Sea vegetables may be a better source of bioavailable iron than previously thought. One tablespoon of dried sea vegetable will contain between 1/2 milligram and 35 milligrams of iron, and this iron is also accompanied by a measurable amount vitamin C. Since vitamin C acts to increase the bioavailability of plant iron, this combination in sea vegetables may offer a special benefit.
Brown algae (including the commonly eaten sea vegetables kombu/kelp, wakame, and arame may be unique among the sea vegetables in their iodine content. Some species from the brown algae genus Laminaria are able to accumulate iodine in up to 30,000 times more concentrated a form than sea water!
Sea vegetables may be a unique food source not only of the mineral iodine, but also of the mineral vanadium. As part of their natural defense mechanisms, sea vegetables contain a variety of enzymes called haloperoxidases. These enzymes all require vanadium in order to function. Although this mineral is not as well known as some of the other mineral nutrients, it appears to play a multi-faceted role in regulation of carbohydrate metabolism and blood sugar. While research in this area is still in the preliminary stage and remains mixed in terms of results, vanadium may help to increase our body's sensitivity to insulin by inhibiting a group of enzymes called protein tyrosine phosphatases. It may also help us decrease our body's production of glucose and help us increase our body's ability to store starch in the form of glycogen.
Unlike some other types of vegetables, sea vegetables do not appear to depend on common polyphenol antioxidants (like carotenoids and flavonoids) for their total antioxidant capacity. Recent research from India makes it clear that a variety of non-flavonoid and non-carotenoid antioxidant compounds are present in sea vegetables, including several different types of antioxidant alkaloids.