Iodine, Selenium, and Your Health

Iodine & running

Benefits of Dietary Iodine and Selenium

Selenium

Selenium is a nutrient that the body needs to stay healthy. According to the National Institutes of Health (NIH), Office of Dietary Supplements (ODS), selenium is important for reproduction, thyroid gland function, DNA production, and protecting the body from damage caused by free radicals and from infection.[1]

What is Iodine?

Iodine is a mineral the body needs to make thyroid hormones which control the body’s metabolism and many other important functions. The ODS fact sheet for iodine states that the body also needs thyroid hormones for proper bone and brain development during pregnancy and infancy. Getting enough iodine is important for everyone, especially infants and women who are pregnant.[2] 

How do Selenium and Iodine Work Together?

Selenium and iodine have a synergistic relationship that is especially important for a healthy thyroid. Iodine is a component of thyroid hormone, and selenium as a selenoprotein helps to convert the thyroid hormone into its active form. Both are needed by the thyroid in adequate amounts; too much of one can contribute to a deficiency of the other.[3]  They are both important for a healthy body, especially for heart health and thyroid function.

Iodine, Selenium, and Heart health

Selenium is necessary for proper cardiovascular function.  Selenium deficiency has been associated with multiple cardiovascular diseases, including myocardial infarction, heart failure, coronary heart disease, and atherosclerosis.[4]  Iodine deficiency that leads to hypothyroidism can disrupt normal metabolic functions such as heart rate. [5] 


Selenium, Iodine, and Thyroid function.

Most people in the United States and Canada get sufficient iodine in their diet.  Without enough iodine your body cannot make enough thyroid hormone which can cause many problems. Severe iodine deficiency in a pregnant woman can cause problems with her baby. Less severe iodine deficiency can cause lower-than-average IQ in infants and children and can decrease adults’ ability to work and think clearly.[6]  Iodine deficiency that leads to hypothyroidism can produce symptoms such as fatigue, weakness, sensitivity to cold, constipation, dry skin and hair, and weight gain.[7]  

    Risk Factors for Iodine and Selenium Deficiency

    While most people living in the United States get enough iodine and selenium in their diet, some other populations do not.  People with certain illnesses or living under certain conditions may have difficulty getting enough. 

    • Potential causes of selenium deficiency. People undergoing kidney dialysis (dialysis can remove selenium and lowered food intake can reduce selenium intake), people with HIV (from decreased appetite or malabsorption from diarrhea), and people who eat only local foods grown in soil with little selenium.[8]
    • Potential causes of iodine deficiency. People who do not use iodized salt (specialty salts, such as sea salt, kosher salt, Himalayan salt and fleur de sel are not usually iodized). Pregnant women need about half again as much iodine as other adults to provide adequate amounts of iodine for their baby. Vegans and others who eat little seafood, eggs, dairy products. People who eat only local foods grown in soil with low iodine levels (e.g., in the high mountains of the Alps, Andes, Himalayas). Another potential cause of iodine deficiency that is not common in the United States is that some people who barely ingest enough iodine and eat foods that interfere with the way iodine is used by their body (goitrogens).  Goitrogens include cruciferous vegetables (e.g., cabbage, cauliflower, brussels sprouts and broccoli). [9]

    Food vs. supplements

    The Dietary Guidelines for Americans says that we should get most of our nutrients from foods that contain vitamins, minerals, dietary fiber, and other nutrients.  Many foods contain iodine and selenium and most Americans get enough of both in their diets.

    Recommended Dietary Allowance of Selenium and Iodine

    Adult (19 years +)

    Selenium RDA[10]

    Iodine RDA[11]

    Men and Women

    55 mcg

    150 mcg

    Pregnant women

    60 mcg

    220 mcg

    Lactating women

    70 mcg

    290 mcg

    Iodine is found in soil and the ocean. The amount of iodine found in animal proteins and seaweed depends on how much is in the water where the seafood and seaweed are found.  Good sources of iodine are fish and shellfish, seaweed, iodized table salt, and to a lesser extent dairy, eggs, and chicken.

    Many foods contain selenium.  How much selenium is in plants depends on how much is in the soil and the amount of selenium in animal products depends on the animal food. You can get the recommended amount of selenium from seafood, meat, poultry, eggs, dairy products, breads, cereals, and other grain products.

    Halibut with lentils

    "Halibut on lentils with chard" by sporkist is licensed under CC BY 2.0.

    Selenium and Iodine Found in Food

     

    Serving size

    Selenium[12]

    Iodine[13]

    Baked beans

    1 cup

    13 mcg

    .8 mcg

    Bananas

    1 cup

    2 mcg

    .4 mcg

    Beef

    3 oz

    31 mcg

    4 mcg

    Brazil nuts

    1 oz (6-8 nuts)

    544 mcg

     

    Brown rice

    1 cup

    19 mcg

    .8 mcg

    Chicken

    3 oz

    22-25 mcg

    1.7 mcg

    Cottage cheese

    1 cup

    20 mcg

    78 mcg

    Eggs

    1 hard-boiled egg

    20 mcg

    26 mcg

    Fin fish and shellfish

    See table below

     

    Ham

    3 oz

    42 mcg

    1.2 mcg

    Iodized salt

    ½ tsp

    --

    152 mcg[14]

    Milk

    1 cup

    8 mcg

    84 mcg

    Mushrooms

    100 g

    12 mcg

    .34 mcg

    Oatmeal

    1 cup

    13 mcg

    .7 mcg

    Spinach (cooked)

    1 cup

    11mcg

    7 mcg

    Sunflower seeds

    ¼ cup

    19 mcg

    .1 mcg

    Turkey breast

    3 oz

    33 mcg

    1.8 mcg

    Yogurt

    1 cup

    8 mcg

    116 mcg

     

    Selenium and Iodine Found in Seafood

    Seafood type

    Serving size

    Selenium[15]

    Serving size

    Iodine[16]

    Atlantic cod

    3.5 oz

    38 mcg

    3 oz

    158 mcg

    Atlantic, coho salmon

    3.5 oz

    47, 46 mcg

    3 oz

    14 mcg

    Haddock

    3.5 oz

    43 mcg

    4 oz

    250 mcg

    Halibut

    3.5 oz

    55 mcg

    4 oz

    9 mcg

    Lobster

    3.5 oz

    73 mcg

    3 oz

    157 mcg

    Mussels

    3.5 oz

    90 mcg

     

     

    Octopus

    3.5 oz

    90 mcg

     

     

    Oysters  

    3.5 oz

    154 mcg

    3 oz

    93 mcg

    Sablefish

    3.5 oz

    47 mcg

     

     

    Seaweed (dried Nori)

     

     

    2 Tbsp

    116 mcg

    Shrimp

    3.5 oz

    50 mcg

    4 oz

    16 mcg

    Yellowfin tuna

    3.5 oz

    108 mcg

    3 oz

    17 mcg

     

     

    As you can see from the tables above, eating a seafood-rich diet is an easy and healthy way to get all the iodine and selenium your body needs. Sizzlefish can deliver your favorite source of nutrients in perfect portions. 

     

    Warning:  You Can Get Too Much

    The Tolerable Upper Intake Level is the maximum daily intake unlikely to cause harmful effects on health.

    Iodine:  The UL for iodine for all adults 19+ years of age and pregnant and lactating women is 1,100 micrograms. A very large dose of iodine (several grams) can cause burning of the mouth, throat, and stomach; fever; stomach pain; nausea; vomiting; diarrhea; weak pulse; and coma.[1] 

    Selenium:  The UL for selenium for all adults 19+ years of age and pregnant and lactating women is 400 micrograms daily. Chronically high intakes of selenium can lead to health problems, ranging from muscle tremors, hair loss, stomach upset, and lightheadedness, to more severe outcomes of heart attack, respiratory distress, or kidney failure. Brazil nuts are exceptionally high in selenium even when grown in low-selenium soil, with even one nut containing more than the RDA. Eating too many of these nuts daily can reach a toxic level, as can using supplements that contain selenium over the RDA.  Early symptoms include a metallic taste, bad breath; nausea, diarrhea; hair loss; nail brittleness or discoloration; skin rash or lesions; skin flushing; fatigue; irritability; and muscle tenderness.[1]

     

    References

     

    [1]  https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/

    [2]  https://ods.od.nih.gov/factsheets/Iodine-Consumer/

    [3]  https://www.hsph.harvard.edu/nutritionsource/selenium/

    [4]  Shimada, B.K., Alfulaij, N., and Seale, L.A. (2021). The Impact of Selenium Deficiency on Cardiovascular Function. Int J Mol Sci. 2021 Oct 2;22(19):10713. https://doi.org/10.3390/ijms221910713

    [5]  The trace elements iodine and selenium are essential for thyroid gland functioning and thyroid hormone biosynthesis and metabolism. While iodine is needed in the two major thyroid hormones triiodo-L-thyronine (T3) and tetraiodo-L-thyronine (T4), selenium is essential for the biosynthesis and function of a small number of selenocysteine (Sec)-containing selenoproteins implicated in thyroid hormone metabolism and gland function.  Schomburg, L. and Köhrle, J. (2008). On the importance of selenium and iodine metabolism for thyroid hormone biosynthesis and human health. Mol Nutr Food Res. 2008 Nov;52(11):1235-46. https://doi.org/10.1002/mnfr.200700465

    [6]  https://ods.od.nih.gov/factsheets/Iodine-Consumer/

    [7]  https://www.hsph.harvard.edu/nutritionsource/iodine/

    [8]  https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/

    [9]  https://ods.od.nih.gov/factsheets/Iodine-Consumer/

    [10]  https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/

    [11]  https://www.hsph.harvard.edu/nutritionsource/iodine/

    [12]   https://www.healthline.com/health/selenium-foods#bananas

    [13]   https://www.ars.usda.gov/arsuserfiles/80400535/data/iodine/iodine_database_release_2_per_serving.pdf

    [14]  https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/

    [15]  https://www.myfooddata.com/articles/foods-high-in-selenium.php

    [16]  https://www.ars.usda.gov/arsuserfiles/80400535/data/iodine/iodine_database_release_2_per_serving.pdf