Chlorella and Spirulina are unicellular algae that are rich in proteins and are commonly used as food supplements, even by space travelers. These algae have several characteristics that make them suitable for supplementation.

1. Chlorella:
Chlorella is a genus of green algae that is spherical in shape and has a single cell. It is known for its high protein content and is often used as a dietary supplement. Some key points about Chlorella include:

- Rich in protein: Chlorella has a high protein content, with around 50-60% of its dry weight being protein. This makes it an excellent source of essential amino acids.
- Nutrient-rich: Chlorella is also rich in vitamins, minerals, and antioxidants. It contains vitamins B, C, and E, as well as minerals like iron, calcium, and magnesium.
- Detoxifying properties: Chlorella has been shown to have detoxifying effects due to its ability to bind to heavy metals and other toxins in the body, aiding in their elimination.
- Immune support: Some studies suggest that Chlorella may boost the immune system, potentially reducing the risk of infections.

2. Spirulina:
Spirulina is a blue-green algae that grows in freshwater and is also used as a dietary supplement. It has been consumed for centuries and is known for its high nutritional value. Some key points about Spirulina include:

- High protein content: Spirulina is a complete protein source, containing all essential amino acids. It is estimated to be about 60-70% protein by dry weight.
- Rich in vitamins and minerals: Spirulina is a good source of vitamins A, B, C, and E, as well as minerals such as iron, magnesium, and potassium.
- Antioxidant properties: Spirulina contains various antioxidants, including phycocyanin, which gives it its blue-green color. These antioxidants help protect cells from damage caused by free radicals.
- Potential health benefits: Studies have suggested that Spirulina may have various health benefits, including improving immune function, reducing inflammation, and lowering cholesterol levels.

In conclusion, both Chlorella and Spirulina are unicellular algae that are rich sources of protein and other nutrients. Their high protein content, along with their vitamins, minerals, and potential health benefits, make them popular as food supplements, even for space travelers who require nutrient-dense and easily digestible foods.