Illuminating Iodine

Iodine is originally found in the earth’s crust. Over the years, flooding, leaching, and erosion have dwindled the bulk of iodine in the soil. Most iodine is formed along the coast. In nature, iodine is found in seaweed and other sea plants. In the areas where there are low levels of natural iodine, iodine fortified are the only sources of iodine.

The majority of iodine is stored in the thyroid. Its primary function is to help produce thyroid hormones. When iodine is lacking in the body, the thyroid gland suffers. The most common sign of an iodine deficiency is a goiter. A goiter is the enlargement of the thyroid gland. Another cause of low iodine levels involves lack of development. When pregnant mothers have low levels of iodine, their babies have a higher chance of experiencing cretinism, which is a physical and mental impairment. Pregnant women are most at risk for iodine deficiency.


The recommended dietary allowance (RDA) for iodine(1).

Life stage: RDA (mcg/day)

Infant 0–12 mo. : 110–130

1–8 years:90

9–13 years: 120

Adults >14 years: 150

Pregnant: 220

Lactating: 290


Breast cancer. Now researchers have seen a link between iodine deficiency and breast cancer. A deficiency in iodine increases estrogen levels which increases the chance of breast cancer. The Japanese have a one-third less chance of getting breast cancer than American women. The traditional Japanese diet contains seaweed, soy sauce, and miso. All have a very high level of salt, and therefore natural iodine. Japanese women consume 25 times more iodine than American women. This research shows the inverse relationship between iodine intake and breast cancer.

Weight gain. Thyroid hormones control metabolism. Research shows that a low level of thyroid hormones slows metabolism and has an influence on weight gain.

Heart Health. Weight gain has an effect on the heart. When iodine is lacking, hypothyroidism or low levels of thyroid hormone results. Hypothyroidism distorts the lipid profiles by increasing the bad LDL and total cholesterol levels. This increases the risk of heart-related diseases such as atherosclerosis. Also, low thyroid hormone makes the heart muscle delicate, and the heart will not compress as firmly which can cause cardiac arrhythmias(3).


Food source: Mcg Iodine

Seaweed (1/4 oz.): 4500

Iodized salt (1tsp.): 400

Cod (3 oz.): 99

Milk (1 cup): 56

Tuna (3 oz.): 17


Are you at risk for iodine deficiency? Iodine plays a critical role in the human body, specifically in the thyroid gland. The public needs to understand the importance of iodine in the daily diet. You can easily get the recommended intake of iodine without going overboard on your sodium by using iodized salt in your daily cooking!


  1. Zimmermann, Michael, and Paula R. Trumbo. “Iodine.” Advances in Nutrition: An International Review Journal 4, no. 2 (March 1, 2013): 262–64. doi:10.3945/an.113.003665.
  2. Leung, Angela M., Lewis E. Braverman, and Elizabeth N. Pearce. “History of U.S. Iodine Fortification and Supplementation.” Nutrients 4, no. 11 (November 13, 2012): 1740–46. doi:10.3390/nu4111740.

Originally published at