NASA discovers that space lettuce is not a solution for feeding astronauts

A NASA affiliated study analyzed lettuce grown on the International Space Station and China’s Tiangong II. It found that the crop carries about 30 percent less calcium than Earth lettuce.

This matters because crews headed for Mars will live on stored meals and fresh harvests for years. Bones already lose calcium in microgravity, a weightless environment where fluids shift and cells sense little pull from gravity.

What happened to the lettuce

The research compared space leaves to ground controls grown under the same light and timing. Mineral tests showed clear shifts between the two sets.

The work was led by B. Barbero Barcenilla at Texas A&M University. The research focuses on space nutrition and how plant and human biology change in orbit.

Calcium and magnesium fell in orbit, potassium often rose, and iron varied. These shifts were documented in an ISS lettuce analysis that measured minerals and plant antioxidants.

NASA’s Plant Habitat 07 is now testing how water levels shape growth, nutrients, and the plant microbiome. The ground team harvested Outredgeous romaine for control.

Why microgravity bends plant nutrition

Spaceflight changes how roots move water and pull minerals, which can scramble cell chemistry. One result is lower phenolics, small antioxidant molecules that help plants handle oxidative stress.

In one veggie run on station, total phenolics dropped while overall antioxidant capacity stayed steady. That pattern suggests stress responses, not just a simple loss of food quality.

The synthesis team also flagged carotenoid shortfalls, pigments that support vision and immunity. Fewer carotenoids mean less built in protection for leaves under radiation and bright light.

Space lettuce is not weaker across the board. Potassium stayed stable on the ISS and ran higher on Tiangong II, showing a nutrient mix that shifts rather than a flat decline.

Astronaut health is part of the same loop

The same analysis reviewed 163 calcium related genes and found several that changed during flight. That pattern tracked with higher bone turnover markers measured in space.

Emerging evidence points to leaky gut, a more permeable intestinal wall that lets irritants slip into blood. A recent review ties astronaut and rodent data to barrier problems during missions.

In the NASA Twins Study, Northwestern researchers saw the gut microbiome shift and then rebound after landing. 

Scientists emphasized that missions to Mars cannot proceed safely without a deeper understanding of how spaceflight affects both the human body and the microbes that travel alongside astronauts.

If fresh crops bring less calcium and fewer antioxidants, diet alone will not offset bone loss. That is a tight spot for crews living months beyond low Earth orbit.

What NASA is testing next

One path is biofortification, breeding or engineering plants to carry extra minerals useful to crews. Researchers also outline targeted supplements for the gaps most likely to emerge.

Another tactic is to grow leaves and herbs naturally rich in flavonoids. Soybean sprouts, parsley, and garlic are candidates for early trials in station greenhouses.

NASA is also closing cultivation gaps that make minerals swing. Plant Habitat 07 will map moisture control so roots can take up nutrients without stress spikes.

Crews will not eat leaves alone. Fermented foods can carry vitamins, amino acids, and living microbes that train the immune system.

Microbes can help carry the load

A 30 day experiment fermented miso and returned a safe, flavorful paste. The batch tasted nuttier and showed unique microbial and genetic signatures in orbit.

Space fermentation does more than season dinner. It proves that friendly microbes can work in microgravity, which strengthens the case for yogurt-like or miso-like foods onboard.

Properly designed ferments may also support gut barrier health. That could counter risks flagged in the astronaut permeability review.

Together, leaves plus ferments offer a flexible way to add nutrients without heavy supplies. Every extra gram produced onboard is a gram not launched from Earth.

What this means for Mars missions

A crew bound for Mars will eat stored food for months, then lean on station farms. If those crops show lower mineral payloads, health margins shrink.

Calcium losses in food stack onto bone losses in flight. That double hit can raise fracture risk and fatigue if menus do not adapt.

Menus will need redundancy and monitoring. Flight surgeons and horticulturists can treat food like a medical system, not just a pantry.

With better cultivars, tuned lighting, and measured ferments, crew diets can recover lost ground. The task now is to turn careful lab plans into everyday meals.

Designing resilient space farms

Teams can start by defining bioavailability, the share of a nutrient the body can absorb. Plant choices should reflect absorption first, not raw content.

Sensors should track minerals and phenolics at each harvest. Real time metrics will catch problems before they reach a plate.

Growth systems should practice targeted watering, salinity control, and staged harvests. That steadies roots and keeps stress chemistry from overwhelming nutrition.

The study is published in NPJ Microgravity. 

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