The Diet-Mental Health Relationship in Astronaut Performance
The discipline of nutritional psychology is consolidating evidence worldwide on how dietary intake can impact various aspects of psychological, behavioral, cognitive, and functional performance in work environments (see the Diet and Human Performance research category within the NPRL). This includes how we think, behave, and perform in many workplace environments — from shift workers in hospitals (Leedo et al., 2017) and long-haul truck drivers (Ge et al., 2021) to students in the classroom (Barchitta, 2019), pilots in the cockpit (Lindseth, et al., 2011), and astronauts aboard space stations (Douglass, 2022).
NASA’s Human Exploration Research Analog (HERA) experiment compared the psychological and health effects of the standard diet currently served to astronauts on the International Space Station (ISS) with a new, enhanced diet formula. Results showed that study participants who ate a diet containing more fruits, vegetables, fish, and foods rich in flavonoids and omega-3 fatty acids had lower levels of cholesterol, reduced stress (as indicated by the hormone cortisol), better cognitive speed, accuracy, attention, and a more stable composition of gut microorganisms compared to participants who ate the standard International Space Station diet. The study was published in Scientific Reports.
Adding more fruit, vegetables, fish, and foods rich in flavonoids and omega-3 fatty acids to astronauts’ diets improves psychological, cognitive, and health-related outcomes.
What do astronauts eat?
Since the start of spaceflight over half a century ago, the food available to astronauts during space missions has improved dramatically. Early astronauts had very limited dietary choices, typically consisting of prepackaged foods served in either squeeze tubes or bite-sized cubes coated in gelatin to prevent the formation of crumbs. This was crucial in the confined environment of a space vessel, where loose food particles could pose a serious long-term health threat (Perchonok & Bourland, 2002).
Food options for astronauts have dramatically increased, as have the number of days astronauts routinely spend in orbit during a single mission. Longer duration missions, like those on the International Space Station (ISS), have increased the importance of spaceflight menus, allowing astronauts’ diets to be as Earth-like as possible. Today’s space foods include various food items packed in single-serving containers.
Longer space missions require more earth-like food items and menus to address astronauts’ psychosocial and psychological needs.
Modern spaceflight menus are typically organized into 6 or 7-day rotations, consisting of four meals per day – breakfast, lunch, dinner, and a snack. Food menus are planned based on the astronauts’ weight to provide the calories and nutrients required to maintain their health.
In the early days of spaceflight, experts believed they could calculate the ideal food composition for astronauts based solely on nutritional requirements for survival in space. However, the current perspective recognizes that “ideal food cannot ensure psychosocial comfort, while a grandma-style pie can” (Bychkov et al., 2021). Longer space missions have highlighted the importance of food beyond just nutritional survival needs, taking into account the diet-mental health relationship. This includes considering the psychological, cognitive, behavioral, and psychosocial value of food for the well-being of astronauts.
With this in mind, modern astronauts can select around 20% of their food items and beverages, while around 80% of their diet comes from a shared standard set of foods (Douglas et al., 2020).
Consistent with nutritional psychology-related factors, “Ideal food cannot ensure psychosocial comfort, while a grandma-style pie can” (Bychkov et al., 2021).
How is the food for astronauts prepared?
Food items are specially prepared on Earth before a flight to make them easy to use in a weightless environment and to minimize the risk of spillage. Spillage is dangerous in weightlessness as spilled material will not drop to the ground but disperse around the room or form free-floating bubbles. Crumbs or very small granules can also be dangerous and difficult to collect. For example, salt and pepper are available to astronauts in liquid form.
The food items need to be shelf-stable, either in their natural form or preserved by removing water and sterilized using heat or radiation. On the International Space Station, resupply vehicles arrive several times a year, bringing fresh fruits and vegetables and some semi-shelf-stable specialty items. Astronauts report that these deliveries provide profound psychological benefits (Douglas et al., 2020).
Astronauts report that these deliveries [fresh produce] provide profound psychological benefits (Douglas et al., 2020).
While NASA has successfully provided food for missions of up to 11 months in low Earth orbit (Douglas et al., 2020), plans for future deep-space manned exploration missions make space nutrition a topic of intense scientific research.
What is HERA?
The Human Exploration and Research Analog or HERA is a two-story building at the NASA Johnson Space Center (JSC) in Houston. Its purpose is to simulate the isolation, confinement, and remote conditions of space exploration scenarios. The building contains four habitats that simulate a space vessel with its simulated airlock and hygiene module.
HERA is used for studies that consist of 4 crew members living in the enclosed space of the simulated vessel for up to 45 days. One such stay is called a mission. During a mission, study participants stay in the habitat, spending their time in the way they would spend on a real space mission (with the difference that they are not weightless).
The simulation vessel crewmembers did not have access to the internet, social media, or communication outside mission control. They could communicate privately with their family, medical personnel, or a psychologist once a week. There was a limited selection of movies or music through a controlled account. HERA research studies last up to 68 study days (NASA ROI – Flight Analogs Human Research Program, 2019) and involve 16 days of preparation before entering the habitat and 7 days of follow-up after leaving it.
Plans for future deep-space manned exploration missions make space nutrition a topic of intense scientific research.
The study of health and psychological effects of an enhanced menu
A new study by Grace L. Douglas — an experienced researcher on the health effects of spaceflight working at the Human Health and Performance Directorate of the NASA Johnson Space Center in Houston — and her colleagues explored whether the diet of astronauts can be further improved (Douglas et al., 2022). They reasoned that studies investigating the effects of spaceflight nutrition conducted thus far have focused only on a limited number of nutrients and outcomes. They wanted to test how further increasing the variability and availability of healthy, shelf-stable, space flight-compatible foods that included fruits, vegetables, fish, and other foods rich in flavonoids and omega-3 fatty acids would affect the immune system, gut microbiome, nutritional status, and cognitive outcomes of future astronauts.
Study participants and procedure
The study participants were sixteen individuals with an average age of 40 and body mass indexes that placed them in the healthy weight range. Ten of the study participants were men, and 6 were women. These sixteen individuals participated in four 45-day HERA missions (four people per mission) conducted in 2017 and 2018. Each participant participated in a single mission. They were instructed to keep logs of the food and beverages they ate and drank 15 days before the mission.
After they entered the HERA habitat and started the mission, participants were not allowed to select any menu components. Trading food items was also not permitted. This is because the researchers wanted to make the study as consistent as possible with real-life situations in future space exploration missions. Food and beverages that the participants were expected to consume during the mission were stowed in the habitat at the beginning of the mission. All participants received the same base menu in each mission.
The standard International Space Station menu and the new enhanced menu
The menu was designed to provide the nutrients required to stay healthy with approximately 2300 calories daily. An additional 100 to 200 calories per person were provided “to ensure adequate provisioning with minimal choice.” Participants were instructed to consume the base menu before consuming additional calories.
Researchers randomly selected two missions to receive the new enhanced menu they designed, while the other two missions received the standard International Space Station menu. Study participants were not told which menu they were receiving during the mission they participated in.
Measures and assessments
After each meal, participants recorded actual food consumption using the International Space Station Food Intake Tracker iPad App. Researchers recorded the use of antibiotics and medications. Weight and height were measured before the mission and weight measurements were taken before breakfast each day during the mission.
Researchers collected blood, stool, urine, and saliva samples from each subject at 5-time points – twice before and 3 times during the mission. The collection of samples during the mission was done in a special HERA chamber and transferred out through a pass with minimal to no contact between the study participants (HERA “crew”) and the support team.
From these samples, researchers assessed levels of vitamins, flavonoids, calcium, and bone health, cardiovascular and fluid regulation, metabolic, oxidative stress, reproductive hormones, and iron and blood cell concentrations. They also conducted immunological analysis and assessed levels of the hormone cortisol and viruses from saliva. Researchers determined the composition of the gut microbiome from stool samples of participants and conducted a study of gene expressions of these microorganisms. The latter procedure is called metatranscriptomic analysis.
As part of a broader Cognition test battery (see Figure 1), participants completed vigilant attention assessments using the Psychomotor Vigilance Test (PVT) twice before the mission and three times per week during the mission.
Figure 1. Crewmember measures and assessments protocol
Nutritional intake was improved for participants consuming the enhanced diet
Results showed that study participants in both groups did not fully consume their menu items. However, participants in the enhanced menu missions consumed more servings of fruits and vegetables per day, and ate more fish per week and more servings of tomato-based foods.
The participants receiving the enhanced diet took in more calcium, potassium, daily fiber, and omega-3 fatty acids than participants on the two standard menu missions (see Figure 2). The importance of omega-3 fatty acids comes from the fact that they are an integral part of cell membranes in the human body. They are also starting points for producing hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation. Intakes of protein, sodium, and iron were similar in the two groups.
Crewmembers on the enhanced diet took in more calcium, potassium, fiber per day, and omega-3 fatty acids than participants on the standard menu missions.
Figure 2. Enhanced menu missions consumption
The enhanced menu and health indicators
General health status was similar in participants consuming the two diets. However, cholesterol status was improved in participants consuming the enhanced diet. They also had higher physiological flavonoid concentrations in urine and more stable fatty acid concentrations in the blood (see Figure 3).
The concentration of the hormone cortisol in the blood was higher in participants on standard diets. Cortisol is a hormone produced by adrenal glands. It regulates the body’s response to stress. Higher concentrations are indicative of higher stress levels.
The diversity and richness of gut microbiota were reduced in participants consuming the standard diet. Researchers also detected changes in the abundance of several species of gut microorganisms that were associated with the differences in the diet. Additionally, gene expression profiles, i.e., metatranscriptomic profiles of the gut microbiome, were more stable for subjects consuming the enhanced diet.
Cognitive speed, accuracy, and attention were better for subjects consuming the enhanced diet
Psychological assessments showed that cognitive speed, accuracy, and attention were better for subjects consuming the enhanced diet. The reaction speeds in the tests of study participants consuming the enhanced diet were higher than the average reaction speeds of participants on the standard diet and improved compared to their pre-mission results.
Figure 3. Enhanced vs Standard diet
The study showed that a specific diet rich in fruits, vegetables, and omega-3 fatty acids produces significant health and performance benefits in a simulated space exploration mission environment. Countering the physiological deterioration of astronauts’ health during long space missions is an ongoing goal for researchers and mission planners. These results can help achieve this goal by better planning food resources and astronauts’ menus and lend credence to the importance of the diet-mental health relationship on human performance and within work environments.
The paper “Impact of diet on human nutrition, immune response, gut microbiome, and cognition in an isolated and confined mission environment” was authored by Grace L. Douglas, Diane DeKerlegand, Holly Dlouhy, Nathan Dumont‑Leblond, Eden Fields, Martina Heer, Stephanie Krieger, Satish Mehta, Bridgette V. Rooney, ManolitoG.Torralba, Sara E. Whiting, Brian Crucian, Hernan Lorenzi, Scott M. Smith, Millennia Young, and Sara R. Zwart.
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