https://medicalxpress.com/news/2023-01-seaweed-sugar-trigger-immune-responses.html

 L-fucose, a nontoxic dietary plant sugar that is enriched in red and brown seaweeds, can increase TILs, promote antitumor immunity and improve the efficacy of immunotherapy.

https://www.sciencedirect.com/topics/chemistry/l-fructose l-fructose

I am looking if red marine algae would be a good choice