Beyond nutrients: The multifaceted significance of food

What significance does food have in our lives? Why can't we live on nutrient bars or nutrient-dense shakes? Well, food goes beyond nutrition. It is important to recognize the significant role that food plays in our lives, beyond being a source of nutrients, as it also contributes to our cultural, social, and emotional well-being. Its sensorial qualities, encompassing taste, texture, smell, freshness, and variety, greatly influence our dining experiences. Food also holds an emotional aspect, serving as a source of comfort and nostalgia, reminiscent of our connection to certain parts of our lives, or for astronauts, Earth. Socially, it facilitates the act of sharing meals, fostering communication, and providing opportunities for gathering and engaging in meaningful, or meaningless conversations. Not to be forgotten is that the environment where to food is consumed also shapes our dining experiences.

This is something that becomes more and more apparent when we are trying to feed people in space.

There is a lot to write about within this subject and the following article might be a bit dense. But it really just scratches the surface of the actual subject.

Taste and smell

Regardless of how much nutrients food contains, it must be eaten to fulfill its purpose as a nutritional sustenance. Our chemical senses, such as taste, ortho - and retronasal contribute significantly to the sensory effects of food choice, appetite, and intake. Taste works as a sensing system for macronutrients (carbs, fats, and proteins), and along with texture, it determines the duration of the oral exposure, or how long we are chewing the food. The smell triggers what we call a priming process and induces the appetite, which in turn triggers a complex signaling system in our body, preparing us for what we are going to eat.

This makes flavor the most important determinant of quality.

What have we learned from previous space missions?

What I have stated above became more apparent during the Mercury missions (1961 - 1963). The food on these missions served all of the nutritional requirements, but it had some objectionable features; the crew could neither see nor smell the food since it was served in tubes similar to toothpaste tubes. This was… well, less than appealing. Due to its lack of organoleptic appeal, the astronauts did not eat all of the food provided, leading to malnutrition.

There were similar problems with bite-sized cubes, similar to fruit and nut bars. The cubes did not have a familiar mouth feel and taste which resulted in that many of them remained uneaten. A similar issue was found with freeze-dried powders which were hard to rehydrate, resulting in crumbs, posing a risk to the spacecraft’s instruments.

The Gemini missions (1965 - 1966) saw an evolution in space food, but the changes primarily addressed the packaging for safety reasons. This attention birthed the Hazard Analysis and Critical Control Points (HACCP) system – now a cornerstone of the food industry.

However, these improvements did not necessarily translate to tastier meals. Astronauts still relied on tube-based foods and those energy-packed cubes. Even though the food was deemed acceptable in ground-based tests, it did not meet the requirements in space and the decrease in acceptability led to a significant weight loss and malnutrition of the astronauts.

It was first in the Apollo missions (1968 - 1972) that malnourishment gained some serious attention. Astronauts' declining interest in their meals was not just about the food's taste (or lack thereof). Now an additional issue raised. The monotony of their diet, coupled with the lack of stimuli in a boring confined environment, or the sensory deprivation of space dampened their appetites. With this acknowledgment, the foods on the later Apollo missions deviated from the tubes and cubes and were developed further to open container foods with utensils, which provided the astronauts with an eating experience that was somewhat reminiscent of Earth.

However, despite all of the improvements to the food, the astronauts still did not consume the proper amount of nutrients, and much of the food was left uneaten. It became more apparent that the food needed to develop further with a greater focus on palatable and familiar-tasting foods.

So, what do we need to do for longer missions into deep space?

Now, imagine being on a long-haul flight to Mars, or on a longer mission to the Moon. Here is where food really becomes more than just a functional source of nutrients. Aside from the sensorial qualities such as taste, texture, smell, freshness, and variation, the food needs to fulfill emotional, social, and environmental aspects, which all relate to basic human psychological and biological needs.

Traversing into deep space, astronauts have to deal with various psychological challenges that cause a high level of stress, which in turn may alter their physiology. To live in a confined space, with limited habitation volume, reduced living quality, and environment as well as the absence of fresh air, are all aspects that affect human psychological health negatively.

In addition to these basic needs, astronauts may face reduced sensory stimulation and boredom due to strictly regulated work and rest schedules, delays in communication with Earth, and the absence of loved ones may all reflect upon the psyche of the crew. Another important factor to consider is that missions to Mars will be the first time humans have to deal with the “earth out of view” phenomenon. Now imagine that… This separation from Earth may lead to extreme pathological separation anxiety, which in turn could trigger an out-of-control existential crisis.

There is a synergic effect between physiological and psychological health, if one is deficient, the other suffers. These synergic effects might also be magnified by environments different from the ones where we evolved, and to minimize these mismatches between space and Earth, it is imperative to accommodate the fundamental human needs. It is therefore very important to consider the effects of food as a countermeasure to these psychological stressors.

The importance of food in isolated environments

When we think of ways of sustaining astronauts with food, we should consider all aspects of food, even the ones that are otherwise overlooked. For instance, the emotional aspects of food can be used as a reminiscent of life back on Earth, where food is commonly used as comfort. The social concept of food should also be taken into consideration, since sharing a meal with someone or making food a shared social experience has positive psychological aspects.

Several studies have highlighted the importance of food in isolated environments and the function food has to build morale in isolated micro societies, where dining is one of the few social events during the day that encourages communication. Journals from over 100 polar expeditions have been analyzed and out of all the categories mentioned, food was one of the most important ones that had the most positive entries. The expedition members viewed the food as compensation for living and working in harsh environments.

So how does the space environment affect our senses?

When exposed to microgravity, bodily fluids shift from the lower part of the body to the upper part, which causes facial edema and in turn congests the nasal passages. Very similar to a cold. This results in a loss of direct smell as well as a part of the retronasal stimulation. This is actually very important for certain perceptions of sensorial qualities. For instance, orange juice tastes sweet because the aroma of the orange increases the perception of sweetness retronasally. With a reduction of retronasal stimulation, it would taste bland and sour.

Radiation also affects astronauts' taste and odor receptors, decreasing the perception of sweet and sour. On shorter missions in space and on the International space station (ISS), the astronauts will not be exposed to these levels of radiation, but for future Mars missions, the prolonged and high exposure to radiation needs to be taken into consideration. These factors combined with environmental factors in the spacecraft or habitat can also create a synergic effect. A higher oxygen concentration and lower atmospheric pressure, combined with the monotony of the surroundings, can dull our senses, making food taste different and not as satisfying.

Emotional factors come into play too. The stress of being in space can change the makeup of our saliva, making certain foods taste more bitter. It can also lessen the impact of flavors like sourness.

Can we tweak the food? Adjust the recipe or change the texture? Well, that's another challenge that behaves quite differently in space. More on that will be covered in a future article.

Closing remarks

A lot has happened regarding food systems in space over the last 60 years. However, most of the research has been driven to develop food for the crew on board the ISS. With a reinvigoration of space travel and new plans to go beyond the low earth orbit and the moon into deep space and to Mars, a plethora of new challenges regarding the development of food systems for these missions has been introduced. Before we can send humans into a confined environment for a long period of time, deprived of sensorial stimulation, it is essential to take basic human needs into account and what role food plays for the psychological well-being.

The significance of the organoleptic appeal and the social and environmental aspects of food will become more apparent when living in a confined space, deprived of other sensorial stimulation. When designing food solutions for deep space missions, it is important to consider that food is more than a functional source of nutrients and the many psychological aspects of food that may be taken for granted in everyday life should not be overlooked.