This is Part 2 in the Menu Fatigue series. Catch up on Part 1 here or skip ahead to Part 3. Check out A Complete History of Space Food for more background on efforts to introduce menu variety on space missions.
Previously, we explored the general psychophysiology behind menu fatigue, or Sensory Specific Satiety (SSS). Based on previously conducted research, SSS is not just emotional boredom, but deeply rooted in unconscious physiology – to the extent that amnesiacs grew tired of repeated exposure to a food and rated the taste as increasingly unpleasant, even though they still felt hungry, had previously enjoyed the food, and had zero memory of eating it.
Space mission menu diversity is a challenge that NASA has grappled with over half a century. The challenge is twofold: 1) Keeping up with food technology that allows crew members to eat semi-normal foods in a space-and-resource limited environment, and 2) Providing sufficient variety to avoid boredom and inadvertent drop in consumption of essential nutrients.
Menu Fatigue on Previous Missions: Underconsumption and Weight Loss
Okay, but… we’re talking about astronauts here. They’re not going to space for a Michelin 5 star experience. Could they just, you know, suck it up and eat stuff they’re bored with for a few months? It’s space, not Hell’s Kitchen.
Well, not really. Based on concerning body composition changes on previous missions, we can’t dismiss this problem as a question of astronauts’ willpower. It’s already proven to be a problem. In a study of meal replacement bars (MRBs) for isolated environments and possible future missions, Sirmons et. al.1 noted,
It is often assumed that high-performing, highly-trained individuals such as astronauts will eat whatever is required, regardless of quality or appeal, to maintain nutritional status and successfully complete a mission. On the contrary, food familiarity and quality assume added psychological importance on extended-duration space missions, where it may mitigate stress associated with prolonged isolation and confinement. Limited variety or palatability can be a source of increased stress.
Sirmons, et. al.
Established Underconsumption
If the food isn’t palatable, it won’t be sufficiently consumed to avoid nutrient deficiencies. On previous missions, astronauts have been found to lose an average of approximately 2-5% of their pre-flight weight. Sometimes, weight loss is as high as 10%. This is on relatively short missions compared with a trip to Mars or beyond, and while such weight loss might level off, the health consequences could be dire. Astronauts have the training and knowledge to fully understand the importance of adequate oral intake. However, they tend to consume an average of 25-30% less than usual during a mission.2
Along with psychophysiological reasons for SSS, studies have suggested that the microgravity environment on space missions leads to an increase in two hormones that increase satiety: Leptin and GLP-1.2 Additionally, the exercise required for maintenance of bone mass and overall conditioning increases astronauts’ energy expenditure, exacerbating the problem.
Commodity Theory
Astronauts aboard the ISS have affirmed the psychological benefits from deliveries of fresh fruits and vegetables several times each year. Could this mean that underconsumption might be just a simple case of “I want what I can’t have?” The previously discussed study examining physiology vs. psychology in SSS asked the question of whether “Commodity Theory” was responsible for menu fatigue. Wilkinson and Burnstrom define Commodity Theory as a description of “the relative increase in value of a commodity when it becomes unavailable.”3
In the study, participants were given a test meal (the eaten food). The groups were then told about an alternative food (the uneaten food); some were told they would have access to the uneaten food and some were advised that they would not. The authors hypothesized that satiety for the eaten food would decline more sharply when participants were told that they would not have access to a different food. Surprisingly, this wasn’t the case, leading them to the conclusion that SSS/menu fatigue was more innate physiological rather than the result of higher cognition or pure mental boredom.3
Implications for Mars and Beyond
Missions aboard the ISS range from 4-6 months to nearly one year, the record holder being Mark Vande Hei with a stay of 355 consecutive days. Scott Kelly hold the previous record, clocking in at 340 days.4 Kelly and his twin brother Mark, who is also a NASA astronaut and now a United States senator, underwent a series of “twin tests” to determine how a lengthy space vacation affects overall health, genes, cognition, and body composition. While on the ISS, Kelly lost a total of 15 pounds.5
A speculated journey to Mars will take a good 6 months in one-way travel. Add in an 18 month stay on the surface and another 6 month journey home, and we’re looking at a mission of at least 2.5 years. Now take away the established food systems and menu diversity on the ISS, and forget about the semi-annual fresh food deliveries. This could put crew members on a vicious downward cycle of increased needs and lack of resources for sufficient intake.
The previously mentioned study of meal replacement bars (MRBs) was conducted to determine if standardized bars would be an appropriate solution for decreasing overall food system mass on upcoming lunar missions. The MRBs were approximately 750 kcals, meant to replace the energy and nutrients of one meal. In a 30-day closed chamber study, reliance on these bars for one meal/day led to an overall reduction of caloric intake, along with decrease in morale.6
If we’re going deeper into space, we need to figure menu fatigue out. Food systems are going to be essential to the success of these missions.
Space tourism
We’re hoping to regularly send non-astronauts to space eventually, possibly even on extended missions. This won’t even be an option if we can’t figure out how to get enough food into not only highly-trained astronauts, but regular people on a lunar joyride. Though perhaps not of immediate concern, there’s going to be a lot of “I’d like to speak to the space-manager, please” if the food isn’t up to par.
Coming up in Part 3, we’ll look at some possible solutions.
Sources
1. Sirmons TA, Roma PG, Whitmire AM, Smith SM, Zwart SR, Young M, Douglas GL. Meal replacement in isolated and confined mission environments: Consumption, acceptability, and implications for physical and behavioral health. Physiol Behav. 2020 May 15;219:112829. doi: 10.1016/j.physbeh.2020.112829. Epub 2020 Feb 14. PMID: 32068108. / 2. Tang et. al. Long-term Space Nutrition: A Scoping Review. Nutrients. 2022, 14 (194). https://doi.org/103390/nu14010194 / 3. Wilkinson LL, Brunstrom JM. Sensory specific satiety: More than ‘just’ habituation? Appetite. 2016 Aug 1;103:221-228. doi: 10.1016/j.appet.2016.04.019. Epub 2016 Apr 20. PMID: 27105584; PMCID: PMC4910838. / 4. Garcia M. NASA Station Astronaut Record Holders. NASA. https://www.nasa.gov/feature/nasa-station-astronaut-record-holders / 5. Krieger L. How a Year in Space Changed Scott Kelly. The Mercury News. https://www.mercurynews.com/2019/04/11/how-a-year-in-space-changed-astronaut-scott-kelly/ / 6. Douglas G, Zwart S, and Smith S. Space Food for Thought: Challenges and Considerations for Food and Nutrition on Exploration Missions. The Journal of Nutrition, Volume 150, Issue 9, 2242-2244. https://doi.org/10.1093/jn/nxaa188