Fucoidans belong to a class of complex sugar molecules known as a polysaccharides. All fucoidans share the same backbone structure, but vary greatly in their molecular composition, and different types show different kinds of biological activities. Fucoidans are found primarily in brown seaweed, but both the level and composition of the fucoidan depends on the exact species of seaweed and the harvest conditions. Preclinical studies in animal models suggest some fucoidans may protect against inflammation and oxidative stress, but there is no strong evidence for similar benefits in humans. Fucoidan consumption is generally regarded as safe.
Brown seaweed extract has been tested in a couple small clinical trials, but no studies have specifically tested the effects of fucoidan on brain health or function in humans. The composition of the fucoidan varied widely across studies.
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Extracts from brown seaweed were found to improve cognitive performance in healthy adults in two small, placebo-controlled clinical trials. One study found that elderly Japanese adults taking a fermented extract of the seaweed Laminaria japonica for six weeks showed improvements in spatial and working memory . The other study showed that consuming a hot water extract of the seaweeds Ascophyllum nodosum and Fucus vesiculosus increased performance on tests measuring alertness and motor speed in young adults . However, seaweed contains many active compounds, and these effects cannot be conclusively attributed to fucoidan.
Fucoidans have been tested for their neuroprotective capacity in a variety of preclinical models for Alzheimer’s disease, Parkinson’s disease, traumatic brain injury, and stroke . Fucoidans have been shown to be neuroprotective when administered close to the time of neurological injury by preventing processes that damage cells, such as inflammation and oxidative stress. These protective effects are thought to be indirect because fucoidans are not expected to reach the brain due to their chemical structure.
Preclinical studies in rodent models of cognitive impairment suggest that only certain types of fucoidan, primarily those with high levels of sulfates, show neuroprotective benefits [4; 5]. However, no studies have shown clinical benefit in dementia patients.
Fucoidan supplementation is safe and showed no evidence of adverse events in clinical studies in healthy adults and cancer patients at high doses up to 4 grams per day [6; 7]. Long term dietary consumption of fucoidan is also expected to be safe based on an estimated daily fucoidan intake of 400 mg in Japan where diets are rich in seaweed . Excessive consumption of seaweed could increase the risk for thyroid disorders due to its high iodine content. Fucoidans may slightly increase bleeding risks in people taking blood thinners. The strong safety record may be due to the very low bioavailability of currently available sources of fucoidan.
NOTE: This is not a comprehensive safety evaluation or complete list of potentially harmful drug interactions. It is important to discuss safety issues with your physician before taking any new supplement or medication.
Fucoidans are rich in brown seaweed such as, Kombu (Saccharina japonica), Wakame (Undaria pinnatifida), Hijiki (Sargassum fusiforme), Nori (Pyropia tenera), and Mozuku (Nemacystus decipiens). The fucoidan content typically ranges from 0.5-13% of the dry weight, but can be as high as 69% under certain conditions, and is highest in seaweed harvested in late autumn/early winter . Seaweed is also rich in other minerals and compounds that might increase the bioactivity of the fucoidan. Daily intake of 2 grams of dry seaweed is associated with reduced risk for various diseases . Fucoidans are also available in supplement form, however, the composition of the fucoidans can be altered during the extraction process, and there is no clinically validated form of fucoidan extract that has been shown to have therapeutic benefit .
Information on the clinical uses and safety for seaweed on Drugs.com
Information on the uses, mechanism of action, and safety of fucoidan from the Memorial Sloan Kettering Cancer Center