Sea vegetables are virtually fat-free; low in calories; and rich in essential minerals, vitamins, protein, and important trace elements that are often lacking in land vegetables due to soil demineralization. "Sea vegetables contain more minerals than any other kind of food," claim Doctors Seibin and Teruko Arasaki, authors of Vegetables From the Sea. Analysis has shown that a wide range of minerals account for 7-38 percent of their dry weight. All of the elements essential to health - including calcium, sodium, magnesium, potassium, iodine, iron, and zinc - are present in sea vegetables in sufficient amounts. Of the wide variety of minerals present, calcium, iron, and iodine are of particular importance to people eating a dairy-free, grain-based vegetarian, or macrobiotic diet. For example, 1/4 cup of cooked hijiki contains over half the calcium found in a cup of milk and more iron than in an egg. Although iodine is, by nature, volatile and somewhat difficult to obtain, sea vegetables contain complex natural sugars that stabilize their iodine, making them excellent sources of this essential mineral.

Edible plants from the sea also contain important vitamins including vitamin A (in the form of beta-carotene), B1, B2, B6, niacin, vitamin C, pantothenic acid, and folic acid. Analysis has shown trace amounts of vitamin B12, which rarely occurs in land vegetables.

A study published in the American Journal of Clinical Nutrition suggests that strict vegetarian nursing mothers with low vitamin B12 levels get an acceptable source of this nutrient by consuming sea vegetables that are naturally high in B12. According to research, the relatively high vitamin B12 content of sea vegetables is thought to reflect a high level of vitamin B12-producing microorganisms in these plants.

For those watching their weight, sea vegetables are the perfect food. Their carbohydrates pass through the digestive system as complex fiber, cleansing the intestines while adding no calories to the diet.