Asparagus is an "upscale" vegetable that combines a little too well with butter or creamy sauces such as hollandaise. It's been cultivated for thousands of years and contains lots of nutrients including iodine. Iodine is needed for healthy thyroid gland function, but the concentration found in vegetables is highly dependent on soil quality. Given the right growing conditions, asparagus can be a good source of iodine, but it’s not the richest vegetable source.
Iodine is needed to make the two main hormones, called thyroxine and triiodothyronine, produced by your thyroid. These hormones regulate your metabolism and largely determine how much energy you have. A lack of iodine results in a swollen thyroid, termed a goiter, and hormone imbalance. A chronic lack of thyroid hormones is diagnosed as hypothyroidism, which often leads to symptoms of extreme fatigue, weight gain, dry skin and depressed mood. In the United States, hypothyroidism is much more common in women and affects approximately 15 percent of the American population. The daily requirement for iodine is about 150 micrograms, although consuming much higher levels for extended periods of time can trigger an overproduction of thyroid hormone.
Asparagus stalks are actually the leaves of a plant native to most parts of Europe and northern Africa. Particularly fibrous and woody, asparagus needs to be cooked to be eaten and enjoyed. Asparagus is an especially good source of vitamin K, many B vitamins and iron. Cooking asparagus in boiling water destroys much of the iodine, so sauté the vegetable to preserve the iodine and most of the other nutrients. Some brands of canned asparagus may also be good sources if they contain iodized salt as a preservative.
Sea asparagus, also called pickleweed and glasswort, is actually a distant relative of spinach, although it looks like miniature asparagus stalks. Sea asparagus is commonly found in Hawaii, the Pacific Northwest, western Canada and Japan. It’s an intertidal plant, similar to kelp, which grows in brackish water near the edge of the ocean. Unlike most examples of terrestrial asparagus, sea asparagus is an excellent source of iodine as are many other sea vegetables.
Rich Sources of Iodine
Food naturally rich in iodine includes kelp, most other edible seaweeds, Jerusalem artichokes, fennel and potato skins. For example, some species of kelp contain up to 8,000 micrograms of iodine per gram. In addition to asparagus, other foods that can be good sources of iodine include spinach, Swiss chard, squash, soybeans, Lima beans, garlic cloves and strawberries. Iodine was added to table salt beginning in the 1920s to prevent goiter and thyroid dysfunction.
- Public Health Nutrition: From Principles to Practice; Mark Lawrence and Tony Worsley
- The Nutribase Complete Book of Food Counts; Art Ulene
- Encyclopedia of Human Nutrition; Benjamin Caballero et al.
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.