Edible seaweeds(macroalgae) have become a hugely popular addition to Western diets in recent years.
In Asian countries such as Japan, seaweeds play a significant role in the diet and one-fifth of meals can be based around various types of edible sea vegetables.
Seaweeds are a healthy low calorie and sustainable plantbased source of many macro and micro-nutrients such as B-complex vitamins, trace elements such as iodine and even small quantities of essential fatty acids.
Sea vegetables also contain a range of unique and interesting bioactive components such as the polysaccharides(alginates, fucoidan), carotenoids (eg, fucoxanthin) and many others which have peaked the interest of scientists researching into functional foods for the health and nutraceutical industries.
Examples of edible seaweeds include Kelp, Dulse, Nori, Wakame, Kombu, Bladderwrack and Sea Lettuce.
In this article we are going to look at some of the key nutritional and evidence-based health benefits of edible seaweeds.
1. Seaweeds Are The Richest Dietary Source Of Iodine
Seaweeds are the richest plantbased dietary source of the trace element iodine, which is essential for the synthesis of thyroid hormones such as triiodothyronine (T3) and thyroxine (T4).
Iodine content greatly varies between the different species of edible seaweeds with nori containing the lowest iodine content and the likes of kombu being some of the richest.
Low iodine status is still common in many parts of the world including the UK and vegans in particular may be at-risk of developing iodine deficiency. Seaweeds are an easy way to boost iodine intake and meet your daily requirements.
2. Seaweeds As A Source Of Protein
Seaweeds are a decent plantbased source of protein and contain all amino acids, especially glycine, alanine, arginine, proline, glutamic, and aspartic acids.
Edible species protein content generally ranges anywhere between 5-47% of dry weight.
On a gram-for-gram basis, seaweeds have protein and amino acid contents comparable to those of beef; however, seaweeds are consumed in much smaller quantities. 
3. Seaweeds, Dietary Fiber & Polysaccharides
Edible seaweeds are rich sources of dietary fiber and contain a range of unique fiber components that have been studied for their anti-obesity effects, ability to potentially improve metabolic health, support intestinal health, amongst other health benefits.
Brown seaweed for example contains alginate, laminarin and fucoidan polysaccharides.
Red species of seaweed contain agar, carrageenan, porphyran, and xylan; and green seaweeds contain ulvan, xylan, and cellulose.
Due to the rich fiber content seaweeds have been proposed to have a “prebiotic” effect, feeding and stimulating the beneficial gut bacteria and supporting intestinal health.
4. Source of Vitamins
Sea vegetables are a good source of many vitamins including the B-complex group, Vitamin A(beta-carotene), Vitamin E and even a little Vitamin C.
Interestingly, purple laver also known as Nori has shown in studies to contain substantial quantities of bioactive forms of Vitamin B12, making it a potential valuable non-animal based Vitamin B12 dietary source for vegans. (approximately 63.6 μg/100 g dry weight and 32.3 μg/100 g dry weight, respectively).
Edible purple laver predominantly contains coenzyme forms (5′-deoxyadenosylcoblamin and methylcobalamin) of Vitamin B12 or hydroxocobalamin (or both). 
5. Edible Seaweeds A Source Of Essential Fatty Acids
Edible species of seaweed are generally low in fat, but provide a small quantity of healthy fats including essential fatty acids.
Interestingly, the FA(fatty acid) distribution of seaweed products showed high levels of n-3 FA and demonstrated a nutritionally ideal n-6/n-3 FA ratio.
The predominante FA in various seaweed products was eicosapentaenoic acid (C20:5, n-3) which was at concentrations as high as 50% of total FA content. 
6. Seaweeds Are Associated With Reduced All-Cause & CVD Mortality
Epidemiological evidence indicates that seaweed-containing diets are inversely associated with all-cause mortality and cardiovascular disease mortality in Japanese adults.
The information in this article has not been evaluated by the FDA and should not be used to diagnose, cure or treat any disease, implied or otherwise.