.

Realization of the full role of nutrition during

spaceflight is critical for the success of

extended-duration missions. Research

conducted to determine the impact of

spaceflight on human physiology and

subsequent nutritional requirements will also

have direct and indirect applications in Earth-

based nutrition research.

Understanding the nutritional requirements of

space travelers and the role of nutrition in

human adaptation to microgravity are as

critical to crew safety and mission success as

any of the mechanical systems of the

spacecraft itself. There are many facets to

nutrition and health on Earth. Space flight

introduces further complications, and many

gaps remain in our knowledge of the

relationships between nutrition and health in

space that need to be filled before we can

safely embark on “exploration” missions, that

is, missions beyond low Earth orbit. At the

surface of these unknowns is the need to

understand and define basic nutrient

requirements during extended stays in

microgravity. Beyond this lies the need to

characterize the role of nutrition in the

adaptation of physiological systems to

microgravity, and/or the impact of these

changes on nutrition. Additionally,

environmental impacts (including radiation,

and spacecraft and spacesuit atmospheres) can

alter nutritional status and nutritional

requirements of space flight. For surface

missions (on, for example, the moon and

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Mars), partial gravity may complicate the

situation further. Finally, many potential

targets for nutritional countermeasures exist,

where modified dietary intake may help to

counteract or mitigate some of the negative

effects of space flight on the human body.

The US space life sciences research

community has developed a set of critical

questions and a road map to clearly

emphasize research efforts that ultimately will

reduce to humans the risk associated with

space travel and habitation [2]. Relevant

research has been conducted in space and on

the ground using animal models and human

ground-based analogs [3]. Throughout the

five-decade history of human space flight,

nutrition and food research have been an

integral component of various missions.

2. Astronaut nutrition

Spacecraft, the space environment, and

weightlessness itself all impact human

physiology. Clean air, drinkable water, and

effective waste collection systems are

required for maintaining a habitable

environment. Adequate energy intake is

perhaps the single most important aspect of

astronaut nutrition [4]. This is not only

because energy in and of itself is more

important than other nutritional factors, but

also because if enough food is consumed to

meet energy needs, then generally other

nutrients will also be consumed in reasonable

amounts. Weightlessness impacts almost

every system in the body, including those of

the bones, muscles, heart and blood vessels,

and nerves. There are many facets to

maintaining eucaloric intake during space

flight, including energy requirements;

physiological changes in taste and satiety;

scheduling issues of allotting time for meal

preparation, consumption, and cleanup; food

quality; and even food availability [4]. Little

research has been done on differences in fuel

components (protein, carbohydrate, fat)

during space flight, or on cofactors (eg,

vitamins) of energy utilization. We review

these here, highlighting what has been done

and potential areas of future research.

2.1 Space food

Space food is a variety of food products,

specially created and processed for

consumption by astronauts in outer space. The

food has specific requirements of providing

balanced nutrition for individuals working in

space, while being easy and safe to store,

prepare and consume in the machinery-filled

low gravity environments of manned

spacecraft [1]. In recent years, space food has

been used by various nations engaging on

space programs as a way to share and show

off their cultural identity and facilitate

intercultural communication. Although

astronauts consume a wide variety of foods

and beverages in space, the initial idea was to

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supply astronauts with a formula diet that

would supply all the needed vitamins and

nutrients [2]. With the long-duration missions

aboard the International Space Station (ISS),

it has become clear that more emphasis needs

to be placed on improving human habitability.

In fact, in the last years a new project: “The

Vegetable Production System” (VEGGIE)

was developed to provide a means to supply

crews with a continuous source of fresh food

and a tool for relaxation and recreation. The

Veggie provides lighting and nutrient

delivery, but utilizes the cabin environment

for temperature control and as a source of

carbon dioxide to promote growth [64].

The Vegetable Production System (Veggie) is

a deployable plant growth unit capable of

producing salad-type crops to provide the

crew with a palatable, nutritious, and safe

source of fresh food and a tool to support

relaxation and recreation. During 2015 red

romaine lettuce was cultivated and consumed

on board on ISS by the crew members [65].

Veggie will remain on the station

permanently and could become a research

platform for other top-growing plant

experiments.

3. Bone and nutrition in space

Bone is a living tissue, and is constantly being

remodeled. This remodeling is achieved

through breakdown of existing bone tissue (a

process called resorption) and formation of

new bone tissue. Chemicals in the blood and

urine can be measured to determine the

relative amounts of bone resorption and

formation. During spaceflight, bone

resorption increases significantly, and

formation either remains unchanged or

decreases slightly [5]. The net effect of this

imbalance is a loss of bone mass. Bone loss,

especially in the legs, is increased during

spaceflight. This is most important on flights

longer than thirty days, because the amount of

bone lost increases as the length of time in

space increases. Weightlessness also increases

excretion of calcium in the urine and the risk

of forming kidney stones. Both of these

conditions are related to bone loss [5].

Calcium and bone metabolism remain key

concerns for space travelers, and ground-

based models of space flight have provided a

vast literature to complement the smaller set

of reports from flight studies. Increased bone

resorption and largely unchanged bone

formation result in the loss of calcium and

bone mineral during space flight, which alters

the endocrine regulation of calcium

metabolism [6]. Physical, pharmacologic, and

nutritional means have been used to

counteract these changes. In 2012, heavy

resistance exercise plus good nutritional and

vitamin D status were demonstrated to reduce

loss of bone mineral density on long-duration

International Space Station missions [6].

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Uncertainty continues to exist, however, as to

whether the bone is as strong after flight as it

was before flight and whether nutritional and

exercise prescriptions can be optimized

during space flight. Findings from these

studies not only will help future space

explorers but also will broaden our

understanding of the regulation of bone and

calcium homeostasis on Earth.

Whereas nutrition is critical for virtually all

systems, the interaction of nutrition with bone

is perhaps more extensive and complex than

most of its interactions with body systems.

Many nutrients are important for healthy

bone, particularly calcium and vitamin D.

When a food containing calcium is eaten, the

calcium is absorbed by the intestines and goes

into the bloodstream. Absorption of calcium

from the intestines decreases during

spaceflight. Even when astronauts take extra

calcium as a supplement, they still lose bone

[7].

Bone is the body’s reservoir of calcium,

which provides structure and strength to bone,

but also provides a ready resource to maintain

blood calcium levels during periods with

insufficient dietary provision of calcium.

Several nutrients are required for the

synthesis of bone, including protein and

vitamins D, K, and C. On Earth, the body can

produce vitamin D after the skin is exposed to

the sun's ultraviolet light. In space, astronauts

could receive too much ultraviolet light, so

spacecraft are shielded to prevent this

exposure. Because of this, all of the

astronauts' vitamin D has to be provided by

their diet. However, it is very common for

vitamin D levels to decrease during

spaceflight [7].

Multiple risks are associated with bone loss

during space flight. Almost immediately upon

entering weightlessness, bone resorption

increases, and calcium (and other minerals)

are released into the blood and urine. This

increases kidney stone risk on short missions,

and on longer missions, chronic bone and

calcium loss can increase risks to bone health

both in the near term (eg, risk of fractures)

and in the long term (eg, risk of osteoporosis-

like bone degradation).

Sodium intake is also a concern during

spaceflight, because space diets tend to have

relatively high amounts of sodium. Increased

dietary sodium is associated with increased

amounts of calcium in the urine and may

relate to the increased risk of kidney stones.

The potential effect of these and other

nutrients on the maintenance of bone health

during spaceflight highlights the importance

of optimal dietary intake. The changes in

bone during spaceflight are very similar to

those seen in certain situations on the ground

[7]. There are similarities to osteoporosis, and

even paralysis. While osteoporosis has many

causes, the end result seems to be similar to

spaceflight bone loss. Paralyzed individuals

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have biochemical changes very similar to

those of astronauts. This is because in both

cases the bones are not being used for

support. In fact, one of the ways spaceflight

bone loss is studied is to have people lie in

bed for several weeks. Using this approach,

scientists attempt to understand the

mechanisms of bone loss and to test ways to

counteract it. If they can find ways to

successfully counteract spaceflight bone loss,

doctors may be able to use similar methods to

treat people with osteoporosis or paralysis. It

is not clear whether bone mass lost in space is

fully replaced after returning to Earth. It is

also unclear whether the quality (or strength)

of the replaced bone is the same as the bone

that was there before a spaceflight.

Preliminary data seem to show that some

crew members do indeed regain their preflight

bone mass, but this process takes about two or

three times as long as their flight. The ability

to understand and counteract weightlessness-

induced bone loss remains a critical issue for

astronaut health and safety. The International

Space Station provides the opportunity for

monitoring the effects of space flight on bone

physiology to be documented, along with the

testing of countermeasures aimed at

counteracting bone loss [8].

4. Muscle loss in microgravity conditions

Loss of body weight (mass) is a consistent

finding throughout the history of spaceflight.

Typically, these losses are small (1 percent to

5 percent of body mass), but they can reach

10 percent to 15 percent of preflight body

mass. Although a 1 percent body-weight loss

can be explained by loss of body water, most

of the observed loss of body weight is

accounted for by loss of muscle and adipose

(fat) tissue. Exposure to microgravity reduces

muscle mass, volume, and performance,

especially in the legs, on both short and long

flights [9-11].

Weightlessness leads to loss of muscle mass

and muscle volume, weakening muscle

performance, especially in the legs. The loss

is believed to be related to a metabolic stress

associated with spaceflight. These findings

are similar to those found in patients with

serious diseases or trauma, such as burn

patients.

The primary countermeasure against muscle

loss remains adequate energy intake, which

will no doubt include protein, but protein

supplements are not required. Use of protein

and amino acid supplementation has long

been studied as a potential means to mitigate

muscle loss associated with space flight, but

results have been inconclusive at best [12,

13].

It remains unclear whether nutritional

measures beyond the consumption of

adequate energy and protein would be

beneficial in reducing muscle atrophy [14].

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Exercise routines have not succeeded in

maintaining muscle mass or strength of

astronauts during spaceflight. Most of the

exercises performed have been aerobic (e.g.,

treadmill, stationary bicycle). Use of

resistance exercise, in which a weight (or

another person) provides resistance to

exercise against, has been proposed to aid in

the maintenance of both muscle and bone

during flight. Ground-based studies (not done

in space) of resistance exercise show that it

may be helpful, not only for muscle but also

for bone [8]. Studies being conducted on the

International Space Station are testing the

effectiveness of this type of exercise for

astronauts.

Exercise is the most common first-pass

approach to maintaining muscle mass and

strength [15]. The exercise regimens tested as

countermeasures to date have generally not

succeeded in maintaining muscle mass or

strength (or bone mass) during space flight

[15-17]. Many types of exercise protocols

have been proposed to aid in the maintenance

of both muscle and bone during flight, but

these have yet to be fully tested on orbit [18,

19].

5. Endocrine system function related to the

nutritional status in the space flight

The endocrine system appears to be sensitive

to the conditions of space flight. Several

hormones may increase in the circulation as

part of the stress response to microgravity

conditions, including epinephrine and

norepinephrine, adrenocorticotropin, cortisol.

These hormones play a role in the elevation of

plasma glucose and fatty acids, in increased

lipolytic activity in adipose tissue, in reducing

lipogenesis and in raising glycogen content in

the liver [20]. These hormones have been

measured during and after space flight: data

from previous space missions show increases

in catabolic hormones (cortisol, glucagone)

and a prolonged elevation of 3-

methylhistidine excretion, suggesting a

chronic metabolic stress response that may be

influenced not only by mission length but also

by energy intake, exercise regimen and even

gender [21]. Such changes may indeed be

involved in promoting muscle and bone loss,

in impairing immune status, in the regulation

of body fluids and electrolytes that affects the

cardiovascular response to microgravity.

Catecholamines as well as renin-aldosterone

are also involved in fluid balance, being part

of sodium-retaining endocrine systems;

consistent observations in various missions

(Mir 97, Spacelab mission D-2, Euromir 94)

revealed an elevated activity that may lead to

sodium storage without an accompanying

fluid retention [22]. This may be part of the

reason leading to an extravasation of fluid

after an increase in vascular permeability. An

enormous capacity for sodium in the extra-

vascular space and a mechanism that allows

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the dissociation between water and sodium

handling may contribute to fluid balance

adaptation in weightlessness [23].

6. Gastrointestinal function during space

missions

Astronauts experience gastrointestinal

changes early in flight, gaseous stomach

occurs due to the inability of gases to rise.

Furthermore the effects of micro-gravity are

presumed to alter the contact of the gastric

contents with the gastrointestinal mucus.

However, cephalic fluid shifts, in combination

with commonly observed dehydration, could

possibly affect gastrointestinal motility

through reduced splanchnic flow. The effect

of chronic inactivity increases transit time and

potentially changes gastrointestinal microflora

[24]. Gastrointestinal integrity and bacterial

balance may be improved by probiotics and

prebiotics that should be studied for a possible

inclusion in space foods. Probiotics, defined

as microbial food supplements that

beneficially affect the host improving its

intestinal microbial balance, have been

studied to change the composition of colonic

microbiota by increasing bacterial groups

such as Bifidobacteria and Lactobacilli that

are perceived as exerting health-promoting

properties. However, these changes may be

transient, and the implantation of exogenous

bacteria becomes limited. On the other hand,

since astronauts do have an impaired immune

function, as discussed in the next section,

differences in the immunomodulatory effects

of candidate probiotic bacteria should be

taken into consideration and the positive

effect should be studied in weightlessness

models. The use of prebiotics partly

overcomes the limitations of probiotics.

Prebiotics are growth substrates and not

viable entities, specifically directed toward

potentially beneficial bacteria already

growing in the colon [25].

7. Cardiovascular health and nutrition in

space

Cardiovascular issues are a key concern for

space travelers, but the role of nutrition in

cardiovascular adaptation has not yet been

well characterized [26-28]. It is worth noting

that multiple studies are being planned or are

underway on ISS to shed light on this area in

the near future. Omega-3 fatty acids have a

clear beneficial impact on cardiovascular

health on Earth, but such effects have not

been evaluated during space flight [29].

Nonetheless, the initial efforts being made to

increase fish and omega-3 fatty acid intake in

astronauts for the benefit of other systems

(bone, muscle) will likely have positive

effects here as well [29].

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8. Iron metabolism during space flight

Space flight- induced hematologic changes

have been observed since the initial days of

space exploration. Space flight anemia is a

widely recognized phenomenon in astronauts.

The implications of hematologic changes for

long-term space flight may have

consequences on the health of astronauts [30].

Reduction in circulating red blood cells and

plasma volume results in a 10% to 15%

decrement in circulatory volume. This effect

appears to be a normal physiologic adaptation

to weightlessness and results from the

removal of newly released blood cells from

the circulation [30]. Iron availability

increases, and (in the few subjects studied)

iron stores increase during long-duration

space flight. The consequences of these

changes are not fully understood.

9. Oxidative stress and space flight

Space flight is associated with an increase in

oxidative stress and to significantly high

radiation, even with considerable shielding on

the spacecraft. In the human body, solar

radiation or low wavelength electromagnetic

radiation (such as gamma rays) from the earth

or space environment can split water to

generate reactive free radicals. These reactive

free radicals can react in the body leading to

oxidative damage to lipids, proteins and

DNA. Recent data on the oxidant damage

have underlined its increase post-flight

probably due to a combination of augmented

metabolic activity and loss of some host

antioxidant defences in-flight [31, 32].

The effect is more pronounced after long-

duration space flight. The effects last for

several weeks after landing. In humans there

is increased lipid peroxidation in erythrocyte

membranes, reduction in some blood

antioxidants, and increased urinary excretion

of markers for oxidative damage to lipids and

DNA, respectively: 8- iso-prostaglandin F2α

and 8-oxo-7,8 dihydro-2 deoxyguanosine [31,

33].

Decreasing the imbalance between the

production of endogenous oxidant defenses

and oxidant production by increasing the

supply of dietary antioxidants may lessen the

severity of the postflight increase in oxidative

stress. The antioxidant defence system can be

implemented to counteract oxidative stress by

supplementing vitamins in dietary intake of

astronauts such as tocopherols and

tocotrienols (vitamin E), ascorbate (vitamin

C), vitamin A and its precursors betacarotene

and other carotenoids, trace elements and

minerals such as copper, manganese, zinc,

selenium and iron [34]. Actual

recommendations of vitamin C intake have

been raised from 60 to 100 mg per day,

during space flights [4, 35]. Dietary and

antioxidant defences appear to play a

protective role in muscle cells by reducing

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associated oxidative damage to lipids, nucleic

acids, and proteins [34]. However, iron

supplementation in microgravity is not

recommended because the reduction in red

cell mass and the consequent increase in iron

stores could augment free radical generation.

Dietary intake and/or supplementation of

particular nutrients showed also an important

prophylactic role against photo-oxidative

damage to cell membranes [36]. Nutritional

countermeasures in space with antioxidant

supplementation provide a great opportunity

for research within space flight models,

whereas the main concern is to counteract the

potential for long-term oxidative damage in

humans under these conditions.

10. Ophthalmic changes in space flight

Microgravity is the dominant cause of many

physiological changes during spaceflight and

is thought to contribute significantly to the

observed ophthalmic changes. Ophthalmic

health among astronauts has gotten attention

in recent years because of a newly identified

issue for some crewmembers. In addition to a

general increase in cataract risk, some

crewmembers have experienced vision-related

changes after long-duration space flight [37,

38].

It has recently been recognized that vision

changes are actually quite common in

astronauts and are associated with a

constellation of findings including elevated

intracranial pressure, optic disc edema, globe

flattening, optic nerve sheath thickening,

hyperopic shifts, choroidal folds, cotton wool

spots and retinal changes [39]. The etiology

of the refractive and structural ophthalmic

changes is currently not known and continues

to be researched, but biochemical evidence

indicates that the folate- and vitamin B12-

dependent 1-carbon transfer pathway may be

involved. Nutrition is known to be an

important factor for ophthalmic health in

general.

11. Immune changes in space flight

Optimal function of the immune system is

impaired in the presence of malnutrition.

Without adequate nutrition, the immune

system is clearly deprived of the components

needed to generate an effective immune

response [40, 41]. Nutrients act as

antioxidants and as cofactors [42]. Exposure

of animals and humans to space flight

conditions has resulted in numerous

alterations in immunological parameters, for

instance, decreases in blast transformation of

lymphocytes, cytokine production, and

natural killer cell activity. After flight,

alterations in leukocyte subset distribution

have also been reported for humans and

animals [43]. Disruption of nutritional

balance and dietary intake of astronauts and

cosmonauts during space flight, which is

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often accompanied by a stress response, might

influence their immune response [44, 45].

Findings of energy deficiency on long

duration missions increase susceptibility to

infections [46]. Studies on cosmonauts during

space flight have shown that IgG levels were

unchanged, whereas IgA and IgM levels were

sometimes increased [47]. A decreased

cytotoxicity in cosmonauts after space flight

can be proposed, and this includes the

defective function of NK cells and the

reduced number of circulating effector cells

[48]. Physical and psychological stress

associated with space flight resulted in

decreased virus-specific T-cell immunity and

reactivation of EBV [49]; almost certainly

immunity changes in space are similar to

those occurring during acute stress conditions.

Therefore, it is reasonable to consider stress-

related immunotherapy approaches in the

practice of space medicine mainly because

concerns have been raised about the possible

risks of post- flight infections. A decrease in

the number of T- lymphocytes and impairment

of their function is an important effect of

weightlessness on the immune system. From a

nutritional point of view, we have to consider

that deficiency of zinc is associated with

similar changes in T-lymphocytes.

Suggestions that modifications to the diet may

have a beneficial effect on health are not new.

It is well known from ground research that a

lack of macronutrients or selected

micronutrients, like zinc, selenium, and the

antioxidant vitamins, can have profound

effects on immune function [50-52]. Such a

lack of nutrients also leads to deregulation of

the balanced host response [53]. In fact,

several micronutrients such as vitamin A,

beta-carotene, folic acid, vitamin B12,

vitamin C, riboflavin, iron, selenium, zinc

have immunomodulating actions [54, 55].

Recent work demonstrates that some nutrients

such as arginine, glutamine, nucleotides and

omega-3 fatty acids may affect immune

function [56]. The dietetic intake of these

nutrients should be considered in order to

recommend appropriate nutritional

supplementation aimed at reducing immune

changes due to sub-optimal nutrition that may

eventually have negative consequences on

immune status and susceptibility to a variety

of pathogens. Detailed information on the

effects of many micronutrients during space

flight are mandatory before specific

nutritional recommendations can be made,

especially with respect to their relationship

with immune system function.

Moreover, the latest data (from healthy

subjects and patients with inflammatory

diseases) show that probiotics can be used as

innovative tools to improve the intestine’s

immunologic barrier and produce a gut-

stabilizing effect. Many of the probiotic

effects are mediated via immune regulation,

in particular by control of the balance of

proinflammatory and antiinflammatory

cytokines [57]. Recent results demonstrate

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that dietary consumption of specific

probiotics can enhance natural immunity in

healthy elderly subjects [58]. This evidence

suggests that the consumption of cultures of

beneficial live microorganisms that act as

probiotics should be evaluated in target

specific populations, including astronauts.

12. Discussion

Adequate nutrition is critical for maintenance

of crew health during and after extended-

duration space flight. Provision of a variety of

available foods [59] with positive sensory

characteristics [60], and adequate time for

preparation and consumption of meals

enhances food intake by the crew members.

The observed changes in food intake,

hypothalamic monoamines, and peripheral

hormones suggest that besides microgravity,

continuous light exposure contributes to the

observed anorexia, and its metabolic sequelae

including bone loss [61]. Poor or inadequate

sleep may affect eating and drinking behavior,

thus, generating the potential for nutritional

problems.

The impact of weightlessness on human

physiology is profound, with effects on many

systems related to nutrition, including bone,

muscle, hematology, fluid and electrolyte

regulation. Additionally, we have much to

learn regarding the impact of weightlessness

on absorption, metabolism, and excretion of

nutrients, and this will ultimately determine

the nutrient requirements for extended-

duration space flight. Existing nutritional

requirements for extended-duration space

flight have been formulated based on limited

flight research, and extrapolation from

ground-based research. In this regard,

NASA’s Nutritional Biochemistry Laboratory

was charged with defining the nutritional

requirements for space flight. This is

accomplished through both operational and

research projects. A nutritional status

assessment program is included operationally

for all International Space Station astronauts.

This medical requirement includes

biochemical and dietary assessments, and is

completed before, during, and after the

missions. This program will provide

information about crew health and nutritional

status, and will also provide assessments of

countermeasure efficacy.

Although experience with long-term space

flight has provided considerable confidence in

the ability of the human body to recover from

space flight and readapt to the Earth

environment, effects observed on the long

Skylab, Mir, and NASA-Mir missions have

convinced flight physicians and scientists that

countermeasures and monitoring are essential

to the success of long duration spaceflight.

Countermeasures are methods used to limit

the negative physical and psychological

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effects of the space environment on humans.

Nutrition and foods are essential for

maintenance of health and for enabling certain

countermeasures such as exercise. Critical

questions and a road map point to the

important areas of nutrition and food science

research needed in the future. These include

development and use of genomic and

proteomic research and development and use

of other advanced technologies. There must

be interactions between the various

disciplines to determine the underlying

mechanisms and to apply them to nutritional

requirements to ensure a healthy and

productive crew. However, due to limitations

of spaceflight research opportunities, ground-

based models are essential for understanding

nutrition-related physiologic changes and

their underlying mechanisms. Nutrition

research efforts require a wide range of

models and interdisciplinary approaches

including contributions from physiology,

biochemistry, psychology, food science and

technology, horticulture, and advanced

medical technologies.

13. Conclusions

After 55 years of human spaceflight from the

first human Yuri Gagarin to journey into outer

space and a great deal of space life sciences

research, much has been learned about human

adaptation to microgravity exposure.

NASA has an exciting new vision of future

spaceflight to favour the return of humans to

the moon in preparation for visits to Mars and

possibly beyond. Moon missions are essential

to the exploration of more distant worlds.

Extended lunar stays build the experience and

expertise needed for the long-term space

missions required to visit other planets.

Moreover NASA is working toward sending

astronauts to a near-Earth asteroid by 2025,

then on to the vicinity of the Red Planet by

the mid-2030s. Part of this preparation

involves studying the psychological and

physiological effects of long-term spaceflight,

which the agency investigated during 2015 on

one-year missions to the International Space

Station (The standard stay for astronauts

aboard the orbiting lab has been six months).

The biggest challenge to human exploration

of deep-space destinations is related to high

radiation levels beyond Earth orbit. With

current spacecraft technology, astronauts can

cruise through deep space for a maximum of

one year or so before accumulating a

dangerously high radiation dose, researchers

say. As a result, many intriguing solar system

targets remain off- limits to human exploration

at the moment. A one-year spaceflight cap

would still allow manned missions to some

intriguing destinations, such as Mars.

For future long-term mission replacement of

gravity by centrifugation (“artificial gravity”)

has been proposed as a multi-system

14

countermeasure [102, 103], but particularly

for bone. Although some initial studies have

been completed, the optimal artificial gravity

prescription for bone, including dose,

duration, and frequency of centrifugation,

remains to be identified [82, 104], along with

its potential impact on nutrition and related

systems [105, 106].

In fact, data gathered by NASA’s Curiosity

rover suggest that astronauts could endure a

six-month outbound flight, a 600-day stay on

the Martian surface and the six-month journey

home without accumulating a worryingly high

radiation dose.

Mars missions will require additional

technological and biomedical advances.

Current scenarios, based on existing

propulsion technology, are for missions of

about 1-1.5 years, with 6 months of transit to

Mars, 2-6 month stay on the Mars surface and

another 6‐month voyage to return. On these

flights, early return will not be possible, and

thus in situ medical capabilities are needed.

Determining what diagnostic testing is

required and developing technologies to allow

such testing in microgravity or 1/3‐gravity

will be challenging, to say the least.

It can be realistically predicted that nutritional

balance and dietary adequacy will become

increasingly important on future long-term

space flights especially regarding future

missions to the International Space Station

and to Mars.

From a nutrition perspective, critical

questions remain regarding the nutrient

requirements for extended‐duration missions

and the ability of nutrients to serve as

countermeasures to mitigate some of the

negative effects of spaceflight. Nutrition is an

essential part of maintaining the endocrine

and immune system, skeletal and muscle

integrity, and the hydration status of the space

crew, all of which are important for extended-

duration missions and in those where

strenuous extravehicular activities are

required. In addition, the psychological

aspects of individuals during space flights

underline the role of the mealtime perceived

as a welcome break from job-related activities

as well as a chance to socialize.

Initial studies are underway to better

understand nutritional requirements in

microgravity, the stability of nutrients in

foods stored in space, and oxidative damage

and how to counteract it. Moreover the design

of future space suits is currently underway,

and one of the considerations is expanding the

ability to provide nutrition during

extravehicular activity, either by making a

nutritional beverage available in the suit or by

making it possible for an astronaut to easily

exit the suit for a snack or lunch.

From a food perspective, storage of foods for

up to 5 years will be required (as much of the

food as possible will be sent ahead of the

crewed mission), and ensuring adequate

nutrient content at the time of consumption

15

will be critical. For astronauts depending for

months to years on a closed food system, any

nutrient deficiency or excess could be

catastrophic.

Diet will be important for the efficacy of the

countermeasures and prevention of

compounding problems. Further efforts will

be implemented to ameliorate dietary

adequacy and food safety in order to

counteract deleterious physiological changes,

psychosocial repercussions and

microbiological hazards. Finally, all space

food systems will be designed to meet not

only individual nutritional requirements but

also different food preferences and eating

habits, according to the different cultural

background and country of origin of the crew

members.

The question of in situ production of food

based on crops will be the solution and the

additional value to provide a set of nutrients

for crew members. Vitamins A, B12, C, D, E,

K, etc. as well as mineral salts could be used

in future as countermeasures for the radiation

exposure of deep space during long‐duration

space missions. Genetically modified foods

could also be the key to solve sudden

nutritional problems during long-term

missions. Nutrition will be the key-factor for

the next phases of exploration beyond this

planet, and space nutrition will ensure optimal

health and mission success.

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