Researchers did a study of the health benefits of seaweed on our gut health, published in Science Direct (2025). Since two-thirds of seaweed consumed by humans are brown seaweed, laminaria and lundaria, the study focused on these species of seaweed.

Scientists found it is a good source of protein and the bioactive compound polyphenols.

Seaweed is also a good source of minerals- potassium, sodium, magnesium and calcium; and rich in vitamins B1, B2, C, E, and β-carotene. Varying by season and species, polysaccharide or fibre content of edible brown seaweeds reaches up to 70 %.

Generally, again depending on which brown seaweed species and the season, researchers found significant increase in Lactobacillus spp., decreased Escherichia coli, and increase in SCFAs (short chain fatty acids). Compounds in seaweed increase the production of SCFAs and influence glucose and lipid metabolism. 

Another study published in Frontiers found that bioactive components contained in seaweed mainly modulate the gut microbiota and gut barrier function by reversing the Firmicutes/Bacteroidetes ratio, increasing the relative abundance of beneficial bacteria, such as Bacteroides, Akkermansia, Lactobacillus, or decreasing the abundance of harmful bacteria, such as Lachnospiraceae, Desulfovibrio, and Lachnoclostridium. 

To top it off, many believe seaweed consumption is the reason for nearly nonexistent prostate cancer among Japanese, compared to 1 in 8 American men.

Seaweed contains bioactive compounds that support prostate health by inhibiting prostate cancer cell growth, and alleviating symptoms of Benign Prostatic Hyperplasia (BPH). In addition to anti-inflammatory agents, brown seaweed contains Fucoidan, Fucoxanthin, and minerals known to support prostate health, including iodine, magnesium and calcium.

https://www.sciencedirect.com/science/article/pii/S1756464625000386

https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2023.1173225/full

https://www.marinova.com.au/news/fucoidan-for-prostate-health/