Throughout human history, nutrient and nutrition have been fundamental determinants in the success—or failure—of exploration missions. The National Aeronautics and Space Administration (NASA) is planning missions that will put the first adult female and side by side man on the moon this decade and will transport humans to Mars adjacent decade. Greater propulsion capability is needed to supply missions equally distance from Earth increases and planetary physics makes regular resupply unfeasible. Hence, providing food and nutrition becomes a significant challenge.

The 20th anniversary of continuous human presence on the International Infinite Station (ISS) is approaching. NASA has provided a safe food system for astronauts on 4- to 11-mo missions in low-Globe orbit. Nonetheless, express water, storage, crew time, and nutrient preparation capability (due east.yard., add water, rut) restrict the crew to a limited choice of shelf-stable, single-serving nutrient products either in their natural form or preserved by dehydration, antiphon thermostabilization, or irradiation. Astronauts select ∼xx% of their nutrient items and beverages, whereas ∼80% of their nutrition comes from a shared, standard ready of foods. Resupply vehicles get in several times a year, bringing some fresh fruits and vegetables and some semi-shelf-stable specialty items. Astronauts report that these deliveries provide profound psychological benefits. The degree to which these intermittent deliveries stave off nutritional deficiencies is not easy to quantify because the variety and amount of fresh fruit and vegetables vary, and they are shelf-life express to a few days or weeks.

Although Apollo astronauts reported hot water to be "essential and non-negotiable" on ∼10-d lunar missions (1), resource constraints on upcoming lunar missions may prevent hot h2o or a nutrient warmer for at least part of the mission. Food mass and volume will be highly constrained, despite frequent and intense lunar walks increasing free energy expenditure and limiting available time to consume. Concerns ascend every bit to whether a limited diet of common cold foods for up to 8 d will affect intake, performance, and morale and if these may risk accomplishing mission objectives. Requests to reduce the mass of the lunar food system by ∼x% led to "repast replacement bars" intended to replace the calories and nutrients of a repast (∼750 kcal). One test of these bars in a thirty-d closed-chamber study found reduced food intake and behavioral implications in high-performing individuals (2).

Developing a food system for Mars missions will exist tremendously more challenging than for lunar or ISS missions. A likely Mars mission has crews spending six mo speeding away from their home planet: a journey analogous to an ISS trip just without the occasional deliveries of fresh foods. This journey ends with the coiffure spending 18 mo on the surface of Mars with no possibility of resupply or emergency return, and then the crew will embark on a 6-mo render journeying to Earth. The psychological touch on of watching Earth become smaller and communication with World taking longer is daunting, as are the furnishings of radiations, microgravity, isolation, and confinement (3). Nutrient is the one countermeasure to physiological and behavioral decrements that we know volition be on lath—the question is, tin we optimize the nutrient system to mitigate negative consequences of the space surroundings while minimizing resource utilization and maintaining food palatability throughout the mission? Although many food systems exist on Earth, the ability of these to run across spaceflight demands has not yet been established, and their feasibility within cost and schedule limits remains unclear.

Although oftentimes considered a secondary issue to get to Mars, nosotros highlight here the all-encompassing challenges of developing a nutrient system for space exploration. Even if the rocket and engineering systems work perfectly, if the food organization fails to meet whatever of these criteria, the journey will have the same epilogue every bit many other expeditions that never even left the domicile planet only went horribly wrong solely because of food and nutrition organization failures. Historic polar expeditions were devastated by bereft (thiamine and vitamin C) or excessive amounts of vitamins or minerals (vitamin A and pb) in the nutrition (4, 5), some of which were directly related to advances in food preservation at the time (6).

In short, and as highlighted inEffigy 1, any infinite nutrient organisation must meet bones criteria:

  • Safety. It is paramount that we understand and minimize whatsoever nutrient-associated chance to astronaut wellness and to the vehicle. The ISS food system undergoes all-encompassing basis processing and testing to minimize the chance of nutrient poisoning. Foods grown in the spacecraft will have microbiological testing and cleaning requirements, as well as innovate waste product streams into the habitat air, water, and waste matter systems. Current microbiological and nutritional analyses require substantial resource and waste product-processing capacity that will not transfer as is to the resources-restricted spacecraft.

  • Stability. Current designs for Mars missions require nutrient system stability (and/or ingredients and equipment) through at least 5 y of storage. While the utilize of refrigerators and freezers is possible, inclusion of this equipment volition accept to be considered against mission book, mass, and power constraints. No food system to engagement has been devised or tested or has demonstrated it can provide adequate acceptability and nutrition for 5 y, allow alone one that besides meets the restricted mass, volume, and storage in the hostile spaceflight environment (e.g., radiation exposure, temperature extremes).

  • Palatability. A food system could meet all requisite criteria, but if it is not palatable, information technology will non be consumed in adequate amounts to back up health, functioning, and morale. A common misperception is that high-performing individuals, such as astronauts, will swallow whatsoever is required to successfully consummate a mission. The astronauts must be willing and able to prepare and consume the foods available for the duration of whatsoever mission, and familiar and acceptable food becomes even more of import as duration, altitude, and isolation increase. Like Earth-jump humans, astronauts crave enjoyable foods that the boilerplate person would want to consume day after twenty-four hour period and that are easy and quick to prepare after spending long hours at work.

  • The military understands the importance of food. Where a mission to Mars volition last about 1000 d, the military limits the use of meals ready to swallow to 21 sequent days (7). Multiple factors influence loss of body mass in extreme environments, including food acceptability and menu fatigue. During spaceflight, loss of torso mass is associated with musculoskeletal losses, cardiovascular deconditioning, and increased oxidative stress (8).

  • Nutrition. The greatest number of fatalities and mission failures in the history of human exploration on Earth were due to nutrient system inadequacies, such as deficiency of one or more nutrients, insufficient caloric supply and underconsumption, inadequate preservation, or even nutrient toxicities (9, ten). Modern nutrition and food science has prevented these issues on space missions to date, but exploration beyond low-Earth orbit will bring new unknowns. In improver, coming together minimal nutritional requirements may only forbid deficiency, whereas an optimized system (such as ane including a multifariousness of fruit and vegetables and associated bioactive compounds) has the potential to promote health and performance (11, 12).

  • Resource minimization. All resources used (e.yard., mass, volume, crew time, h2o, power, equipment) and all waste product products created (due east.chiliad., waste matter h2o, packaging, volatiles, biological waste) by a food system are weighed against the amount and variety of adequate, nutritious food available for astronauts. Mission planners, with input from health and medical specialists, will determine the health and operation support systems (due east.g., food, exercise, medical) within the larger mission and vehicle resource constraints.

  • Variety. Type, texture, and flavor of food all add together variety. A combination of systems (e.g., prepackaged, grown) may exist needed to avoid menu fatigue. Even a "perfect" food particular, ingredient, or nutrient source cannot provide an entire nutrient arrangement (i.east., it cannot be consumed for every meal).

  • Reliability. Equally is the instance for loss of other systems of a space vehicle, if part or all of a food system is lost, the outcome could exist catastrophic. This could happen if in situ foods do not grow adequately or if equipment malfunctions. All systems must also be validated in real or simulated extremes of the spaceflight environment (eastward.g., pressure, gravity, temperature, radiation).

  • Usability. The nutrient arrangement must be easy and fast for the astronauts to fix or produce food. Exploration missions will have very different goals from colonization missions. Crews of the initial missions will focus on exploration and science, and on these missions, astronauts will gear up food as the average person would in their kitchen after a long day of work. Ideally, astronauts would cook using bulk ingredients, but spacecraft technical considerations can make this difficult, including touch temperature limits (to eliminate the take a chance of burns), safety concerns, and technical challenges with containing and processing ingredients. In addition, food grooming could require resource and processes for cooking and cleanup different from those used in Earth's gravity. Development and testing of such systems must account for the realities and constraints of spaceflight while minimizing resource use. Labor- and resource-intensive nutrient systems may be more feasible during colonization missions than during exploration missions.

  • Space-set appliances. To appointment, space food systems have but immune astronauts to add water and/or warm food (i.e., not cooking). Nutrient preparation equipment had to exist specially developed to run across safety (e.g., touch temperature limits) and spaceflight requirements (e.g., microgravity, motel pressure changes, radiation), often calculation mass. New equipment will need to exist developed for Mars grade missions.

FIGURE i

Requirements of space food systems. A depiction of the many facets of and requirements for space food systems. As described in the text, each element is critical for the ultimate success of a space mission, and failure of any aspect could imperil the mission and the crew. The moon and Mars are also depicted here, reflecting two likely destinations for future human space exploration.

Requirements of space nutrient systems. A delineation of the many facets of and requirements for space nutrient systems. As described in the text, each chemical element is critical for the ultimate success of a space mission, and failure of whatsoever aspect could imperil the mission and the coiffure. The moon and Mars are also depicted hither, reflecting two likely destinations for futurity human space exploration.

FIGURE ane

Requirements of space food systems. A depiction of the many facets of and requirements for space food systems. As described in the text, each element is critical for the ultimate success of a space mission, and failure of any aspect could imperil the mission and the crew. The moon and Mars are also depicted here, reflecting two likely destinations for future human space exploration.

Requirements of space food systems. A delineation of the many facets of and requirements for infinite nutrient systems. Every bit described in the text, each element is critical for the ultimate success of a infinite mission, and failure of any aspect could imperil the mission and the coiffure. The moon and Mars are too depicted here, reflecting 2 likely destinations for hereafter human space exploration.

In the history of humankind, explorers set off to see what was over the horizon, and literally millions did not render because of nutrient and nutrition failures (half-dozen). The harsh reality remains: if we are going to transport humans to the moon and Mars in the coming decade(due south), piece of work needs to be achieved now to ensure the food system fits inside the constraints of space vehicles and sustains and protects astronauts. Nosotros are among those working to understand and mitigate these risks, and we offer this information to others who are hoping to solve nutrient and diet challenges for spaceflight. Nosotros must ensure that the next giant leaps in infinite exploration are well nourished.

Acknowledgments

All authors (GLD, SRZ, and SMS) contributed every bit to the blueprint and writing of this manuscript. All authors have read and approved the draft and final versions of the manuscript. Nosotros thank NASA for support of our work. We give thanks Cindy Bush-league for the graphic.

Notes

Author disclosures: The authors report no conflicts of interest.

This work was funded by NASA, in the form of employment of the authors either directly (GLD, SMS) or through the Human Health and Operation Contract (SRZ).

Abbreviations: ISS, International Infinite Station; NASA, National Helmsmanship and Space Administration.

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Published by Oxford University Press on behalf of the American Society for Nutrition 2020.

This work is written by (a) US Government employee(south) and is in the public domain in the US.