Human trials have demonstrated that the world’s “most exhaustively studied algae” – Chlamydomonas reinhardtii – improves symptoms of irritable bowel syndrome, including diarrhoea, gas and bloating.

Ironically, the green, single-celled organism, which primarily grows in wet soil, has for decades “served as a model species for research topics spanning from algae-based biofuels to plant evolution.”

But the benefits for people consuming the algae went unexplored, until now.

Assumed to be nutritious, suspected health benefits

“People have been looking at this algae for decades, but this is the first study to show what many of us have suspected – it’s good for you,” said principal investigator and algae expert Stephen Mayfield, director of the California Centre for Algae Biotechonology, distinguished professor in UC San Diego’s Division of Biological Sciences and co-director of the Food and Fuel for the 21st Century Program.

“This is exciting because it demonstrates a clear benefit: If you have IBS-like symptoms, this is good for you.”

A graphical abstract of the research. Illustration: UC San Diego

According to a statement from the University of California San Diego, preliminary data in mouse studies demonstrated that consuming Chlamydomonas reinhardtii “significantly reduced the rate of weight loss in mice with acute colitis, which is generally linked to inflammation of the digestive tract.”

The algae species used in the study was “subject to rigorous safety testing” and designated as “Generally Recognized As Safe” by the U.S. Food and Drug Administration – thus green-lighting the use of the algae in a study using human volunteers, including those with and without symptoms associated with IBS.

How does it work? Unknown as yet

In powdered form, the algae is said to be a very nutritiously dense substance: 40 to 50 per cent protein, 10 to 20 per cent oil, “some carbohydrates, some fibre and lots of vitamins.”

Volunteers consumed daily spoonfuls of powdered C. reinhardtii – which apparently tastes like matcha green tea – and reported their gastrointestinal health for one month.

Results showed that participants who suffered from a history of frequent gastrointestinal symptoms reported significantly less bowel discomfort and diarrhoea, significantly less gas or bloating and more regular bowel movements.

“The benefits of consuming this species of algae were immediately obvious when examining the data from both mice and humans who suffered from gastrointestinal symptoms,” said Frank Fields, a research scientist in Mayfield’s lab and lead author of the paper.

Chlamydomonas reinhardtii: Call it clammy for short. First human trials are encouraging for this this species of alga as a treatment for IBS issues. Otherwise, it’s a highly dense nutrient. Photo: Malcolm Storey

These are early days and the researchers say much more testing with larger groups of participants across longer time periods is needed. At this point, they are unclear about how the algae works to improve gastrointestinal health.

The scientists say the benefits could be traced to a bioactive molecule in algae or perhaps a change in gene expression of gut bacteria caused by algae consumption.

Other species of algae have been used as dietary nutraceuticals that provide beneficial oils, vitamins, proteins, carbohydrates, antioxidants and fibre.

Probably the best known alga nutraceuticals is Spirulina, a blue-green alga that became famous after it was successfully used by NASA as a dietary supplement for astronauts on space missions. It’s a good food but is it an effective treatment nutraceutical? For two assessments of Spirulina’s many purported health-boosting properties, see here and here.

Video report by Shalina Chatlani, courtesy KPBS San Diego